220 31468 article Path: news.gmane.org!.POSTED!not-for-mail From: Richard Smith Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: overloading by constexpr (round 2?) 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[2a00:1450:400c:c09::22f]) by mx.google.com with ESMTPS id g80si27997835wrd.149.2017.03.06.13.30.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Mar 2017 13:30:31 -0800 (PST) Received-SPF: pass (google.com: domain of metafoo@gmail.com designates 2a00:1450:400c:c09::22f as permitted sender) client-ip=2a00:1450:400c:c09::22f; Original-Received: by mail-wm0-x22f.google.com with SMTP id n11so75939505wma.0 for ; Mon, 06 Mar 2017 13:30:31 -0800 (PST) X-Received: by 10.28.238.140 with SMTP id j12mr14805256wmi.35.1488835830952; Mon, 06 Mar 2017 13:30:30 -0800 (PST) Original-Sender: metafoo@gmail.com Original-Received: by 10.80.148.82 with HTTP; Mon, 6 Mar 2017 13:30:10 -0800 (PST) In-Reply-To: X-Original-Sender: richard@metafoo.co.uk X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of metafoo@gmail.com designates 2a00:1450:400c:c09::22f as permitted sender) smtp.mailfrom=metafoo@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:31468 Archived-At: --001a11471460d53e2e054a169a4c Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable You might want to get in touch with the author of http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0595r0.html (which was discussed in Evolution last week and seems to have had a favourable reception). On 6 March 2017 at 10:15, dgutson . wrote: > I'm proposing the ability to provide two versions of a function, > overloaded by the constexpr specifier: one constexpr version and another > non-constexpr version, and let the compiler use the appropriate one > according to the context. > > A slightly similar subject has been discussed before ( > https://groups.google.com/a/isocpp.org/d/topic/std-proposals/oxijwTY-ft4/ > discussion ). > Additionally, people seems to be interested in detecting constexpr-ness > (e.g. http://stackoverflow.com/questions/15232758/detecting- > constexpr-with-sfinae) to achieve the same "manually". > > I'm talking about to make this simpler: > > constexpr int f() > { > return 1; > } > > int f() > { > return 2; > } > > constexpr auto a =3D f(); // a =3D 1 > auto fun =3D std::function(f); > int b =3D fun(); // b =3D 2 > > If there is some interest, I can star working in a gcc fork as a prototyp= e. > > BRgds, > > Daniel. > > > -- > Who=E2=80=99s got the sweetest disposition? > One guess, that=E2=80=99s who? > Who=E2=80=99d never, ever start an argument? > Who never shows a bit of temperament? > Who's never wrong but always right? > Who'd never dream of starting a fight? > Who get stuck with all the bad luck? > > -- > 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/CAFdMc-2q3KpV% > 2Bm5cfWr6b02XmHVUdxsNCNAVFG%2BmzCv0QY7ZRg%40mail.gmail.com > > . > --=20 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 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/CAOfiQqm4VgaS8OSeopB88dE68CNYRubwZa5H0f2F0rn6FsO= WXw%40mail.gmail.com. --001a11471460d53e2e054a169a4c Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
You = might want to get in touch with the author of http://www.open-std.org= /jtc1/sc22/wg21/docs/papers/2017/p0595r0.html (which was discussed in E= volution last week and seems to have had a favourable reception).

On 6 March 2017= at 10:15, dgutson . <danielgutson@gmail.com> wrote:
I'm proposing the ability to provide two versions of a function,=20 overloaded by the constexpr specifier: one constexpr version and another non-constexpr version, and let the compiler use the appropriate one=20 according to the context.

A slightly similar subjec= t has been discussed before (https:/= /groups.google.com/a/isocpp.org/d/topic/std-proposals/oxijwTY-ft4= /discussion ).
Additionally, people seems to be inte= rested in detecting constexpr-ness (e.g. htt= p://stackoverflow.com/questions/15232758/detecting-constexpr-with= -sfinae) to achieve the same "manually".

I&= #39;m talking about to make this simpler:

constexpr int f= ()
{
=C2=A0=C2=A0=C2=A0 return 1;
}

<= /div>
int f()
{
=C2=A0=C2=A0=C2=A0 return 2;
=
}

constexpr auto a =3D f();=C2=A0=C2=A0=C2=A0 // a = =3D 1
auto fun =3D std::function<int(void)>(f);
int b =3D fun();=C2=A0=C2=A0 // b =3D 2

If th= ere is some interest, I can star working in a gcc fork as a prototype.
<= br>
BRgds,

=C2=A0=C2=A0=C2=A0 Daniel.


=
--
Who=E2=80=99s got the sweet= est disposition?
One guess, that=E2=80=99s who?
Who=E2=80=99d never, = ever start an argument?
Who never shows a bit of temperament?
Who'= ;s never wrong but always right?
Who'd never dream of starting a fig= ht?
Who get stuck with all the bad luck?

--
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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/CAFdMc-2q3KpV%2Bm5cfWr6b02XmHVUdxsNCNAVFG%2Bmz= Cv0QY7ZRg%40mail.gmail.com.

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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.
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