220 33451 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?Q?Daniel_Kr=C3=BCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Proposal: underlying_cast Date: Sun, 30 Jul 2017 19:05:26 +0200 Lines: 65 Approved: news@gmane.org Message-ID: References: <6a2c32ed-99b5-4cc5-86a5-ee3cc07567a3@isocpp.org> <2570492.NpxuI0RVu0@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1501434331 16213 195.159.176.226 (30 Jul 2017 17:05:31 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 30 Jul 2017 17:05:31 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORBV5D7DFQKGQEZKOVVCA@isocpp.org Sun Jul 30 19:05:24 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f70.google.com ([209.85.215.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dbrec-0003jb-L6 for gclcip-std-proposals@m.gmane.org; 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[2a00:1450:400c:c0c::236]) by mx.google.com with ESMTPS id m192si15843825wma.224.2017.07.30.10.05.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 30 Jul 2017 10:05:27 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c0c::236 as permitted sender) client-ip=2a00:1450:400c:c0c::236; Original-Received: by mail-wr0-x236.google.com with SMTP id f21so114556836wrf.5 for ; Sun, 30 Jul 2017 10:05:27 -0700 (PDT) X-Received: by 10.223.166.17 with SMTP id k17mr10591820wrc.243.1501434326934; Sun, 30 Jul 2017 10:05:26 -0700 (PDT) Original-Received: by 10.28.40.69 with HTTP; Sun, 30 Jul 2017 10:05:26 -0700 (PDT) In-Reply-To: X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=uWg1+rwi; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c0c::236 as permitted sender) smtp.mailfrom=daniel.kruegler@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=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:33451 Archived-At: 2017-07-30 18:58 GMT+02:00 Ville Voutilainen : > On 30 July 2017 at 19:37, Daniel Kr=C3=BCgler = wrote: >> 2017-07-30 18:34 GMT+02:00 Ville Voutilainen : >>> On 30 July 2017 at 19:20, Thiago Macieira wrote: >>>> On Sunday, 30 July 2017 04:50:41 PDT james.a.cooper@gmail.com wrote: >>>>> C++ allows enums to have an underlying type specified. When serialisi= ng >>>>> enum values it's important to use the correct type. >>>>> This proposal is to add a utility function that casts an enum type to= its >>>>> underlying value. This would make it easier to handle >>>>> enum types in function overloads for serialisation. For example: >>>>> >>>>> template >>>>> std::ostream& write(std::ostream& os, const T& v) >>>>> { >>>>> os << std::underlying_cast(v); >>>>> return os; >>>>> } >>>> >>>> Yes on the convenience, but "underlying_cast" is the wrong name becaus= e this >>>> does not look like a regular cast. >>>> >>>> Something like "std::underlying_value" might be better. >>> >>> Perhaps we should change std::underlying_type to be an identity type >>> for non-enums. >> >> Not for all of them, please. The term underlying type exists also for >> wchar_t, char16_t, and char32_t and is different from the identity >> type. > > > I'm not talking about any particular term, but the trait. I do as well. > It's > ill-formed to use it for a non-enum type today. I know. > I suppose having it return a non-identity type for the types you > mentioned would be remotely plausible. I wanted to ensure that we did no unintentionally define it as identity for non-enum types exactly due to the mentioned types for which the trait is currently not defined but where the term underling type has already a well-defined meaning. - Daniel --=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/CAGNvRgDH%3Deef%3DTWoXor1MedUw9xBzm3bgSZKqsREN_-= qaxTC_w%40mail.gmail.com. .