summary refs log tree commit diff
path: root/doc/functions/library/asserts.xml
diff options
context:
space:
mode:
authorAlyssa Ross <hi@alyssa.is>2022-05-31 09:59:33 +0000
committerAlyssa Ross <hi@alyssa.is>2022-05-31 09:59:57 +0000
commit9ff36293d1e428cd7bf03e8d4b03611b6d361c28 (patch)
tree1ab51a42b868c55b83f6ccdb80371b9888739dd9 /doc/functions/library/asserts.xml
parent1c4fcd0d4b0541e674ee56ace1053e23e562cc80 (diff)
parentddc3c396a51918043bb0faa6f676abd9562be62c (diff)
downloadnixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar.gz
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar.bz2
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar.lz
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar.xz
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.tar.zst
nixpkgs-9ff36293d1e428cd7bf03e8d4b03611b6d361c28.zip
Last good Nixpkgs for Weston+nouveau? archive
I came this commit hash to terwiz[m] on IRC, who is trying to figure out
what the last version of Spectrum that worked on their NUC with Nvidia
graphics is.
Diffstat (limited to 'doc/functions/library/asserts.xml')
-rw-r--r--doc/functions/library/asserts.xml112
1 files changed, 112 insertions, 0 deletions
diff --git a/doc/functions/library/asserts.xml b/doc/functions/library/asserts.xml
new file mode 100644
index 00000000000..7c94222ef13
--- /dev/null
+++ b/doc/functions/library/asserts.xml
@@ -0,0 +1,112 @@
+<section xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="sec-functions-library-asserts">
+ <title>Assert functions</title>
+
+ <section xml:id="function-library-lib.asserts.assertMsg">
+  <title><function>lib.asserts.assertMsg</function></title>
+
+  <subtitle><literal>assertMsg :: Bool -> String -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.asserts.assertMsg" />
+
+  <para>
+   Print a trace message if <literal>pred</literal> is false.
+  </para>
+
+  <para>
+   Intended to be used to augment asserts with helpful error messages.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>pred</varname>
+    </term>
+    <listitem>
+     <para>
+      Condition under which the <varname>msg</varname> should <emphasis>not</emphasis> be printed.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>msg</varname>
+    </term>
+    <listitem>
+     <para>
+      Message to print.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.asserts.assertMsg-example-false">
+   <title>Printing when the predicate is false</title>
+<programlisting><![CDATA[
+assert lib.asserts.assertMsg ("foo" == "bar") "foo is not bar, silly"
+stderr> trace: foo is not bar, silly
+stderr> assert failed
+]]></programlisting>
+  </example>
+ </section>
+
+ <section xml:id="function-library-lib.asserts.assertOneOf">
+  <title><function>lib.asserts.assertOneOf</function></title>
+
+  <subtitle><literal>assertOneOf :: String -> String ->
+      StringList -> Bool</literal>
+  </subtitle>
+
+  <xi:include href="./locations.xml" xpointer="lib.asserts.assertOneOf" />
+
+  <para>
+   Specialized <function>asserts.assertMsg</function> for checking if <varname>val</varname> is one of the elements of <varname>xs</varname>. Useful for checking enums.
+  </para>
+
+  <variablelist>
+   <varlistentry>
+    <term>
+     <varname>name</varname>
+    </term>
+    <listitem>
+     <para>
+      The name of the variable the user entered <varname>val</varname> into, for inclusion in the error message.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>val</varname>
+    </term>
+    <listitem>
+     <para>
+      The value of what the user provided, to be compared against the values in <varname>xs</varname>.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry>
+    <term>
+     <varname>xs</varname>
+    </term>
+    <listitem>
+     <para>
+      The list of valid values.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+
+  <example xml:id="function-library-lib.asserts.assertOneOf-example">
+   <title>Ensuring a user provided a possible value</title>
+<programlisting><![CDATA[
+let sslLibrary = "bearssl";
+in lib.asserts.assertOneOf "sslLibrary" sslLibrary [ "openssl" "libressl" ];
+=> false
+stderr> trace: sslLibrary must be one of "openssl", "libressl", but is: "bearssl"
+        ]]></programlisting>
+  </example>
+ </section>
+</section>