220 30218 <1730f9cb-837d-4af3-a771-107e21de0adc@isocpp.org> 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: Wed, 4 Jan 2017 00:44:09 -0800 (PST) Lines: 157 Approved: news@gmane.org Message-ID: <1730f9cb-837d-4af3-a771-107e21de0adc@isocpp.org> References: <2998762.etaySSRi7N@tjmaciei-mobl1> <42463446.MPeEFdAbRV@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2725_666972437.1483519450024" X-Trace: blaine.gmane.org 1483519456 6868 195.159.176.226 (4 Jan 2017 08:44:16 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 4 Jan 2017 08:44:16 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD7YFUMJRYMBBWXLWLBQKGQEKBVD4SY@isocpp.org Wed Jan 04 09:44:12 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f197.google.com ([209.85.213.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cOhB1-0000QJ-8r for gclcip-std-proposals@m.gmane.org; Wed, 04 Jan 2017 09:44:07 +0100 Original-Received: by mail-yb0-f197.google.com with SMTP id 186sf402442659yby.5 for ; Wed, 04 Jan 2017 00:44:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to: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=XMwqCEIWm3hVdGE46aLG5dRMOTUnREI1bvixKrT2zaQ=; b=gEgdiOmxLEDWXqydfzlpAb18//vr1OTDEiCBeNd5CVuA8JbtYoHO1Gx1TQtc1ErSkr vtt/t9n0dCAPxMelDYI/cdCSqz7o3TI8q3FRK2zrbxkbbCaDV+8AT1w4nkLfu/2wbKBO 6ugeDva0ry/HPLntoMB6OUqbTVU6+pQoiXPr4vgDp9p2b0djfW1WU0RXQ24jS+Pg/CBG ocGyZnBy5eMO4jXtoKid6+NdmL7djeEl5gvGF1PxB7FOHz9EcRjpVXkkfvGnjqdIPZbd M9owwtvyHpmFRaoZJ+0DpO6/ExVEMYQ+muAZ+hQPVMx4JPGa0LV948pJddgZX0BU4E0/ 954Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to: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=XMwqCEIWm3hVdGE46aLG5dRMOTUnREI1bvixKrT2zaQ=; b=EGaQBZtGYVjWv1ZSXEPntcSfrx00H7KudIBcUKDwgpcWjKn0rOPpwsEmTIumM2xclr 8hVSx3/xBGZShEMvhOgRTbDKTYhaUhrzDv9xXAtoxR07RvhyEvDkLiA573nI9qrpK8wM kpX3flev029wmZEQYfbNLG1yBbB3aDbeXK0UYfax54krtd8m+9ZpLyTzvRV4BLCGwW/e F4ZmFFylA4zsd4riA+waazsjwWWLOv95ZlBnsvfNXLQSdm7SEGaVEDHdgiDtd6BYgIiJ 40Z/OrVkt5bsTay88jfnSlOf2+m28UspI11dswbGSVObLYl087pwRDSyVV0+U3DrycZl ufxw== 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: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=XMwqCEIWm3hVdGE46aLG5dRMOTUnREI1bvixKrT2zaQ=; b=ok+bmRTFJzS5EeVLjMLqB0TxsYrD1gPRrcvKQpQRiJE5Xae5ipOPTuBCfZPr7FXYfz GdD4bQYmPYsFeU2FRJg87G/Et1pb6c2XzAz8sSmj4stc7V3wjMRzohwfousQDigKxSTP IERqwL5/6D1O7T39MyPgpKgfMmUgHql3iYHPaXRgUE5++CuFr5mmk1lDRotErQOMzlLb vqAsDlYe19qs+O0mFpza6gE+sbgt4zI+ShWMFz0CSKIgVpEITtOSjZI2Eu+1eCjZqR30 AMHQU5bEtkwnZ1rPfFeaHFHAMpjtm2c9gWNGhz2xD+dhEEQQROAft85AR8o/sTGswkn4 9nhw== X-Gm-Message-State: AIkVDXIxmwBrqbRZk3rZVJ5dOJWctp6ugkoxRnqjRfO5hQlgd9r9w6YE6hLw8gfGS1rR7A== X-Received: by 10.129.96.67 with SMTP id u64mr19264209ywb.90.1483519451158; Wed, 04 Jan 2017 00:44:11 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.11.115 with SMTP id p48ls19808739otd.19.gmail; Wed, 04 Jan 2017 00:44:10 -0800 (PST) X-Received: by 10.157.17.3 with SMTP id g3mr3040149ote.8.1483519450433; Wed, 04 Jan 2017 00:44:10 -0800 (PST) In-Reply-To: <42463446.MPeEFdAbRV@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:30218 Archived-At: ------=_Part_2725_666972437.1483519450024 Content-Type: multipart/alternative; boundary="----=_Part_2726_901685433.1483519450024" ------=_Part_2726_901685433.1483519450024 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable W dniu wtorek, 3 stycznia 2017 20:12:38 UTC+1 u=C5=BCytkownik Thiago Maciei= ra=20 napisa=C5=82: > > On ter=C3=A7a-feira, 3 de janeiro de 2017 08:22:52 BRST m.ce...