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What does underscore mean in this type expression?
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Date: -- (:)
From: Christophe TROESTLER <Christophe.Troestler+ocaml@u...>
Subject: Re: [Caml-list] What does underscore mean in this type expression?
On Sat, 30 Aug 2008 12:27:18 +0100, Richard Jones wrote:
> 
>     val get_domains :
>       (_[> `R ] as 'a) Connect.t ->
>   is not included in
>     val get_domains :
>       ([> `R ] as 'a) Connect.t ->
> 
> This syntax doesn't appear to be documented in the manual (unless it's
> related to '_a).  What does it mean?

It is a weak type as you guessed.  To convince you of that, here is
some code:

# let x = ref `X;;
val x : _[> `X ] ref = {contents = `X}

Cheers,
C.