From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <pierre.weis@inria.fr>
Delivered-To: caml-list@yquem.inria.fr
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39])
	by yquem.inria.fr (Postfix) with ESMTP id A5AC3BC8E
	for <caml-list@yquem.inria.fr>; Tue, 15 Feb 2005 23:19:55 +0100 (CET)
Received: from pauillac.inria.fr (pauillac.inria.fr [128.93.11.35])
	by concorde.inria.fr (8.13.0/8.13.0) with ESMTP id j1FMJt6T012931
	for <caml-list@yquem.inria.fr>; Tue, 15 Feb 2005 23:19:55 +0100
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id XAA11621 for <caml-list@pauillac.inria.fr>; Tue, 15 Feb 2005 23:19:54 +0100 (MET)
Received: from distrib3.mail.u-psud.fr (distrib3.mail.u-psud.fr [129.175.34.155])
	by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id j1FMJsju020219
	for <caml-list@inria.fr>; Tue, 15 Feb 2005 23:19:54 +0100
Received: from intfiltre2.mail.u-psud.fr (intfiltre2.mail.u-psud.fr [129.175.34.150])
	by distrib3.mail.u-psud.fr (8.12.10/8.12.0.Beta10) with ESMTP id j1FMJtmB025364
	for <caml-list@inria.fr>; Tue, 15 Feb 2005 23:19:55 +0100
Received: from post1.mail.u-psud.fr (post1.mail.u-psud.fr [129.175.34.87])
	by intfiltre2.mail.u-psud.fr (8.12.10/8.12.0.Beta10) with ESMTP id j1FMJRM4015852
	for <caml-list@inria.fr>; Tue, 15 Feb 2005 23:19:54 +0100
Received: from tahiti.ile.u-psud.fr (tahiti.ile.u-psud.fr [172.17.4.7])
	by post1.mail.u-psud.fr (8.12.10/8.12.0.Beta10) with ESMTP id j1FMHjeZ015171
	for <caml-list@inria.fr>; Tue, 15 Feb 2005 23:17:45 +0100
Received: from laposte.net (Naoned.ile.u-psud.fr [172.17.4.237])
	by tahiti.ile.u-psud.fr (Postfix) with ESMTP id 863823CDA18
	for <caml-list@inria.fr>; Tue, 15 Feb 2005 23:17:19 +0100 (CET)
Message-ID: <421275ED.1060607@laposte.net>
Date: Tue, 15 Feb 2005 23:21:33 +0100
From: =?ISO-8859-1?Q?Olivier_P=E9r=E8s?= <olivier.peres@laposte.net>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; fr; rv:1.6) Gecko/20040115
X-Accept-Language: br, fr, en
MIME-Version: 1.0
To: Caml-list <caml-list@inria.fr>
Subject: Re: [Caml-list] Polymorphic variant typing
References: <7bf1f3b95c18eeda0ed169eb7f73d6f0@urbanet.ch>
In-Reply-To: <7bf1f3b95c18eeda0ed169eb7f73d6f0@urbanet.ch>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
X-Scanned: by amavis
X-Miltered: at concorde with ID 4212758B.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Miltered: at nez-perce with ID 4212758A.001 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Spam: no; 0.00; caml-list:01 ocaml:01 val:01 peres:98 peres:98 ...:98 polymorphic:01 typing:01 int:01 int:01 match:02 match:02 variant:02 types:02 float:03 
X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on yquem.inria.fr
X-Spam-Status: No, score=0.1 required=5.0 tests=FORGED_RCVD_HELO 
	autolearn=disabled version=3.0.2
X-Spam-Level: 

Gilles Dubochet a écrit :

> let incr g x = match x with
>     | `Int i -> `Int (i+1)
>     | x -> (g x);;
> 
> Receives type:
> (([> `Int of int ] as 'a) -> ([> `Int of int ] as 'b)) -> 'a -> 'b

    Now, how about this :

let incr x g = match x with
   | `Int i -> `Int (i+1)
   | x -> g x;;

    Doesn't it look like your code ? OCaml 3.08.2 types it as follows :
val incr : ([> `Int of int ] as 'a) -> ('a -> ([> `Int of int ] as 'b)) 
-> 'b = <fun>

    This is more like it !

incr (`Int 1) (fun (`Int i) -> (`Int (i+1)));;
- : [> `Int of int ] = `Int 2

incr (`Float 1.0) (fun x -> match x with (`Float f) -> (`Float (f +. 
1.0)) | x -> x);;
- : [> `Float of float | `Int of int ] = `Float 2.

    It remains to understand why the type of incr should depend upon the 
order in which the arguments are given...

    Yours,

    Olivier.