220 39050 article Path: news.gmane.org!.POSTED!not-for-mail From: Richard Hodges Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: constexpr! or constexpr(true) Date: Tue, 10 Jul 2018 09:06:30 +0200 Lines: 199 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="000000000000a32dcb05709fc596" X-Trace: blaine.gmane.org 1531206277 16022 195.159.176.226 (10 Jul 2018 07:04:37 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 10 Jul 2018 07:04:37 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD4PBM7UWAHRBAVWSHNAKGQERGORHFQ@isocpp.org Tue Jul 10 09:04:33 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-io0-f197.google.com ([209.85.223.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fcmhM-000450-B2 for gclcip-std-proposals@m.gmane.org; Tue, 10 Jul 2018 09:04:32 +0200 Original-Received: by mail-io0-f197.google.com with SMTP id t23-v6sf18611381ioa.9 for ; Tue, 10 Jul 2018 00:06:43 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1531206403; cv=pass; d=google.com; s=arc-20160816; b=TCJ7fB9Zu4dVMGkqB1EpfmDD68rukKjVqtK9WmBmhshIj8qywECXfU3/QGQytgvtJb toFDAtJxZWkGdDj0f7IMm8AgDtOeaIxmMRk34wKtNjxMcCx4S3Tqn7m7eExrOlC9YydW bYSVCW8uYQrQC4u6gH0adu9DqPDgm+hFT0BUB5iMCCH9TXe+nOIelqOmkEUsjLsMUbEG g/cZgTD4dot4mCZxmI1yCGrhqMFfi1F7P3f2FusfD25+YmcnYOVbcQBTaB4DjfmevI2v +0ByFl6j8qTq57T3ChiSr5SOzYp2YwXVc1zeyODdyG13OACzmMVGqDqVwlTrPV9aH6PV ll7A== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:to:subject:message-id:date :from:in-reply-to:references:mime-version:arc-authentication-results :arc-message-signature:dkim-signature:arc-authentication-results; bh=WI4HivGObErvRa8J5qjt+FxFsHXo5qngIlo4ccw5W4o=; b=nmKGDmKTbrPH64Wqn4ZaZ/4xlMzZvzS6/vwpHOraFr4zjZG23B8E8C7n9OrTqYkPvM clgq4ltuiHCbyljHq7OTUCYs6T5iIuKjlV22hUulqfRgz3bQjSWtswUztuQoAweyDMXF FyN0qCqxS9xmBKhEvh5VzJqC8LDCExf/4VOQpFxUT+svCE9THm9AjZCQflE+I1ui3NVe EBCnjL7bhejV34vdfUC1IhgyxZZxacZKWrbaDuSqKLgYQzHce7CDlS9v36xhFn/DZhwZ kmVUpQPc8eKUsgt+H01KrfwuQTB08Rb9CkZvQqd1jo6jdCwGyquYgrKkFzNcFHTsWyNP kh6A== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=APXBhk6Y; spf=pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hodges.r@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject: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; bh=WI4HivGObErvRa8J5qjt+FxFsHXo5qngIlo4ccw5W4o=; b=hVqu3sbgNWkcmrO4Uy6sAZT9MeCmbwJSfGVGwUV2PGEFMqK4HHxl9JprPkxCge991B tS5YLKs0fYMuYQIfPxaNvPjs4BTUgFE/fEqhwryqg3SrhX3Ptt1fUAOJGnNzTQc9IXiE 6vd7DBql9lMzw1EGjiMyn3v3wIq8+HhUaNthZRPSWEfS6BJe1S2ZPcK3HjVUJvGBAh4n hmbbQ4FqXskZ+fV7IzR09dT9ZRcBkpzphrzK+P4723YI4IobunofRAUrnoSq2UtwJVTO UHHANkfcSN0jJPN/0wxZPc6enBQ6DVIHcgdSu/fEuiymZO4aCUH7CmTBwrq/lB1Jz3rE eNKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=WI4HivGObErvRa8J5qjt+FxFsHXo5qngIlo4ccw5W4o=; b=CCm1xXFvfOBq85VVY4IhxOu2+JTrNrXvijI4jLvslq5uQtxJEy80FwXYjWZaW9bc0x esCR+LjY67vvK0udNz+adpkwYwnHUmBDIDWh147YX84iWuaQgHbW7/hIWpHEJUnXMaVF MGT+KsvrPjwOMfDfLjcRTscKPqQ18t+K1yjM1iWpS1XU2wpuOHaytoE6TTnLg/8nyoOy Z3fa8f1t/A1nCjs6k3pucjbszCLRZKuuTy5wkJcOg/GHoqqPrHBcaHYnxiYbbKtUWqQA +/Mpnj2esRD0wGTE2ygi0ECc4E1wNM541FYLiJc5PL3VjUcCcUEba3sfC6kbTADoiR8V bJ8w== X-Gm-Message-State: APt69E1EUvnNOaRshja7QM/h80pxdEqqvkxPxWL78tLkMZj7NPM7YCC7 JU4RDl4uvCvFifvtfIpalEd0gA== X-Google-Smtp-Source: AAOMgpeBMKPRyOR67dPiuP/eXT8p9H6CA1mPD/8egnEfRdUY/q6QUDpuxBpOQHHoY/7gzb5WJmoa+A== X-Received: by 2002:a02:b5d1:: with SMTP id y17-v6mr3182620jaj.4.1531206403067; Tue, 10 Jul 2018 00:06:43 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a24:1a82:: with SMTP id 124-v6ls2304570iti.9.gmail; Tue, 10 Jul 2018 00:06:42 -0700 (PDT) X-Received: by 2002:a24:70b:: with SMTP id f11-v6mr19104726itf.137.1531206402012; Tue, 10 Jul 2018 00:06:42 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1531206401; cv=none; d=google.com; s=arc-20160816; b=zvvLZeoRYZ4c5gc3M0TPtqnSrdyZBN6EqZcYcQfJzEupBRXQKPltyH2FRUugu6y05r SyFdo9gkmr7lehslczad81xGENlQbqOw6PbNtOM8h06LoyVMZT4P6kHZ1+sBfNckdxVG gXlx7aSR8kR/g3bAfe8Dt7Y+LsjgKoGm/GXEPbLjsjp7qC64o1UwbK9otOC3OKdWXs6k BrwYzzgMx7hn06Ld8kSdB+bchO6I3TlSmmGebT49Wdf8tnkZuGdb4vOyE6plVVm+9TjE KvbynLbj6E2hh35TLvkrI6+5IfAOsppueLsIOyVebfsuIMif4VTkO6y8xag+k11QmHhJ Istw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:subject:message-id:date:from:in-reply-to:references:mime-version :dkim-signature:arc-authentication-results; bh=RX0ER6pADA6Qef6a1MP1ZbkSlQ0fODfxXzMG8Tzbsgs=; b=boSoa1xzKLQniz+0h+1wUSvevueSvoh+5NQ17sxs/21yOtFRRxhX+9+0dURZRNINYS pnn08STyw58PEvoHJlSXk9yJ0nXzqJEzCqPbB1e3jcAYGxxM09B0YcXTePRC9h7uw0Nb fxt/PSPmpTxMhIqKnU8yP7c3cRdRZCja6WAItrXNFQfpQZadUiq1eA6aqiME9Pe789lu oFkgNbtMhsbH+CL7Xf28H7e0moCRmknvwYeOnnZgptRvTPTk1XX3CrTkDGpRyHh93mxn peqv7JPD1Q9hMu49TqbJXBmNP56w+azFy1i+XNYUKKmF9z+pKXOcaBPR8fj4oI4CQa49 pPZg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=APXBhk6Y; spf=pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hodges.r@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Original-Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id z145-v6sor6142783itc.92.2018.07.10.00.06.41 for (Google Transport Security); Tue, 10 Jul 2018 00:06:41 -0700 (PDT) Received-SPF: pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a24:c2c2:: with SMTP id i185-v6mr3036123itg.76.1531206401468; Tue, 10 Jul 2018 00:06:41 -0700 (PDT) In-Reply-To: X-Original-Sender: hodges.r@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=APXBhk6Y; spf=pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hodges.r@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:39050 Archived-At: --000000000000a32dcb05709fc596 Content-Type: text/plain; charset="UTF-8" On Tue, 10 Jul 2018 at 02:04, wrote: > Hello everyone > > Have the authors of p10731r.html considered if this suggestion: > > constexpr(true) int sqr(int n) { > return n*n; > } > > is preferable and more consistent or flexible than this which they > currently propose: > > constexpr! int sqr(int n) { > return n*n; > } > > And would it offer the following possibility and would it be useful?: > > constexpr(some_condition()) int sqr(int n) { // constexpr this function on > certain conditions. > return n*n; > } > > Also many compilers support forceinline functionality etc. Perhaps this > should be standardized too now? > Therefore I think the authors might want to propose this too: > > inline(false) int sqr(int n) { // force inline. Or inline! if the > committee thinks best. > return n*n; > } > > Which might similarly allow this?: > inline(some_other_condiition()) int sqr(int n) { // force inline. Or > inline! if the committee thinks best. > return n*n; > } > > where some_other_condition might test for a certain platform or compile > where forcing inline or not might be desirable despite what the compiler > thinks. > > It seems to me using ! is a little unusual syntax and be less consistent > and flexible than what I'm proposing but I admit ! is shorter. > > I see such macros regarding forceinline in various code bases such as > libcxx's __config file. So perhaps forceinline's time has come too. > > What do the authors of p1073r1 and others think? > What one of the others thinks: a) The exclamation mark on the end is revolting, adding nothing to the syntax. b) Do you have a compelling, motivating use case in mind? By this I mean a real one, not just "we ought to have it because it seems consistent". I ask for b) because I am strongly of the view that code should express intent, which the compiler then turns into action. What is the "intent" of writing: constexpr(some_test()) int sqr(int n); ? What could some_test() possibly be testing? Why would it matter? The implementation of sqr is either a constexpr expression or it's not. If it is, its constexpr-ness can be undone by the context of its use (because it takes an argument). What's wrong with that? > > Thanks > Show trimmed content > Click here to Reply > > -- > 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/f377a21c-926e-4cd8-9c25-5c36b7a7a62c%40isocpp.org > > . > -- 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/CALvx3hZ8bNfWMYvzty1Dzh6OXs029k5t-nr1m1nP9uCgisA21Q%40mail.gmail.com. --000000000000a32dcb05709fc596 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Tue= , 10 Jul 2018 at 02:04, <gmisocpp@= gmail.com> wrote:
Hello ever= yone

