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Diffstat (limited to 'doc/manual/expressions/language-values.xml')
| -rw-r--r-- | doc/manual/expressions/language-values.xml | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/doc/manual/expressions/language-values.xml b/doc/manual/expressions/language-values.xml index f1174ecb5d8d..b90baac5054c 100644 --- a/doc/manual/expressions/language-values.xml +++ b/doc/manual/expressions/language-values.xml @@ -276,6 +276,23 @@ added to the set: This will evaluate to <literal>{}</literal> if <literal>foo</literal> evaluates to <literal>false</literal>.</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> |