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extended args@ explanation

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Joachim Schiele 2015-07-07 02:09:50 +02:00
parent dd48c06bb6
commit 8ce96becf0
1 changed files with 10 additions and 4 deletions
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14
doc/manual/expressions/language-constructs.xml
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@ -177,13 +177,19 @@ map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
<listitem><para>An <literal>@</literal>-pattern provides a means of referring <listitem><para>An <literal>@</literal>-pattern provides a means of referring
to the whole value being matched: to the whole value being matched:
<programlisting> <programlisting> args@{ x, y, z, ... }: z + y + x + args.a</programlisting>
args@{ x, y, z, ... }: z + y + x + args.a</programlisting>
but can also be written as:
<programlisting> { x, y, z, ... } @ args: z + y + x + args.a</programlisting>
Here <varname>args</varname> is bound to the entire argument, which Here <varname>args</varname> is bound to the entire argument, which
is further matched against the pattern <literal>{ x, y, z, is further matched against the pattern <literal>{ x, y, z,
... }</literal>.</para></listitem> ... }</literal>. This <literal>@</literal>-pattern makes mainly sense with an
ellipsis(<literal>...</literal>) as you can now access attribute names as
<literal>a</literal>, using <literal>args.a</literal>, which was given as an
additional attribute to the function.
</para></listitem>
</itemizedlist> </itemizedlist>