220 37087 article Path: news.gmane.org!.POSTED!not-for-mail From: Nicolas Lesser Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: specify concept implementation Date: Mon, 26 Feb 2018 21:04:28 +0100 Lines: 70 Approved: news@gmane.org Message-ID: References: <93e7e509-edf0-4df6-9b2f-555bba92a04a@isocpp.org> <805d3933-0cf9-465f-906c-849ab25c7a63@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a11482c20774e2705662304f7" X-Trace: blaine.gmane.org 1519675348 15181 195.159.176.226 (26 Feb 2018 20:02:28 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 26 Feb 2018 20:02:28 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDXKNLEUTADRBTOQ2HKAKGQEKOTHAIQ@isocpp.org Mon Feb 26 21:02:24 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ot0-f199.google.com ([74.125.82.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eqOyd-0003Rs-O0 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id b6sor1314500otf.278.2018.02.26.12.04.28 for (Google Transport Security); Mon, 26 Feb 2018 12:04:28 -0800 (PST) Received-SPF: pass (google.com: domain of blitzrakete@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.157.65.187 with SMTP id p56mr8948646ote.123.1519675468368; Mon, 26 Feb 2018 12:04:28 -0800 (PST) Original-Received: by 10.157.94.1 with HTTP; Mon, 26 Feb 2018 12:04:28 -0800 (PST) In-Reply-To: <805d3933-0cf9-465f-906c-849ab25c7a63@isocpp.org> X-Original-Sender: blitzrakete@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=qtsw8nII; spf=pass (google.com: domain of blitzrakete@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=blitzrakete@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com 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:37087 Archived-At: --001a11482c20774e2705662304f7 Content-Type: text/plain; charset="UTF-8" > > As for static_assert, no it's not. > static_assert on an explicit concept call only triggers a "something went > wrong" level of informations: https://godbolt.org/g/5Hb7zP > That's a quality of implementation issue. I fully expect gcc to improve this error message in the future. I agree though that a whole language feature would be overkill. > What about an attribute? > Why not use requires? struct A requires C {}; It looks more like a function constraint and doesn't require any weird language feature. Also, attributes should not change the meaning of the program if they are ignored, so using attributes is a non-starter. -- 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. 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That's a = quality of implementation issue. I fully expect gcc to improve this error m= essage in the future.

I agree though that a whole language feature would be o= verkill.
What about an attribute?
Why not use requires?

struct A requir= es C<A> {};

It looks more like a function co= nstraint and doesn't require any weird language feature. Also, attribut= es should not change the meaning of the program if they are ignored, so usi= ng attributes is a non-starter.

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