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Manual for extension shortcut.

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Drup 2016-02-02 18:17:51 +01:00
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manual/manual/refman/exten.etex
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@ -1706,7 +1706,8 @@ let f = function
\section{Extension nodes}\label{s:extension-nodes}
(Introduced in OCaml 4.02)
(Introduced in OCaml 4.02,
infix notations for constructs other than expressions added in 4.03)
Extension nodes are generic placeholders in the syntax tree. They are
rejected by the type-checker and are intended to be ``expanded'' by external
@ -1765,23 +1766,24 @@ class-field:
;
\end{syntax}
An infix form is available for extension nodes as expressions, when
the payload is a single expression. This form applies to all
expressions starting with one or two keywords: the first keyword
followed by the percent sign and then an extension identifier.
An infix form is available for extension nodes when
the payload is of the same kind
(expression with expression, pattern with pattern ...).
Examples:
\begin{verbatim}
let%foo x = 2 in x + 1 === [%foo let x = 2 in x + 1]
begin%foo ... end === [%foo begin ... end]
module%foo M = .. === [%%foo module M = ... ]
val%foo x : t === [%%foo: val x : t]
\end{verbatim}
When this form is used together with the infix syntax for attributes,
the attributes are considered to apply to the payload:
\begin{verbatim}
let%foo[@bar] x = 2 in x + 1 === [%foo (let x = 2 in x + 1) [@bar]]
fun%foo[@bar] x -> x + 1 === [%foo (fun x -> x + 1)[@foo ] ];
\end{verbatim}
\subsection{Built-in extension nodes}