diff options
| -rw-r--r-- | doc/manual/expressions/language-constructs.xml | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/doc/manual/expressions/language-constructs.xml b/doc/manual/expressions/language-constructs.xml index ddb3498946b7..74809bb412d3 100644 --- a/doc/manual/expressions/language-constructs.xml +++ b/doc/manual/expressions/language-constructs.xml @@ -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> |