220 31756 article Path: news.gmane.org!.POSTED!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allow constexpr static data members in a literal type. 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[2607:f8b0:4003:c0f::235]) by mx.google.com with ESMTPS id v188si4107674oib.107.2017.03.26.07.35.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Mar 2017 07:35:40 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4003:c0f::235 as permitted sender) client-ip=2607:f8b0:4003:c0f::235; Original-Received: by mail-ot0-x235.google.com with SMTP id y88so16851341ota.2 for ; Sun, 26 Mar 2017 07:35:40 -0700 (PDT) X-Received: by 10.157.58.68 with SMTP id j62mr9092896otc.145.1490538939990; Sun, 26 Mar 2017 07:35:39 -0700 (PDT) Original-Received: by 10.157.13.22 with HTTP; Sun, 26 Mar 2017 07:35:39 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4003:c0f::235 as permitted sender) smtp.mailfrom=ville.voutilainen@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:31756 Archived-At: On 26 March 2017 at 17:30, Avi Kivity wrote: > Consider this type-safe bool class: > > > template > > class bool_class { > > bool _value; > > public: > > explicit constexpr bool_class(bool v) noexcept : _value(v) {} > > // more emulation of bool > > static constexpr bool_class yes = bool_class{true}; > > static constexpr bool_class no = bool_class{true}; > > }; > > > Compilation fails, I believe rightly, on clang, because by the time yes and > no are parsed, bool_class is an incomplete type, and therefore not a literal > type. It could be worked around by making yes and no functions. > > Should we make this legal? It seems reasonable for types to offer constants > scoped under their own name, and if they are literal types, that these > constants can be constexpr. This is US 24 in http://open-std.org/JTC1/SC22/WG21/docs/papers/2016/p0488r0.pdf. The comment was rejected for C++17 due to lack of a proper proposal and the timing. -- 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/CAFk2RUa1uC%2BtvkBBYevwNFo%3Dh-oW7UXyBFXbnfoqmCAWFTEfOw%40mail.gmail.com. .