From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: X-Spam-Status: No, score=0.9 required=5.0 tests=AWL,DNS_FROM_RFC_ABUSE autolearn=disabled version=3.1.3 X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from mail1-relais-roc.national.inria.fr (mail1-relais-roc.national.inria.fr [192.134.164.82]) by yquem.inria.fr (Postfix) with ESMTP id 77318BBAF for ; Mon, 10 Aug 2009 15:22:30 +0200 (CEST) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhUEANy7f0qACH+TgWdsb2JhbACaTgEBFiSlQIVhiE6EGAWCNg X-IronPort-AV: E=Sophos;i="4.43,353,1246831200"; d="scan'208";a="34236629" Received: from server-nat-4.cs.umd.edu (HELO bacon.cs.umd.edu) ([128.8.127.147]) by mail1-smtp-roc.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-SHA; 10 Aug 2009 15:22:29 +0200 X-CSD-MailScanner-Watermark: 1250515341.20861@0Gnjd7Ujp+NK9qIjIWo2vQ Received: from veruca.cs.umd.edu (veruca.cs.umd.edu [128.8.128.211]) (authenticated bits=0) by bacon.cs.umd.edu (8.13.1/8.14.1) with ESMTP id n7ADMKKr023286 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO); Mon, 10 Aug 2009 09:22:20 -0400 Subject: Re: [Caml-list] Re: ocaml sefault in bytecode: unanswered questions From: Elnatan Reisner To: Alain Frisch Cc: Caml Mailing List In-Reply-To: <4A7F1EEF.2050301@frisch.fr> References: <000301ca184b$032b8cc0$0982a640$@chollet@free.fr> <000701ca184d$29507e90$7bf17bb0$@metastack.com> <001001ca18c7$37b22220$a7166660$@chollet@free.fr> <001501ca18cc$d59a61a0$80cf24e0$@metastack.com> <001201ca18e9$c4456810$4cd03830$@chollet@free.fr> <4A7ED53B.90607@frisch.fr> <32623A80-A2C3-4AE4-B9FA-3FC0888494BD@cs.umd.edu> <4A7F1EEF.2050301@frisch.fr> Content-Type: text/plain Date: Mon, 10 Aug 2009 09:22:19 -0400 Message-Id: <1249910539.27080.10.camel@veruca.cs.umd.edu> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-41.el4_7.2) Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0 (bacon.cs.umd.edu [172.24.3.34]); Mon, 10 Aug 2009 09:22:20 -0400 (EDT) X-Spam: no; 0.00; ocaml:01 bytecode:01 0200,:01 frisch:01 mutable:01 symmetric:01 toplevel:01 arrays:01 recursive:01 pointers:01 bool:01 2009:98 2009:98 equality:01 terminates:01 On Sun, 2009-08-09 at 21:09 +0200, Alain Frisch wrote: > On 8/9/2009 8:56 PM, Elnatan Reisner wrote: > > My other issue is that the description of (==) for mutable structures > > doesn't specify that it is symmetric; reading the documentation > > literally only implies that e1 is a substructure of e2. Even just adding > > 'and vice versa' might clean this up: > > |e1 == e2| is true if and only if physical modification of |e1| also > > affects |e2 and vice versa| > > It depends on what 'physical modification' and 'affect' mean. Clearly, > the documentation means toplevel modifications of the values (i.e. > modifying fields for record values, or elements for arrays or strings). > If one includes deep modifications, then your extended criterion does > not work either (think about two mutually recursive records). You're right; thanks for pointing this out. But what does this mean for physical equality? What does it really mean? Does [e1 == e2] mean e1 and e2 are the same entity in memory---i.e., they are equal as C pointers? > Note that (=) sometimes terminates for cylic values. > > # type t = A of t | B of t;; > type t = A of t | B of t > # (let rec x = A x in x) = (let rec x = B x in x);; > - : bool = false Again, thanks for pointing this out. But can (=) ever evaluate to true on cyclic structures? -Elnatan