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Document functors

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This commit is contained in:
Shea Levy 2014-10-15 22:32:08 -04:00
parent 997defa166
commit 3d604ac88c
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18
doc/manual/expressions/language-constructs.xml
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@ -196,6 +196,24 @@ in concat { x = "foo"; y = "bar"; }</programlisting>
</para>
<para>A set that has a <literal>__functor</literal> attribute whose value
is callable (i.e. is itself a function or a set with a
<literal>__functor</literal> attribute whose value is callable) can be
applied as if it were a function, with the set itself passed in first
, e.g.,
<programlisting>
let add = { __functor = self: x: x + self.x; };
inc = add // { x = 1; };
in inc 1
</programlisting>
evaluates to <literal>2</literal>. This can be used to attach metadata to a
function without the caller needing to treat it specially, or to implement
a form of object-oriented programming, for example.
</para>
</simplesect>