220 30815 article Path: news.gmane.org!.POSTED!not-for-mail From: "'Johannes Schaub' via ISO C++ Standard - Future Proposals" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Should names used in the initializer of an object of scoped enumeration type be looked up in the scope of the enum? 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[2607:f8b0:4003:c0f::22b]) by mx.google.com with ESMTPS id g10si1983227ote.47.2017.02.07.09.22.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Feb 2017 09:22:25 -0800 (PST) Received-SPF: pass (google.com: domain of schaub.johannes@googlemail.com designates 2607:f8b0:4003:c0f::22b as permitted sender) client-ip=2607:f8b0:4003:c0f::22b; Original-Received: by mail-ot0-x22b.google.com with SMTP id 32so91341105oth.3 for ; Tue, 07 Feb 2017 09:22:25 -0800 (PST) X-Received: by 10.157.40.139 with SMTP id s11mr9488055ota.226.1486488144583; Tue, 07 Feb 2017 09:22:24 -0800 (PST) Original-Received: by 10.74.60.23 with HTTP; Tue, 7 Feb 2017 09:22:24 -0800 (PST) In-Reply-To: <5899F95E.8060407@gmail.com> X-Original-Sender: schaub.johannes@googlemail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@googlemail.com; spf=pass (google.com: domain of schaub.johannes@googlemail.com designates 2607:f8b0:4003:c0f::22b as permitted sender) smtp.mailfrom=schaub.johannes@googlemail.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=googlemail.com X-Original-From: Johannes Schaub 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:30815 Archived-At: Alternatively, this can be merged with "strong typedefs", so that you can type (warning: bikeshed) typedef new enum { A, B, C } X; A new-type would depend on what it alias. Aliasing a new-type with an enumeration type creates pretty much what currently a scoped enumeration is, just as a "new" type without the strongly-scoping-thing. Aliasing a new-type with a class type would be ill-formed. Aliasing a new-type with an integer would create a new integer type.. Aliasing an array type would apply the new-type transformation onto the element type. Same for new-typing a pointer type. 2017-02-07 17:44 GMT+01:00 Matthew Woehlke : > On 2017-02-07 01:12, Brian Bi wrote: >> For example, should the following code be made well-formed? >> >> enum class Color { >> RED, >> GREEN, >> BLUE, >> }; >> >> Color color = RED; > > Not by itself, no. In general, *YES PLEASE*! > > My biggest hatred of strongly typed enums, and why I rarely use them, is > that they conflated two orthogonal features: implicit conversion (i.e. > that they *don't* implicitly convert), and scoping of the enumeration > values. > > Fortunately, C++11 made it legal to name enumerators by their containing > enumeration for both "classic" and "strongly typed" enumerations, which > lessens the need for weakly-typed, strongly-scoped enumerations. > However, there is as yet no good solution for strongly-typed, > weakly-scoped enumerations, despite a fairly common desire for such > critters. > > I'd like to see something like `using enum Color` to make the > enumerators of a named enumeration available in a different scope. > > Note that this would not be *just* the parent scope. For example: > > namespace zoo { > enum class Animal { Dog, Cat, Cow, Pig }; > } > namespace farm { using enum ::zoo::Animal; } > > auto x = farm::Dog; // okay; decltype(x) == ::zoo::Animal > > -- > Matthew > > -- > 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/5899F95E.8060407%40gmail.com. -- 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. 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