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nixpkgs docs: document zipAttrsWith

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Graham Christensen 2018-10-12 16:26:56 -04:00
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doc/functions/library/attrsets.xml
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@ -1441,4 +1441,83 @@ lib.attrsets.zipAttrsWithNames
]]></programlisting>
</example>
</section>
<section xml:id="function-library-lib.attrsets.zipAttrsWith">
<title><function>lib.attrsets.zipAttrsWith</function></title>
<subtitle><literal>zipAttrsWith :: (String -> [ Any ] -> Any) -> [ AttrSet ] -> AttrSet</literal>
</subtitle>
<xi:include href="./locations.xml" xpointer="lib.attrsets.zipAttrsWith" />
<para>
Merge sets of attributes and use the function <varname>f</varname> to merge
attribute values. Similar to <xref
linkend="function-library-lib.attrsets.zipAttrsWithNames" /> where
all key names are passed for <varname>names</varname>.
</para>
<variablelist>
<varlistentry>
<term>
<varname>f</varname>
</term>
<listitem>
<para>
<literal>(String -> [ Any ] -> Any</literal>
</para>
<para>
Accepts an attribute name, all the values, and returns a combined value.
</para>
<variablelist>
<varlistentry>
<term>
<varname>name</varname>
</term>
<listitem>
<para>
The name of the attribute each value came from.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>vs</varname>
</term>
<listitem>
<para>
A list of values collected from the list of attribute sets.
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>sets</varname>
</term>
<listitem>
<para>
A list of attribute sets to zip together.
</para>
</listitem>
</varlistentry>
</variablelist>
<example xml:id="function-library-lib.attrsets.zipAttrsWith-example">
<title>Summing a list of attribute sets of numbers</title>
<programlisting><![CDATA[
lib.attrsets.zipAttrsWith
(name: vals: "${name} ${toString (builtins.foldl' (a: b: a + b) 0 vals)}")
[
{ a = 1; b = 1; c = 1; }
{ a = 10; }
{ b = 100; }
{ c = 1000; }
]
=> { a = "a 11"; b = "b 101"; c = "c 1001"; }
]]></programlisting>
</example>
</section>
</section>