@gmail.com= =20 > wrote:=20 > > > How do you know whether a use of enum_cast is compile-time or whether= =20 > it=20 > > > is=20 > > > runtime?=20 > >=20 > > I don't know and I don't care. The function should be constexpr to=20 > support=20 > > both cases.=20 > > Well, I think people may care. A constexpr invocation has zero cost at=20 > runtime, since it will have failed to convert by producing an error=20 > message,=20 > or it will succeed by becoming a no-op (like static_cast, minus pointer= =20 > adjustment). But a non-constexpr invocation will have a runtime cost.=20 > Well of course it will have runtime cost in non-constexpr invocation, the whole point of this function is to perform validation at runtime. Constexpr support is just an addition. =20 > > What I'd like to hear now is whether anyone else would find such a=20 > > functionality useful?=20 > > Do you consider it a good idea to put it into C++ standard/library?=20 > > Maybe you should rename it to mean a check if the value is a valid=20 > enumerator=20 > and drop the "cast" part.=20 > I thought about it, but I see no use case for just a check. In all the use cases I can think of user wants the cast after the check. Do you have a example in mind where such a check without a cast later would be useful? =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/1730f9cb-837d-4af3-a771-107e21de0adc%40isocpp.or= g. ------=_Part_2726_901685433.1483519450024 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
W dniu wtorek, 3 stycznia 2017 20:12:38 UTC+1 u=C5=BCytkow= nik Thiago Macieira napisa=C5=82:
On ter=C3=A7a-feira, 3 de janeiro de 2017 08:22:52 BRST m.ce...@gmail.com= wrote:
> > How do you know whether a use of enum_cast is compile-time or= whether it
> > is
> > runtime?
>=20
> I don't know and I don't care. The function should be cons= texpr to support
> both cases.

Well, I think people may care. A constexpr invocation has zero cost at= =20
runtime, since it will have failed to convert by producing an error mes= sage,=20
or it will succeed by becoming a no-op (like static_cast, minus pointer= =20
adjustment). But a non-constexpr invocation will have a runtime cost.

Well of course it will have runtime co= st in non-constexpr invocation, the
whole point of this function = is to perform validation at runtime.
Constexpr support is just an= addition.
=C2=A0
> What I'd like to hear now is whether anyone else would find suc= h a
> functionality useful?
> Do you consider it a good idea to put it into C++ standard/library= ?

Maybe you should rename it to mean a check if the value is a valid enum= erator=20
and drop the "cast" part.

I thought about it, but I see no use c= ase for just a check.
In all the use cases I can think of user wa= nts the cast after the check.

Do you have a exampl= e in mind where such a check without a cast later
would be useful= ?
=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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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/1730f9cb-837d-4af3-a771-107e21de0adc= %40isocpp.org.
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