220 4240 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Fixing Standard Library relational operators (was: Re: optional Rev.4 (N3672): What was the rationale to remove !=, >=, ...) Date: Fri, 3 May 2013 17:43:58 +0300 Lines: 101 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=047d7b2e41a499ac3604dbd16174 X-Trace: ger.gmane.org 1367592245 21577 80.91.229.3 (3 May 2013 14:44:05 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 3 May 2013 14:44:05 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBMM2R6GAKGQER2P5AVI@isocpp.org Fri May 03 16:44:05 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ia0-f200.google.com ([209.85.210.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UYHDP-0002bh-3N for gclcip-std-proposals@m.gmane.org; Fri, 03 May 2013 16:44:03 +0200 Original-Received: by mail-ia0-f200.google.com with SMTP id p22sf6154209iad.3 for ; Fri, 03 May 2013 07:44:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received:received-spf:mime-version :x-received: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=p01kgRyEWal7rxw1RE5JGzn5oJMnU9cdwVQGvfzjfqs=; b=HD5jnpHjyWm30RWf/ICPeXrt7nBLAQHSyoglLRFuMlyTxZkXM/2fuTDyrxmNQhi1Q7 lgCdc17uNGdDCOF+GE7COUx1tBz4LS30lx7qmA2qCBWKSlrMiOzPfMon/FrzquV86j2U OOWv1YTslX001xphk4yMQTnVMi5SYDLVPRtJF4bv76gIQeqrTkYBHkU5TrS/WimjMIfY wbJhzanx/7KLb5qTIVG2sEe3J6L52uP/7ueiwavgpa7J/bllknqrTII1KFJaP9Yz4t6B Qjf+yvmXkDeLMkasfHhgtTX9D4BRemxWyiZAuiRW/ArBlNMeSNrx3TJshZnd7U4sCscK X-Received: by 10.182.61.4 with SMTP id l4mr8958890obr.9.1367592241946; Fri, 03 May 2013 07:44:01 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.118.197 with SMTP id ko5ls212370obb.35.gmail; Fri, 03 May 2013 07:43:59 -0700 (PDT) X-Received: by 10.182.97.40 with SMTP id dx8mr2970894obb.54.1367592239129; Fri, 03 May 2013 07:43:59 -0700 (PDT) Original-Received: from mail-oa0-f51.google.com (mail-oa0-f51.google.com [209.85.219.51]) by mx.google.com with ESMTPS id fx9si2535875obb.153.2013.05.03.07.43.59 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 03 May 2013 07:43:59 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.219.51 as permitted sender) client-ip=209.85.219.51; Original-Received: by mail-oa0-f51.google.com with SMTP id g12so1701303oah.38 for ; Fri, 03 May 2013 07:43:59 -0700 (PDT) X-Received: by 10.182.97.129 with SMTP id ea1mr2985815obb.85.1367592238949; Fri, 03 May 2013 07:43:58 -0700 (PDT) Original-Received: by 10.76.10.130 with HTTP; Fri, 3 May 2013 07:43:58 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.219.51 as permitted sender) smtp.mail=ville.voutilainen@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:4240 Archived-At: --047d7b2e41a499ac3604dbd16174 Content-Type: text/plain; charset=ISO-8859-1 On 3 May 2013 17:27, Nevin Liber wrote: > The other, simpler possibility is to not specialize the arithmetic > operations: > > operator< should be implemented in terms of std::less of the underlying > component(s) > operator== should be implemented in terms of std::equal_to of the > underlying component(s) > I think Tony has a valid point about the first one - it will give a wrapper of a complex an operator<, and potentially for other types of the kind where operator< isn't desirable, but an std::less specialization is. I fail to see what equal_to brings into this, but that's just because I fail to imagine when is it ever not the same as operator==. > This may have surprising results for those who, for instance, think > operator< and std::less should do different things (the only place in the > standard which does this as far as I know is for pointers, and that is only > because C doesn't give them a total ordering), but I see that being as > insane as NaN. > > > Agreed, the pointer situation is unfortunate, but it seems likely that other types will have this difference between op< and less. -- --- 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. --047d7b2e41a499ac3604dbd16174 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable



On 3 May 2013 17:27, Nevin Liber <nevin@eviloverlord.com&= gt; wrote:
The other, simpler possibility is to not spe= cialize the arithmetic operations:

operator< should be implemented in terms of std::less of the underly= ing component(s)
operator=3D=3D should be implemented in terms of std::e= qual_to of the underlying component(s)

I think Tony has a valid point about the first one - it will give a wr= apper of a complex an operator<,
and potentially for other= types of the kind where operator< isn't desirable, but an std::less= specialization
is. I fail to see what equal_to brings into this, but that's just becau= se I fail to imagine when is it
ever not the same as operator=3D=3D. =A0
This may have surprising results for those = who, for instance, think operator< and std::less should do different thi= ngs (the only place in the standard which does this as far as I know is for= pointers, and that is only because C doesn't give them a total orderin= g), but I see that being as insane as NaN.



Agreed, the pointer si= tuation is unfortunate, but it seems likely that other types will have this= difference
between op< and less.

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