From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 7A392BC48 for ; Mon, 18 Apr 2005 14:11:24 +0200 (CEST) Received: from smtp06.web.de (smtp06.web.de [217.72.192.224]) by concorde.inria.fr (8.13.0/8.13.0) with ESMTP id j3ICBOaw019905 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO) for ; Mon, 18 Apr 2005 14:11:24 +0200 Received: from [217.235.113.81] (helo=wiko) by smtp06.web.de with smtp (WEB.DE 4.104 #268) id 1DNV60-0004HF-00 for caml-list@yquem.inria.fr; Mon, 18 Apr 2005 14:11:21 +0200 Message-ID: <001901c5440f$ce1a5e80$14b2a8c0@wiko> From: "Andreas Rossberg" To: References: <42637B63.1070608@ifp.fr> <200504181227.07108.jon@ffconsultancy.com> Subject: Re: [Caml-list] type of == Date: Mon, 18 Apr 2005 14:11:51 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Sender: AndreasRossberg@web.de X-Sender: AndreasRossberg@web.de X-Miltered: at concorde with ID 4263A3EC.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Spam: no; 0.00; rossberg:01 caml-list:01 bool:01 abstraction:01 cheers:01 equality:01 equality:01 polymorphic:01 andreas:01 andreas:01 argument:01 represented:02 latter:03 depend:07 break:07 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on yquem.inria.fr X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.0.2 X-Spam-Level: Jon Harrop : > > If there were an "'a -> 'b -> bool" physical equality test, how could it ever > return "true"? Either when 'a and 'b happen to be instantiated to the same type, or when the representation happens to be the same, e.g. 0 == false. The latter also provides a good argument against making physical equality too polymorphic. It would break abstraction, much worse than it does already. In particular, a program's meaning could depend on implementation details (like false being represented by 0) in very questionable ways. Cheers, - Andreas