forked from mirrors/nixpkgs
114 lines
2.9 KiB
XML
114 lines
2.9 KiB
XML
|
<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>
|
||
|
|
|
||
|
|
<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>
|
||
|
|
|
||
|
|
<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" "bearssl" ];
|
||
|
|
=> false
|
||
|
|
stderr> trace: sslLibrary must be one of "openssl", "libressl", but is: "bearssl"
|
||
|
|
]]></programlisting>
|
||
|
|
</example>
|
||
|
|
</section>
|
||
|
|
</section>
|