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doc: document lib.makeOverridable

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Luca Bruno 2015-06-30 12:19:49 +02:00
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doc/functions.xml
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@ -85,4 +85,36 @@ in ...</programlisting>
</section>
<section xml:id="sec-lib-makeOverridable">
<title>lib.makeOverridable</title>
<para>
The function <varname>lib.makeOverridable</varname> is used make the result
of a function easily customizable. This utility only makes sense for functions
that accept an argument set and return an attribute set.
</para>
<para>
Example usage:
<programlisting>f = { a, b }: { result = a+b; }
c = lib.makeOverridable f { a = 1; b = 2; }</programlisting>
</para>
<para>
The variable <varname>c</varname> is the value of the <varname>f</varname> function
applied with some default arguments. Hence the value of <varname>c.result</varname>
is <literal>3</literal>, in this example.
</para>
<para>
The variable <varname>c</varname> however also has some additional functions, like
<link linkend="sec-pkg-override">c.override</link> which can be used to
override the default arguments. In this example the value of
<varname>(c.override { a = 4; }).result</varname> is 6.
</para>
</section>
</chapter>