220 6154 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: std::degenerate<> class template : primitive/enum types with a special "undefined" value Date: Wed, 4 Sep 2013 19:20:51 +0300 Lines: 109 Approved: news@gmane.org Message-ID: References: <18ab4801-260a-4228-8a7b-a71248b624e2@isocpp.org> <77a1bdf8-1e0d-4294-b528-d08ba5403c98@isocpp.org> <023111c2-c983-407d-918f-39be42aa2949@isocpp.org> <88ef15f1-6942-476e-b26c-6873ef6e6f0b@isocpp.org> <01900060-3aac-4645-a4a8-93b4e8760e42@isocpp.org> <5e63fe81-ab33-4bbb-ab4c-305f8b90140a@isocpp.org> <51a05a5a-ad56-4ffa-81d8-759953a93766@isocpp.org> <787f2f45-1fbc-4ce5-90fc-d8f0d8c2b8f4@isocpp.org> <6da8e8d3-7c26-4841-bc3f-40dd0715e92b@isocpp.org> <5226D6A4.4040707@wanadoo.fr> <90eb2850-ff75-47b6-979d-ac7400146b0b@isocpp.org> <52275A58.502@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=089e0149ce365d134d04e5913017 X-Trace: ger.gmane.org 1378311649 16114 80.91.229.3 (4 Sep 2013 16:20:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 4 Sep 2013 16:20:49 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBY53TWIQKGQEOMEADKA@isocpp.org Wed Sep 04 18:20:53 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f72.google.com ([209.85.219.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VHFp7-0000nQ-3t for gclcip-std-proposals@m.gmane.org; Wed, 04 Sep 2013 18:20:53 +0200 Original-Received: by mail-oa0-f72.google.com with SMTP id i4sf1924213oah.11 for ; Wed, 04 Sep 2013 09:20:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=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:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=rnmeNi4pexYIk/ch5QC/+qDsLU+86CwxWI3dY3e7woo=; b=grUf00w5QS45WIxr2tnxDlr0/gvPG562wQyu8nhmTVpO8c0bdT5idQoaG49I4sOsL9 ftItoCGOtvx4VVr6enPW6yXLZYWRrjwlRwUOBEm1RflKkhk6w34N1VF1ct+F3JaeKOL/ 47/m3UAdQc9LXpfYeLtx4KnNhPa0SG15Disi0nsqc2Ld238DG7DZcORYpIz9I5P9LYvD 25vKCG6am9haqvUFq0zTbX84TnDaR8hGdVsw+MLMmzTHZNkMX684fidJ9c8aH8Dy8E1J agSl5cCGvJQSN4D0L08q7sXiV0nt8S2b2n2n3vnM/tGOy3UPZJ6Bj2qnK3zndrEVNzGz CTvQ== X-Received: by 10.182.205.138 with SMTP id lg10mr658402obc.33.1378311652025; Wed, 04 Sep 2013 09:20:52 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.236.232 with SMTP id ux8ls43164obc.73.gmail; Wed, 04 Sep 2013 09:20:51 -0700 (PDT) X-Received: by 10.182.88.202 with SMTP id bi10mr2757591obb.91.1378311651469; Wed, 04 Sep 2013 09:20:51 -0700 (PDT) Original-Received: from mail-oa0-x236.google.com (mail-oa0-x236.google.com [2607:f8b0:4003:c02::236]) by mx.google.com with ESMTPS id tk5si12643324oeb.145.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 04 Sep 2013 09:20:51 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4003:c02::236 as permitted sender) client-ip=2607:f8b0:4003:c02::236; Original-Received: by mail-oa0-f54.google.com with SMTP id j10so719697oah.27 for ; Wed, 04 Sep 2013 09:20:51 -0700 (PDT) X-Received: by 10.60.45.102 with SMTP id l6mr2778852oem.36.1378311651265; Wed, 04 Sep 2013 09:20:51 -0700 (PDT) Original-Received: by 10.76.176.1 with HTTP; Wed, 4 Sep 2013 09:20:51 -0700 (PDT) In-Reply-To: <52275A58.502@wanadoo.fr> 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 2607:f8b0:4003:c02::236 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) d=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:6154 Archived-At: --089e0149ce365d134d04e5913017 Content-Type: text/plain; charset=ISO-8859-1 On 4 September 2013 19:05, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote: > In this way optional doesn't changes its interface (preserv only one > template parameter), and we are able to have > > >> optional >> >> and >> >> optional> >> > > That seems way too much like a kludge. Sure, you can `template using=` > your way around it, but we shouldn't *have* to do things like that just > to make something useable. What is so wrong with just making `optional Tester>` as a variation? We do something similar for `unique_ptr`. > > There is nothing wrong. Just this must be done quickly as once in C++14 > it would be not so easy to change the std::optional interface. My > suggestion could be adopted just after c++14 is released. > > > Perhaps we should leave optional well alone and consider something like http://rk.hekko.pl/constrained_value/ as a potential solution for cases where you want a type is a constrained value rather than a nullable proxy. -- --- 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/. --089e0149ce365d134d04e5913017 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable



On 4 September 2013 19:05, Vicente J. Botet Escriba <vicent= e.botet@wanadoo.fr> wrote:
=20 =20 =20
In this way optional doesn'= t changes its interface (preserv only one template parameter), and we are able to have

optional<T>

and

optional<degenerate<Player, integral_constant<Player, Player(-1)>>

That seems way too much like a kludge. Sure, you can `template using=3D` your way around it, but we shouldn't have to do things like that just to make something useable. What is so wrong with just making `optional<T, Tester>` as a variation? We do something similar for `unique_ptr`.

There is nothing wrong. Just this must be done quickly as once in C++14 it would be not so easy to change the std::optional interface. My suggestion could be adopted just after c++14 is released.



Perhaps we= should leave optional well alone and consider something like http://rk.hekko.pl/constrained_value/<= /a>
=

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