Have the authors of=C2=A0p10731r.html considered if this= suggestion:

constexpr(true) int sqr(int n) {
=C2= =A0 return n*n;
}


is preferable and more consiste= nt or flexible than this which=C2=A0they currently propose:

<= /div>
constexpr! int sqr(int n) {
=C2=A0 return n*n;
}
=
And would=C2=A0it offer=C2=A0the following=C2=A0possibility = and would it be useful?:

constexpr(some_condition(= )) int sqr(int n) { //=C2=A0constexpr this function=C2=A0on certain=C2=A0co= nditions.
=C2=A0 return n*n;
}

Also=C2=A0many compilers= support=C2=A0forceinline functionality etc. Perhaps this should be standar= dized too now?
Therefore I think the authors might want to=C2=A0p= ropose this too:

inline(false) int sqr(int n) { //= force inline. Or inline! if the committee thinks best.
=C2=A0 return n*= n;
}

Which might similarly allow this?:
inline(some_other_condiition()) int sqr(int n) { // force inline. Or inl= ine! if the committee thinks best.
=C2=A0 return n*n;
}
where some_other_condition might=C2=A0test for a certain platfo= rm or compile where forcing inline or not might be desirable despite what t= he compiler thinks.

It seems to me using ! is a li= ttle unusual syntax=C2=A0and be less consistent and flexible than what I= 9;m proposing but=C2=A0I admit ! is shorter.

= I see such macros regarding forceinline in various code bases such as libcx= x's __config file. So perhaps forceinline's time has come too.

What do the authors of=C2=A0p1073r1 and others t= hink?

What one of t= he others thinks:

a) The exclamation mark on the e= nd is revolting, adding nothing to the syntax.

b) = Do you have a compelling, motivating use case in mind? By this I mean a rea= l one, not just "we ought to have it because it seems consistent"= ..

I ask for b) because I am strongly of the view t= hat code should express intent, which the compiler then turns into action. = What is the "intent" of writing:

constexpr(some_test()) int sqr(int n);= =C2=A0

?

What could some_= test() possibly be testing? Why would it matter? The implementation of sqr = is either a constexpr expression or it's not. If it is, its constexpr-n= ess can be undone by the context of its use (because it takes an argument).= What's wrong with that?

=C2=A0
=C2= =A0

Thanks
=
S= how trimmed content
Click here to Reply

--
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-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/f377a21c-926e-= 4cd8-9c25-5c36b7a7a62c%40isocpp.org.

--
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 htt= ps://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CALvx3hZ8bNfWMYvz= ty1Dzh6OXs029k5t-nr1m1nP9uCgisA21Q%40mail.gmail.com.
--000000000000a32dcb05709fc596-- .