220 30236 <8747ddc6-c416-44b9-a8a0-b3a00f835c05@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: enum_cast proposal Date: Wed, 4 Jan 2017 08:33:28 -0800 (PST) Lines: 117 Approved: news@gmane.org Message-ID: <8747ddc6-c416-44b9-a8a0-b3a00f835c05@isocpp.org> References: <64617344.0Ggdhq6B90@tjmaciei-mobl1> <10490049.adee8Rr8fZ@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_4063_1935462667.1483547608425" X-Trace: blaine.gmane.org 1483547620 23403 195.159.176.226 (4 Jan 2017 16:33:40 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 4 Jan 2017 16:33:40 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBWOHWTBQKGQEG56SI2Y@isocpp.org Wed Jan 04 17:33:34 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cOoVB-0004Rq-TS for gclcip-std-proposals@m.gmane.org; Wed, 04 Jan 2017 17:33:26 +0100 Original-Received: by mail-pg0-f72.google.com with SMTP id 5sf907547065pgj.6 for ; Wed, 04 Jan 2017 08:33:30 -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=SYWRFNObTy0PDxD2hG3xS163HfcQvzNTqbpa53nulnI=; b=Lde8slAeLZYCt6FskphP+6Gczv4vp3SCGONWKkih5kHbyIg/RvyBlKvNKpo/ISEEWJ A4lq8cGBHZVZGJXUY1gyIIncpauFHJomJ8LE6Mod/GL8gvtSdNcHtYxR4fyanK6A5eZq +X2LOvG0gnbkKsxstfQcA8YpojK04cCW239Wmnh6vdEGEy3sjCGf/SQU9mcuJibgFlqJ ISeCgdjUbhe1NJN97YePjhDWfzSMfjQHQau9tQHL/m8g3mr/dFS3fZ1KqD2KJezebyyq K9m715Ql49XCKKsbRhCnuNEDnTIDUpenB4twpQq+Njhs+a4cRjC+XU0jG01L3ANxfgqh hOQQ== 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=SYWRFNObTy0PDxD2hG3xS163HfcQvzNTqbpa53nulnI=; b=TVfl86Qz793km4XxNDTPMS71FMsFRRtJwfcc9Iqyh5neWfXx0SXf8sNsUXAonwHIjv RXpRtPvd3KQtwv5NlC4O1r4fk0ZLoTDcMVyCREB8bUyBaRbYCHCGFNZFjWMNaKVAHSBj ugVeZCxsL4jX/ZshYqiE82/BIdnwJx1OZD2Hiq7mPLuuuYlhZ/q2nAphKTFf8o1RWgU0 x/PrjCux3ldjQc6sSSfna1AZKK+v8ODC7omSQ+WI81+JO9tXkA+sOWuXMUs33s7a63Mv j40vuXCFiWdHZhhOw3kXbCSLQY6tfxNFecKYmsZ45sW870asshTbNYQds1RLu8C0ZLvZ O4Qw== 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=SYWRFNObTy0PDxD2hG3xS163HfcQvzNTqbpa53nulnI=; b=EbvcS/QbX9kDAPilv2bsp9Mc8R5Eui48EudeXCxhLqsfsdT+5kaLqWgvvXcmdtlLG3 6DAscBL5rL1nfiE+UT3snH5hTG61rTf91uyGsgh1/B9pbXb0neKgKViZhqEZdvvoxUZt NH93cMdxyYUG2GYnddxRqu08yl6ud3jIiIRPZn+dCA6VSXgTw0HhYH/L4sxOxLwkQ7Zq OqR6xlscVPPncI8ImGAMDYIHD67RZDRlXFYu2Fel/GZqubZ7IhwZf2KYvFh8cOcPM4Ov PBu/HK84hD2lwDA3nv31saJTsDFC/nZW/rFGL99N+HKYnFVLUawdoBtMF+/M0gHkIKyt 1Asw== X-Gm-Message-State: AIkVDXJUtJL5j8hX9X+P1tuY8hcJu8U5z2LQQ2kvJlLKYFUFetKHAx60GWsrXdkr12sVfg== X-Received: by 10.99.9.1 with SMTP id 1mr38769568pgj.66.1483547609812; Wed, 04 Jan 2017 08:33:29 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.33.198 with SMTP id s64ls32347348otb.22.gmail; Wed, 04 Jan 2017 08:33:29 -0800 (PST) X-Received: by 10.157.42.16 with SMTP id t16mr2242716ota.18.1483547609035; Wed, 04 Jan 2017 08:33:29 -0800 (PST) In-Reply-To: <10490049.adee8Rr8fZ@tjmaciei-mobl1> X-Original-Sender: jmckesson@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:30236 Archived-At: ------=_Part_4063_1935462667.1483547608425 Content-Type: multipart/alternative; boundary="----=_Part_4064_689798405.1483547608425" ------=_Part_4064_689798405.1483547608425 Content-Type: text/plain; charset=UTF-8 On Wednesday, January 4, 2017 at 11:16:17 AM UTC-5, Thiago Macieira wrote: > > On quarta-feira, 4 de janeiro de 2017 07:20:11 BRST m.ce...@gmail.com > wrote: > > Why do you want to use some compiler invented type instead? > > If enum_cast is a function in standard library, why can't it use another > > type from same library? > > Then it is a function in the standard library. That means it needs to be > based > on something else to perform the check, like reflection. > There are plenty of functions in the standard library whose implementations rely on compiler-specific features. You wouldn't be able to implement most of the type traits without compiler intrinsic or some compiler-specific knowledge. You can't implement `type_info` or `initializer_list` without the compiler being involved. And so forth. This would simply be one more compiler-based construct. Once we get compile-time reflection, implementations could become platform-neutral (though the compiler-equivalent would probably still get faster). But how the function gets implemented ultimately has nothing to do with having it return `std::optional`. > > -- > Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org > Software Architect - Intel Open Source Technology Center > > -- 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/8747ddc6-c416-44b9-a8a0-b3a00f835c05%40isocpp.org. ------=_Part_4064_689798405.1483547608425 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wednesday, January 4, 2017 at 11:16:17 AM UTC-5= , Thiago Macieira wrote:
On qua= rta-feira, 4 de janeiro de 2017 07:20:11 BRST m.ce...@gmail.com wrote:
> Why do you want to use some compiler invented type instead?
> If enum_cast is a function in standard library, why can't it u= se another
> type from same library?

Then it is a function in the standard library. That means it needs to b= e based=20
on something else to perform the check, like reflection.

There are plenty of functions in the standard library whose impl= ementations rely on compiler-specific features. You wouldn't be able to= implement most of the type traits without compiler intrinsic or some compi= ler-specific knowledge. You can't implement `type_info` or `initializer= _list` without the compiler being involved. And so forth.

This would= simply be one more compiler-based construct. Once we get compile-time refl= ection, implementations could become platform-neutral (though the compiler-= equivalent would probably still get faster).

But how the function ge= ts implemented ultimately has nothing to do with having it return `std::opt= ional`.
=C2=A0

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

--
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 https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/8747ddc6-c416-44b9-a8a0-b3a00f835c05= %40isocpp.org.
------=_Part_4064_689798405.1483547608425-- ------=_Part_4063_1935462667.1483547608425-- .