220 4424 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: Wed, 15 May 2013 11:48:32 +0300 Lines: 140 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=089e01229c308d9e6904dcbdd018 X-Trace: ger.gmane.org 1368607723 26462 80.91.229.3 (15 May 2013 08:48:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 15 May 2013 08:48:43 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBY4XZWGAKGQEBGT4A6A@isocpp.org Wed May 15 10:48:43 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ie0-f197.google.com ([209.85.223.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UcXO0-0002CI-Mm for gclcip-std-proposals@m.gmane.org; Wed, 15 May 2013 10:48:37 +0200 Original-Received: by mail-ie0-f197.google.com with SMTP id 16sf5535691iea.0 for ; Wed, 15 May 2013 01:48:35 -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=paX+gaUckgnlSwpUoCNU1mug5UtKEsnkp2euIYBOfyw=; b=HwLt+Oiut3dVDWD74iCVz+XI0mLBfLBIvBaNxTnKwoFdF3PSgpndhBaY2/LBsJOSdM s7e+KnqIsl9XhNAx3z33Y20Urm/D1IlF9gLfjKMjMvDF61DpFswP9RPzpbzSOO+dVOi2 sws6zVWwRzuf5mRI8OxnNf0BpZ+mEVkaE4Az5V2nlyDiXoTb6bTdJ/avN+MSrxkczRK8 YXAg7a7Q8fRmkDivoztEG8DG930io6r5G+E5t27uXxFvprgBZfph7+wkbb6dwTCEdQeI dEKQ/fG18KPsNjCS+g+ihhuItHXwX7WGv2MFUbALCX9by0ZWuBtC3IA+r/5lD3oebAWe X-Received: by 10.182.120.228 with SMTP id lf4mr10901804obb.20.1368607715513; Wed, 15 May 2013 01:48:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.86.99 with SMTP id o3ls123221obz.97.gmail; Wed, 15 May 2013 01:48:32 -0700 (PDT) X-Received: by 10.182.60.136 with SMTP id h8mr16548351obr.47.1368607712843; Wed, 15 May 2013 01:48:32 -0700 (PDT) Original-Received: from mail-oa0-f52.google.com (mail-oa0-f52.google.com [209.85.219.52]) by mx.google.com with ESMTPS id rm9si1108654oeb.2.2013.05.15.01.48.32 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 15 May 2013 01:48:32 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.219.52 as permitted sender) client-ip=209.85.219.52; Original-Received: by mail-oa0-f52.google.com with SMTP id h1so1865368oag.11 for ; Wed, 15 May 2013 01:48:32 -0700 (PDT) X-Received: by 10.60.33.105 with SMTP id q9mr18511598oei.54.1368607712712; Wed, 15 May 2013 01:48:32 -0700 (PDT) Original-Received: by 10.76.10.130 with HTTP; Wed, 15 May 2013 01:48:32 -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 209.85.219.52 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:4424 Archived-At: --089e01229c308d9e6904dcbdd018 Content-Type: text/plain; charset=ISO-8859-1 On 8 May 2013 01:29, Fernando Cacciola wrote: > On Tue, May 7, 2013 at 7:14 PM, Lawrence Crowl wrote: > >> >> The naming is unfortunate, but the distinction between value ordering >> and representation ordering is fundamental and deserves explicit >> recognition in the language. Right now, we have the convention that >> value ordering is spelled operator< and representation ordering is >> spelled std::less. >> >> Well, I was not aware that this was, or is, the intention, but I do agree > with the distinction between the two types of orderings, specially in the > case where there is no value ordering at all, but there (always) is some > valid representation ordering for the sake of lookups. I often resort to > constructing a (large enough) integer out of the bits of all fields just > for that. > > I also very much like the idea of using < and std::less for one and the > other. > > I also agree that, for the sake of associative lookup, defininng > std::greater in terms of std::less is exactly right, regardless of how > operator > would be defined (so I'm saying I've got it wrong all along > thinking that > in terms of < is a good idea because that's how the std > functors work) > > Having said all that, I now feel that the appropriate resolution for > std::optional<> is to implement all operators in terms of the underlying > type. The rest of the library should IMO do the same, but if it can't be > changed, let's at least avoid perpetuating the mistake. > > > I did a little bit of further homework on the matter. boost::tuple does NOT synthesize the comparison operators, but rather calls the operator of the underlying type. The existing practice isn't consistent. ;) This needs at least an overview paper. I'd be willing to entertain the idea to propose making all relational operators, including tuple and containers, to not synthesize. I suppose the fallback plans are synthesize-for-all and deliberately-inconsistent, not necessarily in any preference order. In addition to that, tuples and containers would seemingly need std::less specializations. That's actually somewhat separate. Fernando, Tony, would you be interested in coauthoring? -- --- 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. --089e01229c308d9e6904dcbdd018 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable



On 8 May 2013 01:29, Fernando Cacciola <fernando.cacciol= a@gmail.com> wrote:
=
On Tue, May 7, 2013 at 7:14 PM= , Lawrence Crowl <crowl@googlers.com> wrote:

The naming is unfortunate, but the disti= nction between value ordering
and representation ordering is fundamental and deserves explicit
recognition in the language. =A0Right now, we have the convention that
value ordering is spelled operator< and representation ordering is
spelled std::less.

Well, I was not aware that this was, or is, the= intention, but I do agree with the distinction between the two types of or= derings, specially in the case where there is no value ordering at all, but= there (always) is some valid representation ordering for the sake of looku= ps. I often resort to constructing a (large enough) integer out of the bits= of all fields just for that.

I also very much like the idea of using < and std::less f= or one and the other.

I also agree that, for the sake of = associative lookup, defininng std::greater in terms of std::less is exactly= right, regardless of how operator > would be defined (so I'm saying= I've got it wrong all along thinking that > in terms of < is a g= ood idea because that's how the std functors work)

Having said all that, I now feel that the appropr= iate resolution for std::optional<> is to implement all operators in = terms of the underlying type. The rest of the library should IMO do the sam= e, but if it can't be changed, let's at least avoid perpetuating th= e mistake.



I did a little bit of further homework on the matter. boost::tuple does NO= T synthesize the comparison operators,
but rather calls the operator of = the underlying type. The existing practice isn't consistent. ;)

This needs at least an overview paper. I'd be willing to= entertain the idea to propose making all relational
operators, includin= g tuple and containers, to not synthesize. I suppose the fallback plans are= synthesize-for-all
and deliberately-inconsistent, not necessarily in any preference order.
=
In addition to that, tuples and containers would seemingly = need std::less specializations. That's actually somewhat separate.

Fernando, Tony, would you be intereste= d in coauthoring?

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