220 34696 <79697376-5ccd-470a-b197-ab717ae1d64a@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Niall Douglas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Constexpr maths functions Date: Sat, 7 Oct 2017 16:01:54 -0700 (PDT) Lines: 84 Approved: news@gmane.org Message-ID: <79697376-5ccd-470a-b197-ab717ae1d64a@isocpp.org> References: <01e6fcdd-3250-4017-b53a-cea48f869817@isocpp.org> <8c572022-0abd-6677-4b50-788651354e1e@westcontrol.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_3657_537714681.1507417314853" X-Trace: blaine.gmane.org 1507417314 32158 195.159.176.226 (7 Oct 2017 23:01:54 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 7 Oct 2017 23:01:54 +0000 (UTC) Cc: nialldouglas14@gmail.com, david@westcontrol.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDGKFT5YZADRBY5Z4XHAKGQEW5NZTYY@isocpp.org Sun Oct 08 01:01:49 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f69.google.com ([209.85.213.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e0y6P-0007f1-0J for gclcip-std-proposals@m.gmane.org; Sun, 08 Oct 2017 01:01:49 +0200 Original-Received: by mail-vk0-f69.google.com with SMTP id j189sf12250821vka.13 for ; Sat, 07 Oct 2017 16:01:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc: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=U6fypnF6dXZ2H8Fk/HYplsIksZ1cKmxuR+bQMbmcFiw=; b=axWaUJtjslvx/TRl5rSbN/dUUH+1zrIn+CMx9t5pG03nIsLfyMD8q739bBWDPBkt66 eSipZF8y0mU9dngDUfLI5y5A0OQxQQJ8nplywkDV92Azlqq/v/OGtpRu1GH9MHIFOf2f q/5IdQG1JzXPaEi3tU1kWxYVFZSPFpr4/tNxiNs+nJ1Lcx5lcq6R+BxyagHXpH2xQ1Dl VHJ7VvXjbUL/EmMnUj8dwnWcz6W2PBF3zOLLGGJBvy59+8WDvwA8zUjw5gMgI+1odg1z QQea/6aEwYPHEQlM4UP7Ly3H2kTzUaHWGbIOVrOM5s9QO7uAAjaIH+3h63YppZ3BUqCr Xy1w== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc: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=U6fypnF6dXZ2H8Fk/HYplsIksZ1cKmxuR+bQMbmcFiw=; b=J0IYTcXYHUCHj2PkE5engN83U9WT8n3yafMiC2ciTZfCwi0nE9K1PHf3Yw53wRSRff O1zJtmZnndx1E6FaExfnYEwvnL8FkawSwmiLA+8n2M6ihjCHqiDb8olfbIC8HiBly+c8 osmztjwtnMW37/Bb0VEv4RdSdpp0bW6vzB7BPJlVzzcpjwELrPVVGDrmMZDgVG7n9+5x rzOQSVrKpfuYG399ixkWUt37RJXvhJWlrRkVgyj3PiceSXrtAkdJCI2V/EUYKNmJMzh7 7mSGXLnwbvn1nW+UloyDZy8raIwX4UILmS98mt+2SEArQQ4sBfpwEKMREDZBECV773Ox 9Lmg== 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:cc: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=U6fypnF6dXZ2H8Fk/HYplsIksZ1cKmxuR+bQMbmcFiw=; b=DZSfF/CK21VpSCKmveSs+LUlFHtXK1KQsmAILc9WlKAksKPDfdx9U2B9oQMRKUV6MQ TZEM2sAhtGonWSfmfGNzqg7GkmjvqhfM+i0V8Z+L7Ey0zzMYkz33gezSuHt4mBYFRwCS vi3VPNVeovmh+a7zizfafLIvlYsQJzwaDHLBhoJvDLSqyPC/aweq9Bv11YzjzhK+XowK I38VquZ8K+lh+Lpjy2RM24uOXxPTD5YtAH1qH3Xs4M47mbmxIlVqZbMJi4kNRAhqrSAX HCsZ8wrz3mu48t9sqJ3inmqGr+s9Hn7RD55LXXRzftBaAwazWhXU7Bvg+oWvg4uu17Vm uViw== X-Gm-Message-State: AMCzsaXVeDQe5GN5ugIh0P7wLWOcPDeb0JVG3YiY+OBNFI7DdWHg42xi rBc9iyOjLe1Ff6Y3FIxC/wnc4g== X-Google-Smtp-Source: AOwi7QD2mr2zwQCTb/zUH1kMQnk9wGACwIJOKTF2mPHZvgQB0W8kIWVCwu8nd0RNEpPvCeMQ3wfKkw== X-Received: by 10.159.63.193 with SMTP id m1mr1246047uaj.123.1507417316289; Sat, 07 Oct 2017 16:01:56 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.6.199 with SMTP id 190ls337627vkg.16.gmail; Sat, 07 Oct 2017 16:01:55 -0700 (PDT) X-Received: by 10.31.211.195 with SMTP id k186mr270142vkg.9.1507417315347; Sat, 07 Oct 2017 16:01:55 -0700 (PDT) In-Reply-To: <8c572022-0abd-6677-4b50-788651354e1e@westcontrol.com> X-Original-Sender: nialldouglas14@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:34696 Archived-At: ------=_Part_3657_537714681.1507417314853 Content-Type: multipart/alternative; boundary="----=_Part_3658_1234269762.1507417314853" ------=_Part_3658_1234269762.1507417314853 Content-Type: text/plain; charset="UTF-8" On Saturday, October 7, 2017 at 1:24:46 AM UTC+1, David Brown wrote: > > > On 06/10/17 17:48, Niall Douglas wrote: > > > > Is there any reason why this could not be supported in the C++ > > standards? > > > > Breaks compatibility with C I would imagine. > > > > That would be a reasonable (but not great) justification - though I > don't see how it would. Perhaps errno support would be the problem? > It's not even that. A very common use case for C++ is to compile straight-C programs for the improved optimisation. Thus a C program must run exactly the same in C++ as it would in C. Making the cmath functions go constexpr in C++ breaks that, badly. Niall -- 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/79697376-5ccd-470a-b197-ab717ae1d64a%40isocpp.org. ------=_Part_3658_1234269762.1507417314853 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Saturday, October 7, 2017 at 1:24:46 AM UTC+1, David Br= own wrote:

On 06/10/17 17:48, Niall Douglas wrote:
>=20
> =C2=A0 =C2=A0 Is there any reason why this could not be supported = in the C++
> =C2=A0 =C2=A0 standards?
>=20
> Breaks compatibility with C I would imagine.
>=20

That would be a reasonable (but not great) justification - though I=20
don't see how it would. =C2=A0Perhaps errno support would be the pr= oblem?

It's not even that.

=
A very common use case for C++ is to compile straight-C programs= for the improved optimisation.

Thus a C program m= ust run exactly the same in C++ as it would in C. Making the cmath function= s go constexpr in C++ breaks that, badly.

Niall

--
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/79697376-5ccd-470a-b197-ab717ae1d64a= %40isocpp.org.
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