From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <avaron@gmail.com>
X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr
X-Spam-Level: **
X-Spam-Status: No, score=2.1 required=5.0 tests=AWL,DNS_FROM_RFC_ABUSE,
	SPF_NEUTRAL autolearn=disabled version=3.1.3
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78])
	by yquem.inria.fr (Postfix) with ESMTP id 8D5D0BB83
	for <caml-list@yquem.inria.fr>; Sun,  3 Sep 2006 03:22:59 +0200 (CEST)
Received: from wx-out-0506.google.com (wx-out-0506.google.com [66.249.82.234])
	by nez-perce.inria.fr (8.13.6/8.13.6) with ESMTP id k831Mwdu020969
	for <caml-list@yquem.inria.fr>; Sun, 3 Sep 2006 03:22:59 +0200
Received: by wx-out-0506.google.com with SMTP id s6so1601935wxc
        for <caml-list@yquem.inria.fr>; Sat, 02 Sep 2006 18:22:58 -0700 (PDT)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
        s=beta; d=gmail.com;
        h=received:in-reply-to:references:mime-version:content-type:message-id:cc:content-transfer-encoding:from:subject:date:to:x-mailer;
        b=dxMz5ioZ4z7S6+y1IFIz//TcE4/FFcyyN39gfkojcJIFkO/BblHdNdhrIdwsnQSIraCVdd9UVLMjYjSSxOgDDp8MGmdmJsLqRCl4vpRWUcn6qa6bzkgLFZnZi8ButXDXkYpd3eaiwsaBAnuBD1SIEO9JSB7QlyHKKRJWjhWMQks=
Received: by 10.70.117.3 with SMTP id p3mr6459507wxc;
        Sat, 02 Sep 2006 18:22:58 -0700 (PDT)
Received: from ?192.168.0.3? ( [70.19.59.48])
        by mx.gmail.com with ESMTP id h20sm5599587wxd.2006.09.02.18.22.57;
        Sat, 02 Sep 2006 18:22:57 -0700 (PDT)
In-Reply-To: <20060902.201646.110439764.garrigue@math.nagoya-u.ac.jp>
References: <012901c6cdec$64edf490$6a7ba8c0@treble> <1157138993.22787.34.camel@rosella.wigram> <7E1CAC5D-67CC-4A5C-8DE6-BB2A60A6615B@gmail.com> <20060902.201646.110439764.garrigue@math.nagoya-u.ac.jp>
Mime-Version: 1.0 (Apple Message framework v752.2)
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Message-Id: <C90730C4-FF32-4C53-A177-7385E56BB4F6@gmail.com>
Cc: caml-list@yquem.inria.fr
Content-Transfer-Encoding: 7bit
From: Andres Varon <avaron@gmail.com>
Subject: Re: [Caml-list] Polymorphic variants question
Date: Sat, 2 Sep 2006 21:22:55 -0400
To: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
X-Mailer: Apple Mail (2.752.2)
X-j-chkmail-Score: MSGID : 44FA2E72.000 on nez-perce : j-chkmail score : X : 0/20 1
X-Miltered: at nez-perce with ID 44FA2E72.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Spam: no; 0.00; variants:01 struct:01 struct:01 variants:01 functor:01 2006,:98 wrote:01 polymorphic:01 polymorphic:01 abstract:01 caml-list:01 functions:01 int:01 match:02 string:02 


On Sep 2, 2006, at 7:16 AM, Jacques Garrigue wrote:

> Just that the concrete type is much simpler.
> The abstract type does not work directly, as you need a way to ensure
> that B.t and C.t are compatible. Otherwise, one could write
>
> module D = A(struct type t = [ `A of int] ... end)
>             (struct type t = [ `A of string] ... end)
>
> which is clearly incorrect.

I use a more restricted version of polymorphic variants to ensure  
that two functions that are being composed through a match in the  
style of the question do not share a tag (and so one function will  
not override the expected behavior of the second one), even if the  
tags are fully compatible; being this the case, your example cannot  
occur.

I am not an expert in programming languages, and I cannot see - in  
this restricted case - a reason why that functor could still be  
problematic. Is there some?

Thanks!

Andres