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To: pfitzen@informatik.uni-tuebingen.de
Cc: caml-list@inria.fr
Subject: Re: # and polymorphic variants
In-Reply-To: <200102010037.BAA12641@sunstroke.informatik.uni-tuebingen.de>
References: <200102010037.BAA12641@sunstroke.informatik.uni-tuebingen.de>
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Message-Id: <20010201233110I.garrigue@kurims.kyoto-u.ac.jp>
Date: Thu, 01 Feb 2001 23:31:10 +0900
From: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
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From: Juergen Pfitzenmaier <pfitzen@informatik.uni-tuebingen.de>

> Dear ocaml users,
> consider the following example:
> 
> type t1 = [ `A of int ];;
> type t2 = [ `B of string ];;
> type t = [ `A of int | `B of string ];;
> 
> let f1 (`A (x : int)) =
> 	print_int x
> and f2 (`B (x : string)) =
> 	print_string x
> and f (x : t) =
> 	match x with
> 	| #t1 -> f1 x      (* this is not allowed !! *)
> 	| #t2 -> f2 x;;
...
> But I would like to see something clean like giving a name to the # pattern
>     ...
> 	match x with
> 	| #t1 y -> f1 y    (* (y : t1) would have the same value as x *)

You were pretty close to the solution !
You just have to write
        match x with
        | #t1 as y -> f1 y
        | #t2 as y -> f2 y

logical, no?

         Jacques