220 30172 article Path: news.gmane.org!.POSTED!not-for-mail From: m.cencora@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: enum_cast proposal Date: Tue, 3 Jan 2017 07:06:10 -0800 (PST) Lines: 200 Approved: news@gmane.org Message-ID: References: <1483532086.2yCkjVBYWJ@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_20_332083105.1483455970154" X-Trace: blaine.gmane.org 1483455984 25888 195.159.176.226 (3 Jan 2017 15:06:24 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 3 Jan 2017 15:06:24 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD7YFUMJRYMBBYX3V3BQKGQEH6MA3GY@isocpp.org Tue Jan 03 16:06:15 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f71.google.com ([209.85.214.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cOQf9-0004pR-CN for gclcip-std-proposals@m.gmane.org; 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Tue, 03 Jan 2017 07:06:11 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.59.34 with SMTP id z31ls25171511otb.21.gmail; Tue, 03 Jan 2017 07:06:10 -0800 (PST) X-Received: by 10.157.17.167 with SMTP id v36mr2848291otf.12.1483455970618; Tue, 03 Jan 2017 07:06:10 -0800 (PST) In-Reply-To: <1483532086.2yCkjVBYWJ@tjmaciei-mobl1> X-Original-Sender: m.cencora@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:30172 Archived-At: ------=_Part_20_332083105.1483455970154 Content-Type: multipart/alternative; boundary="----=_Part_21_340188439.1483455970154" ------=_Part_21_340188439.1483455970154 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable W dniu wtorek, 3 stycznia 2017 15:25:25 UTC+1 u=C5=BCytkownik Thiago Maciei= ra=20 napisa=C5=82: > > On ter=C3=A7a-feira, 3 de janeiro de 2017 01:56:05 BRST m.ce...@gmail.com= =20 > wrote:=20 > > template =20 > > optional enum_cast(Int value);=20 > >=20 > > requires: is_enum, is_integral=20 > >=20 > > enum color=20 > > {=20 > > red =3D 1,=20 > > green =3D 200,=20 > > blue =3D 3=20 > > };=20 > > How do you see compilers implementing:=20 > > void f(int x)=20 > {=20 > enum_cast(x);=20 > }=20 > > Compiler should synthesize a function like below: optional enum_cast(int x) { switch(x) { case red: case green: case blue: return static_cast(x); default: return nullopt; } } Of course it could implement it more efficently (as range check instead of= =20 switch if all enumerators are consecutive integers). Regards, Maciej =20 > --=20 > Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org=20 > Software Architect - Intel Open Source Technology Center=20 > > --=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/bb835a83-0f69-4a76-97df-581c2a2ae8d8%40isocpp.or= g. ------=_Part_21_340188439.1483455970154 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
W dniu wtorek, 3 stycznia 2017 15:25:25 UTC+1 u=C5=BCytkow= nik Thiago Macieira napisa=C5=82:
On ter=C3=A7a-feira, 3 de janeiro de 2017 01:56:05 BRST m.ce...@gmail.com= wrote:
> template <typename Enum, typename Int>
> optional<Enum> enum_cast(Int value);
>=20
> requires: is_enum<Enum>, is_integral<Int>
>=20
> enum color
> {
> =C2=A0 =C2=A0red =3D 1,
> =C2=A0 =C2=A0green =3D 200,
> =C2=A0 =C2=A0blue =3D 3
> };

How do you see compilers implementing:

void f(int x)
{
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0enum_cast<color>(= x);
}



Compiler should synthes= ize a function like below:

o= ptional<= ;color>= enum_cast= (int x)
{
=C2=A0 =C2=A0 switch(x)
=C2=A0 =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 case red:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 case green:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 case blue:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return static_cast<color>(x);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 default:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return= nullopt;
=C2=A0 =C2=A0 }
}
Of course it could implement it more efficently (as range chec= k instead of switch if all enumerators are consecutive integers).

Regards,
Maciej
=C2=A0
--=20
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
=C2=A0 =C2=A0Software Architect - Intel Open Source Technology Center

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