forked from lix-project/lix
Document functors
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@ -196,6 +196,24 @@ in concat { x = "foo"; y = "bar"; }</programlisting>
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</para>
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<para>A set that has a <literal>__functor</literal> attribute whose value
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is callable (i.e. is itself a function or a set with a
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<literal>__functor</literal> attribute whose value is callable) can be
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applied as if it were a function, with the set itself passed in first
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, e.g.,
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<programlisting>
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let add = { __functor = self: x: x + self.x; };
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inc = add // { x = 1; };
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in inc 1
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</programlisting>
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evaluates to <literal>2</literal>. This can be used to attach metadata to a
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function without the caller needing to treat it specially, or to implement
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a form of object-oriented programming, for example.
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</para>
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</simplesect>
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