220 4868 article Path: news.gmane.org!not-for-mail From: Zhihao Yuan Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: std::sequence Date: Tue, 4 Jun 2013 20:17:06 -0400 Lines: 30 Approved: news@gmane.org Message-ID: References: <4551abbc-43aa-4520-a91a-f8eb25a90588@isocpp.org> <2c8e6079-9c87-425a-93e2-39251df57cd8@isocpp.org> <9f1cace3-0503-4a3c-a8ce-d7546564b3ef@isocpp.org> <1c991e6e-6bc3-4822-9ffd-7f2508e63974@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1370391429 17691 80.91.229.3 (5 Jun 2013 00:17:09 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 00:17:09 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCUILMGRQMARBBEHXKGQKGQE3UT4XUQ@isocpp.org Wed Jun 05 02:17:10 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ee0-f72.google.com ([74.125.83.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk1PZ-0007vs-LS for gclcip-std-proposals@m.gmane.org; Wed, 05 Jun 2013 02:17:09 +0200 Original-Received: by mail-ee0-f72.google.com with SMTP id b15sf70788eek.11 for ; Tue, 04 Jun 2013 17:17:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:mime-version:in-reply-to:references:date:message-id :subject:from:to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=zQSIMDXAm3hVfhA5JTDuR0A3s/cREf0rOBPKod7bEAM=; b=LRRFeoH5iMJTNg2+LmlUusppFln9QG4WN6w89EjvdeHnMXKvDaeO3ZF9jauO3WwN5/ s1Lm43ukLmaWn/nDwvWLb/NX5agptdwJeMuJwZmYI5Gtxy4aoEwHCWCHCCGV5f+edRyy b8Pucf2Z+4dDuZtvayxwA86k4BSzLt1+Cn3MQK331Npv5lyf/qe2q8E+u3lLIop9OUQ2 L1hPEKdXNSYUfXymiCCaz5tW/IHl9k4XPh5hEOBldELkQCLvJdaPOJ6zjF+jU7dTtaDE pB1+CCzoki+5sOIfunF9cAECZV0VBcET+UVNK4/Qctlp4lkR0D51wBb3J2rjv2JS/F8F IEwA== X-Received: by 10.112.161.6 with SMTP id xo6mr2211278lbb.11.1370391429080; Tue, 04 Jun 2013 17:17:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.18.134 with SMTP id w6ls33299lad.45.gmail; Tue, 04 Jun 2013 17:17:07 -0700 (PDT) X-Received: by 10.112.218.39 with SMTP id pd7mr13912127lbc.13.1370391427846; Tue, 04 Jun 2013 17:17:07 -0700 (PDT) Original-Received: from mail-la0-x22a.google.com (mail-la0-x22a.google.com [2a00:1450:4010:c03::22a]) by mx.google.com with ESMTPS id wc8si18739496lbb.67.2013.06.04.17.17.06 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Jun 2013 17:17:06 -0700 (PDT) Received-SPF: pass (google.com: domain of lichray@gmail.com designates 2a00:1450:4010:c03::22a as permitted sender) client-ip=2a00:1450:4010:c03::22a; Original-Received: by mail-la0-f42.google.com with SMTP id eb20so863351lab.1 for ; Tue, 04 Jun 2013 17:17:06 -0700 (PDT) X-Received: by 10.112.199.98 with SMTP id jj2mr14277814lbc.114.1370391426674; Tue, 04 Jun 2013 17:17:06 -0700 (PDT) Original-Received: by 10.112.146.99 with HTTP; Tue, 4 Jun 2013 17:17:06 -0700 (PDT) In-Reply-To: X-Original-Sender: lichray@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of lichray@gmail.com designates 2a00:1450:4010:c03::22a as permitted sender) smtp.mail=lichray@gmail.com; dkim=pass header.i=@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:4868 Archived-At: On Tue, Jun 4, 2013 at 7:26 PM, Jeffrey Yasskin wrote: > const array_ref carr2 = ...; > do_stuff_with(carr2); > use(carr2.size()); > > the compiler _can_ assume carr.size() is the same. In a general case, since the same memory can be referred by another pointer or reference, optimizers just won't analysis the data flow. Instead, they know many thing about the control flow. If the above code is optimized, that means you don't have the code to change the size; it doesn't matter you declare it as const or not. -- Zhihao Yuan, ID lichray The best way to predict the future is to invent it. ___________________________________________________ 4BSD -- http://4bsd.biz/ -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/?hl=en. .