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Botet Escriba" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Default swap/hash_value Date: Fri, 15 Jan 2016 21:47:48 +0100 Lines: 41 Approved: news@gmane.org Message-ID: <56995AF4.3050003@wanadoo.fr> References: <569582E5.1040108@wanadoo.fr> <2ca0a385-6399-4ac3-ba0d-609628ea4ec6@isocpp.org> <5697EAD8.8080104@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1452890878 16948 80.91.229.3 (15 Jan 2016 20:47:58 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 15 Jan 2016 20:47:58 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDH67CONY4PBB45V4W2AKGQEPYLPJ2A@isocpp.org Fri Jan 15 21:47:48 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lb0-f199.google.com ([209.85.217.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aKBHg-0005Jz-Pt for gclcip-std-proposals@m.gmane.org; Fri, 15 Jan 2016 21:47:48 +0100 Original-Received: by mail-lb0-f199.google.com with SMTP id ti8sf150664444lbb.2 for ; Fri, 15 Jan 2016 12:47:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-type:content-transfer-encoding :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=mZdNlX5vUTZcPcZmEbpCWXdJ7FYLb7w68A+729M715E=; b=xe8IyS/R+jbbTgyD+2nVMjHFi7DrazprvLVfPNk4qCatnsxjtBit4HjJJCyxiXVfOo +Gis5dLdoSFaaQgTTePC80XWwDpO+qQwDFyi7mHYCdXLM/Uur6xFRUqJkj3DKHzrk7Ws 90e/asFX5yW5PQM1dF4TiWQJhiERrbcClCg6FLpIpOS3pzQgZlEg1K6qbrNqP/RAcUG0 5Q0enrM7MQ8XhNPUQTXQ1gxAhqMXt3wY2nxPfZJuoyQY3AMNbKriPslKJ9H3MqBuC3ED GEOlkfmg2Hqf7kA7KtjYZ29Yi4nEYR/U2vY0O2y2h6qg/04pSUphUMh9ksSvm X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-type :content-transfer-encoding:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=mZdNlX5vUTZcPcZmEbpCWXdJ7FYLb7w68A+729M715E=; b=HFWBCXPZ9iW9eWli6uIXII2Gwc/239FIUxsFDG635U6c0BWfjo424Nkrp1YomrF/ib c5ebU3xszHzsrSghCpE6gsEtYRhQIk0sl5Tux7uWJJEF/I66HaAUVVrRlrHiT7XO//Gx UaxWHTan6OykyPklisgH0uT4I2lBSFRQcEC9zBXUZZyly1yshMnm4nW/5xiiYTQaWyJ9 TGAKyEWYC008+qPFr6SdIaEv7mJo9h6VRKAEXcKtzGc+HJv/gSY+0TVWTwb5SOxDPmWX fi99d9kVYkBfiWw2SE2xEaqfilJkQlZ0U6Ko04UrzB53Ds0 X-Gm-Message-State: AG10YOSPNqMj8d+8Qg6YYk9Ltv13Ghlved3T8E90uvR+LkKxjsKevU5zunIg4J5gt/3i9A== X-Received: by 10.28.172.194 with SMTP id v185mr69428wme.5.1452890868366; Fri, 15 Jan 2016 12:47:48 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.109.143 with SMTP id b15ls201758wmi.28.canary; Fri, 15 Jan 2016 12:47:47 -0800 (PST) X-Received: by 10.194.110.230 with SMTP id id6mr11400980wjb.67.1452890867374; Fri, 15 Jan 2016 12:47:47 -0800 (PST) Original-Received: from smtp.smtpout.orange.fr (smtp05.smtpout.orange.fr. [80.12.242.127]) by mx.google.com with ESMTPS id pd7si19936166wjb.47.2016.01.15.12.47.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 15 Jan 2016 12:47:47 -0800 (PST) Received-SPF: neutral (google.com: 80.12.242.127 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) client-ip=80.12.242.127; Original-Received: from new-host.home ([92.139.160.222]) by mwinf5d28 with ME id 6Lnm1s00N4oBxcU03Lnnvf; Fri, 15 Jan 2016 21:47:47 +0100 X-ME-Helo: new-host.home X-ME-Auth: dmljZW50ZS5ib3RldEB3YW5hZG9vLmZy X-ME-Date: Fri, 15 Jan 2016 21:47:47 +0100 X-ME-IP: 92.139.160.222 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 In-Reply-To: X-Original-Sender: vicente.botet@wanadoo.fr X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 80.12.242.127 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) smtp.mailfrom=vicente.botet@wanadoo.fr Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:23744 Archived-At: Le 14/01/2016 22:02, Tomasz a =C3=A9crit : > I see the reasoning between making the generation of hash_value=20 > depended on the generation of the operator=3D=3D, as we must guarantee=20 > that o1 =3D=3D o2 implies that hash_value(o1) =3D=3D hash_value(o2). Howe= ver I=20 > do not see any correlation between generation of swap and operator=3D=3D.= =20 > If move-constructor can be generated then we will have default=20 > implementation of swap (via std::swap). I think that you should=20 > generate swap for every class that have generated move operations (no=20 > user defined: copy/move constructor, copy/move assignment and destructor)= .. > I believe that you are right, swap has nothing to be with =3D=3D. > I may be beneficial to have proper rule of six: i.e. non of following=20 > copy constructor/assigment, move constructor/assignment, swap,=20 > destructor is generated if at least on of them is defined. However=20 > this would be breaking change (as we may already have classes with=20 > swap, that uses compiler generated special functions), so I would=20 > stick to making swap depended on other five. Agreed. > > Also the dependency on rule of five, would also lead of question if we=20 > should support defining swap on request via =3Ddefault. I'll consider this point. It could be sometimes useful, e.g. when the=20 defined destructor is not managing resources. Thanks for catching this, Vicente --=20 ---=20 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 e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at https://groups.google.com/a/isocpp.org/group/std-propos= als/. .