220 39520 article Path: news.gmane.org!.POSTED!not-for-mail From: Nicolas Lesser Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: constexpr! or constexpr(true) Date: Fri, 3 Aug 2018 07:47:30 -0700 Lines: 175 Approved: news@gmane.org Message-ID: References: <1c719172-4ea9-4cfc-b491-d1c7da7ccaac@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="000000000000e917ed05728902ad" X-Trace: blaine.gmane.org 1533307549 2781 195.159.176.226 (3 Aug 2018 14:45:49 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 3 Aug 2018 14:45:49 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDXKNLEUTADRBFOWSHNQKGQEOCWPXIY@isocpp.org Fri Aug 03 16:45:45 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f71.google.com ([209.85.218.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1flbKm-0000Zo-05 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id p206-v6sor2678859oif.246.2018.08.03.07.47.49 for (Google Transport Security); Fri, 03 Aug 2018 07:47:49 -0700 (PDT) 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 2002:aca:dbc2:: with SMTP id s185-v6mr3236280oig.251.1533307668468; Fri, 03 Aug 2018 07:47:48 -0700 (PDT) In-Reply-To: <1c719172-4ea9-4cfc-b491-d1c7da7ccaac@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=bUzdyHpT; 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:39520 Archived-At: --000000000000e917ed05728902ad Content-Type: text/plain; charset="UTF-8" Why would one need to have a function that is conditionally constexpr!? On Thu, Aug 2, 2018 at 11:19 PM wrote: > The constexpr will need to go after the parameters, so that it can express > a condition that is dependent on the actual value of the parameters. An > example is to control recursion. Perhaps: > > auto factorial(int n)->int constexpr(n<100) { > if(n==0) return 1; > else return n*factorial(n-1); > } > > On Monday, July 9, 2018 at 8:04:11 PM UTC-4, gmis...@gmail.com 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? >> >> 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/1c719172-4ea9-4cfc-b491-d1c7da7ccaac%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/CALmDwq0skNY43NToFiQwKpvTwUSv0XWuSuRA1yEFq-A5MreK1w%40mail.gmail.com. --000000000000e917ed05728902ad Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Why would one need to have a function that is conditionall= y constexpr!?

On Thu, = Aug 2, 2018 at 11:19 PM <chatham= 130@gmail.com> wrote:
The constexpr will need to go after the parameters, so that it c= an express a condition that is dependent on the actual value of the paramet= ers. An example is to control recursion. Perhaps:

auto f= actorial(int n)->int constexpr(n<100) {
=C2=A0 =C2=A0if(n= =3D=3D0) return 1;
=C2=A0 =C2=A0else return n*factorial(n-1);
= }

On Monday, July 9, 2018 at 8:04:11 PM UTC-4, = gmis...@gmail.com wrote:

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



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()) i= nt sqr(int n) { //=C2=A0constexpr this function=C2=A0on certain=C2=A0condit= ions.
=C2=A0 return n*n;
}

Also=C2=A0many compilers sup= port=C2=A0forceinline functionality etc. Perhaps this should be standardize= d too now?
Therefore I think the authors might want to=C2=A0propo= se this too:

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

Which might similarly allow this?:
i= nline(some_other_condiition()) int sqr(int n) { // force inline. Or inline!= if the committee thinks best.
=C2=A0 return n*n;
}

where some_other_condition might=C2=A0test for a certain platform o= r compile where forcing inline or not might be desirable despite what the c= ompiler thinks.

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

I se= e such macros regarding forceinline in various code bases such as libcxx= 9;s __config file. So perhaps forceinline's time has come too.

What do the authors of=C2=A0p1073r1 and others think= ?

Thanks
Show trimmed content
Click here= to Reply

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