220 2927 <51212821.6040507@bubblescope.net> article Path: news.gmane.org!not-for-mail From: Chris Jefferson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::optional -- request for feedback on the wording Date: Sun, 17 Feb 2013 18:57:37 +0000 Lines: 32 Approved: news@gmane.org Message-ID: <51212821.6040507@bubblescope.net> References: <511FFA5B.7050204@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed X-Trace: ger.gmane.org 1361127462 26894 80.91.229.3 (17 Feb 2013 18:57:42 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 17 Feb 2013 18:57:42 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCF5NPH6QMFRBJOQQSEQKGQE7DVKJ5A@isocpp.org Sun Feb 17 19:58:04 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 1U79R3-0000Dg-Uc for gclcip-std-proposals@m.gmane.org; Sun, 17 Feb 2013 19:58:02 +0100 Original-Received: by mail-ee0-f72.google.com with SMTP id b15sf6402294eek.7 for ; Sun, 17 Feb 2013 10:57:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:x-beenthere:x-received:x-received:received-spf :x-received:message-id:date:from:user-agent:mime-version:to:subject :references:in-reply-to:x-gm-message-state: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=Pe0TOCVPWlq40ZnPOq4QDDZGi5+yXiRhzJrTbalVzlU=; b=mhB8rd9tIj2yvxION9SdXPFfRUU+EckEpRhmiM7beoQ51PY1LSxYoER0vQCtWk2q8e YfoLgBSZD/TP5/3nQtEku26O++09BVLH2LWZ2S84gknW/tCuFrAYHv4a/k52SItOxMQO Nf/3+FIZyhrUNG+nv3NdjTIDbx4GbAaSGUSwvipMRiLI/RpD+aTrerqKu4pj4Nn9jSxT yrKNyl816Esdx/9yJQYjQlY1EFJWFIquvEEvyu3PUibgmJB6KOS/LjW6FRTbMsgHwbDT F1HIzgr3w X-Received: by 10.180.19.132 with SMTP id f4mr2136053wie.2.1361127461976; Sun, 17 Feb 2013 10:57:41 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.101.132 with SMTP id fg4ls398451wib.8.gmail; Sun, 17 Feb 2013 10:57:41 -0800 (PST) X-Received: by 10.194.109.102 with SMTP id hr6mr14790877wjb.24.1361127461071; Sun, 17 Feb 2013 10:57:41 -0800 (PST) X-Received: by 10.194.109.102 with SMTP id hr6mr14790875wjb.24.1361127461060; Sun, 17 Feb 2013 10:57:41 -0800 (PST) Original-Received: from mail-we0-x230.google.com ([2a00:1450:400c:c03::230]) by mx.google.com with ESMTPS id d6si21496485wjw.94.2013.02.17.10.57.40 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 17 Feb 2013 10:57:40 -0800 (PST) Received-SPF: neutral (google.com: 2a00:1450:400c:c03::230 is neither permitted nor denied by best guess record for domain of chris@bubblescope.net) client-ip=2a00:1450:400c:c03::230; Original-Received: by mail-we0-f176.google.com with SMTP id s43so4089923wey.7 for ; Sun, 17 Feb 2013 10:57:40 -0800 (PST) X-Received: by 10.181.12.103 with SMTP id ep7mr16173737wid.12.1361127460574; Sun, 17 Feb 2013 10:57:40 -0800 (PST) Original-Received: from [192.168.1.183] (94-192-86-137.zone6.bethere.co.uk. [94.192.86.137]) by mx.google.com with ESMTPS id bg5sm17460095wib.8.2013.02.17.10.57.38 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 17 Feb 2013 10:57:39 -0800 (PST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 In-Reply-To: X-Gm-Message-State: ALoCoQkKFs36rgXWuKBeVTPaFB7vCMzJYPnjSeZ+I5uvbnhYBoIR4ZqA27AqyBgkXlHv0nPKkAEY X-Original-Sender: chris@bubblescope.net X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 2a00:1450:400c:c03::230 is neither permitted nor denied by best guess record for domain of chris@bubblescope.net) smtp.mail=chris@bubblescope.net 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:2927 Archived-At: On 17/02/13 18:34, Tony V E wrote: > On Sat, Feb 16, 2013 at 4:30 PM, Vicente J. Botet Escriba > wrote: >> >> * optional::optional(const optional& rhs); >> >> What about adding a post-condition on the copied value >> false == bool(rhs) || rhs.value() == this->value() >> > You can't guarantee rhs.value() == this->value() for all T. You are > probably assuming T is Regular. In these kinds of situations I find it helpful to look at other parts of the standard, for example pair assignment says "effects: Initializes members from the corresponding members of the argument". So don't worry about getting 'code equivalent', in situations like this it is fairly obvious what the constructor is supposed to do, so a text description is (my opinion) more than sufficient. Chris -- --- 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. 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