220 37085 <805d3933-0cf9-465f-906c-849ab25c7a63@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: bastienpenava@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: specify concept implementation Date: Mon, 26 Feb 2018 11:48:16 -0800 (PST) Lines: 127 Approved: news@gmane.org Message-ID: <805d3933-0cf9-465f-906c-849ab25c7a63@isocpp.org> References: <93e7e509-edf0-4df6-9b2f-555bba92a04a@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_15043_70308916.1519674496113" X-Trace: blaine.gmane.org 1519674377 18385 195.159.176.226 (26 Feb 2018 19:46:17 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 26 Feb 2018 19:46:17 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCG3XHNI6IDRBAOJ2HKAKGQE7DK3YCI@isocpp.org Mon Feb 26 20:46:13 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f199.google.com ([209.85.217.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eqOix-0004FB-Qq for gclcip-std-proposals@m.gmane.org; Mon, 26 Feb 2018 20:46:12 +0100 Original-Received: by mail-ua0-f199.google.com with SMTP id y43sf10490999uac.16 for ; Mon, 26 Feb 2018 11:48:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=9gBcHcIfacRqBje1brujpJbGCUuexRcqh/bvYLU9S4Y=; b=dggx7bK0cMIEcRhjNDeIfU3aXkgwDYI+p1JZSLyPuIQ+/UiNvFkTYLwq4h0H+n34a3 Kkr+ryjtl3rz61sAy0qI+84r2lzgTyWgJlJfIzne3JcGcMGuMWH2xKGH+4XDUnGIqD7R 02Cu6ZrKf6/KMIo2IADP0j1JYTk27yWhwdSNkP4ycVP3ETq+Tg/C4FR5CcQEySgv/RJI Vd/T4bhInzH+cA0KQi1y/Lqcq3smV/vTw9PoyWT/yxOSivT1DM+KxEKpIOj2TByVyLKi z/U0HK7SYjFvmk1fnMP60AnRtzyXGqscL9jCSu2QVRM3w+hBNwh/FGzMwM7TLD1YcQWk tjKg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=9gBcHcIfacRqBje1brujpJbGCUuexRcqh/bvYLU9S4Y=; b=odD071OG51lgNHM/WPqkfFukgQZ6JS+24dVzFVTDCQpCtnt0JnhuFI5QxoInxWMV+e psQF/04Egyr/7tXNab7vnU+psytYkGFJLHopo8OGf+Y96EJpWZH1D9F/eEbcBuPxDyN1 Y7ku/JwPDMPXWS0SnqQwf4etLH9IFzqB3eu/ys9jsLnqZKEz/JCrVzlwcsM5hMUoSVLy ddHg97r6k58DLJiMpV0aSJaWWXj6MUJhmBJPOeUk54HDJg4iyF4K1dXTUwKHLKJ6rZlX uhMJcoXKu0n+GoSxF4Yyj2YrE88USSfjKEaC33HvV8yx60DNh6qxNxmXRy6az76n7SK0 NZPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=9gBcHcIfacRqBje1brujpJbGCUuexRcqh/bvYLU9S4Y=; b=Dr3sQkusbFGtZytV2tciWKYm9IMhDK61w44SQsf68qI6O7xewlYCCI7sV+zQgTVyzc f+rfkhevBIaTpFmj0ViCTyZQskIhDtKszP9HzxxqRCsavjgcI/I+lRbrSCwjUzjP0wmR J0WHR4kwOWSuy7wHhSovAyTQo26gLhmQ9vCqzB/5ODGUZFTiTNt8SotgEsNbeYhFgr9z 6KAzTtR+rcFy/Ml5xTTc/rqgIdW9Bnkn5jRsYA+5mwICV0vBq69JtzpwLRkOtMTvOn+t j7rAFRWfigMldOmwBQDrdfxbQBz3/wa2JRZ4vpTJ/iEXVMmnF97YPDTj9hLTbPWc2hPf VHKA== X-Gm-Message-State: APf1xPAnjRNQgZDq3PWMgATsKcvka/rNOGzrz5dH6m3zq4ceSaHOnKm9 Y2BNhh03jK7dVXdxipxyw7CV2w== X-Google-Smtp-Source: AG47ELsH39q9bBUElgfvrr0Bvask0bTbLJrMnHc8qxgjktVWKI+VAP3YmB26BylZs8ymMH2/HehEIQ== X-Received: by 10.31.107.20 with SMTP id g20mr5955891vkc.0.1519674498164; Mon, 26 Feb 2018 11:48:18 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.185.202 with SMTP id j193ls2950340vkf.18.gmail; Mon, 26 Feb 2018 11:48:16 -0800 (PST) X-Received: by 10.31.162.130 with SMTP id l124mr120346vke.0.1519674496680; Mon, 26 Feb 2018 11:48:16 -0800 (PST) In-Reply-To: X-Original-Sender: BastienPenava@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:37085 Archived-At: ------=_Part_15043_70308916.1519674496113 Content-Type: multipart/alternative; boundary="----=_Part_15044_1523856259.1519674496113" ------=_Part_15044_1523856259.1519674496113 Content-Type: text/plain; charset="UTF-8" On Monday, February 26, 2018 at 5:37:43 PM UTC+1, Nicol Bolas wrote: > > And what about if you want to implement a type that follows a concept, but > you're using non-member functions to implement certain aspects of that > concept? This wouldn't work, would it? > > It's better to just use the obvious tool: `static_assert`. We don't need > to add a whole language feature for trivial convenience like this. > For the non-member function yes it would work as long as you friend-prototype/define said function. 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 The focus point though wasn't the static_assert part at all. It was to explicitly state that a class is meant as an implementation of some concepts for readability purposes and to have some, possibly, interesting debugging side-effects coming from that. I agree though that a whole language feature would be overkill. What about an attribute? template concept ValueType = requires() { T::value; } [[concept C]] //can, or not, check if A satisfies C and issue either a warning or error. struct A { }; -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/805d3933-0cf9-465f-906c-849ab25c7a63%40isocpp.org. ------=_Part_15044_1523856259.1519674496113 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Monday, February 26, 2018 at 5:37:43 PM UTC+1, Nicol Bo= las wrote:
And what about if you want to implement a type that follows a concept, bu= t you're using non-member functions to implement certain aspects of tha= t concept? This wouldn't work, would it?

It's better to just= use the obvious tool: `static_assert`. We don't need to add a whole la= nguage feature for trivial convenience like this.
For the non-member function yes it would work as long as you friend= -prototype/define said function.

As for static_ass= ert, no it's not.
static_assert on an explicit concept ca= ll only triggers a "something went wrong" level of informations:= =C2=A0https://godbolt.org/g/5Hb7zP=

The focus point though wasn't the static_= assert part at all.
It was to explicitly state that a class is me= ant as an implementation of some concepts for readability purposes
and to have some, possibly, interesting debugging side-effects coming fro= m that.=C2=A0

I agree though that a whole lang= uage feature would be overkill.
What about an attribute?

template<cla= ss T>
concept ValueType =3D requires() = { T= ::value; }

[[concept C]= ] <= span style=3D"color: #800;" class=3D"styled-by-prettify">//can, or not, che= ck if A satisfies C and issue either a warning or error.
struct A
{
};

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/805d3933-0cf9-465f-906c-849ab25c7a63= %40isocpp.org.
------=_Part_15044_1523856259.1519674496113-- ------=_Part_15043_70308916.1519674496113-- .