Chapter 8 Language extensions

This chapter describes language extensions and convenience features that are implemented in OCaml, but not described in the OCaml reference manual.

4 Local opens for patterns

(Introduced in OCaml 4.04)

pattern	::=	...
	∣	module-path .( pattern )
	∣	module-path .[ pattern ]
	∣	module-path .[\| pattern \|]
	∣	module-path .{ pattern }

For patterns, local opens are limited to the module-path.( pattern) construction. This construction locally open the module referred to by the module path module-path in the scope of the pattern pattern.

When the body of a local open pattern is delimited by [ ], [| |], or { }, the parentheses can be omitted. For example, module-path.[ pattern] is equivalent to module-path.([ pattern]), and module-path.[| pattern |] is equivalent to module-path.([| pattern |]).

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