220 41138 article Path: news.gmane.org!.POSTED!not-for-mail From: Bernardo Sulzbach Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: Extensions of Scoped Enumerations Date: Thu, 29 Nov 2018 21:09:51 -0200 Lines: 71 Approved: news@gmane.org Message-ID: References: <506ba0a8-2d6b-4a4d-8fe8-b5e94d232365@isocpp.org> <82c331a0-fb81-4b67-8a7e-c5a6b8929e00@isocpp.org> 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 1543532883 6477 195.159.176.226 (29 Nov 2018 23:08:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 29 Nov 2018 23:08:03 +0000 (UTC) Cc: philipgins@gmail.com To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCPLFUPA7QIRBTHDQHQAKGQERRNQGVY@isocpp.org Fri Nov 30 00:07:58 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf1-f197.google.com ([209.85.210.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gSVPX-0001S7-3W for gclcip-std-proposals@m.gmane.org; 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[209.85.215.176]) by smtp.gmail.com with ESMTPSA id l11sm4136536pff.65.2018.11.29.15.10.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Nov 2018 15:10:03 -0800 (PST) Original-Received: by mail-pg1-f176.google.com with SMTP id d72so1606321pga.9 for ; Thu, 29 Nov 2018 15:10:03 -0800 (PST) X-Received: by 2002:a62:6303:: with SMTP id x3mr3420931pfb.110.1543533002751; Thu, 29 Nov 2018 15:10:02 -0800 (PST) In-Reply-To: <82c331a0-fb81-4b67-8a7e-c5a6b8929e00@isocpp.org> X-Gmail-Original-Message-ID: X-Original-Sender: sulzbachbernardo@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of sulzbachbernardo@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=sulzbachbernardo@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:41138 Archived-At: I think this might be a very useful feature. For instance, when transitioning from API A to API B (the next major version of A), B signatures could use a subtype of the enumeration used in A during the transition period. This would be better than adding unsupported values to the A enumeration and better than simply repeating the already existing constants in the new enumeration. On Thu, Nov 29, 2018 at 8:34 PM Bengt Gustafsson wrote: > > I like your idea, but I am pretty sure it has been proposed and declined = before. If my memory serves me there were perceived issues with duplicate e= numerator values and possibly whether a sub-enum should be able to change t= he value of a parent enumerator (in keeping with how a subclass can overrid= e a name). I think you have to address this and I would suggest that you us= e a "as if" strategy stating that the sub-enum is to be defined as if the a= dded enumerators were textually appended to those of the base-enum. > > Maybe you should also specify if it is legal to not add any additional en= umerators in the sub-enum, and if allowed, exactly what this means. > > Possibly the issue of multiple inheritance should be addressed to. Probab= ly best to forbid this, but it could be of interest to merge sets of values= , and it could possibly be legal if there are no common enumerator names or= values in both base-enums, except if both the enumerator and value are the= same (and any specified underlying type of course). > > Den torsdag 29 november 2018 kl. 19:24:47 UTC+1 skrev phili...@gmail.com: >> >> Hello, >> >> After receiving positive feedback on the sg14 mailing list, I'd now like= to share my proposal here. >> >> Abstract: >> Scoped enumerations (=E2=80=9Cenum classes=E2=80=9D) provide a type safe= alternative to C-style enums. >> It can be desirable to have enumerations that share a subset of their en= umerators and >> there is a natural correspondence between subtyping and adding enumerato= rs to enums. >> This proposal is for a simple, sound and practically useful extension to= the core language >> standard to provide a mechanism for subtyping scoped enumerations. >> >> The complete proposal can be read here and an implementation is availabl= e on github. >> I'm looking forward to your feedback! >> >> Thanks, >> Philip Ginsbach > > -- > 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/isoc= pp.org/d/msgid/std-proposals/82c331a0-fb81-4b67-8a7e-c5a6b8929e00%40isocpp.= org. --=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/CAMSdZ4Zf%2B0meeQ4hzwZVZ_j88u5gpB_qd_XmsR-OfrhCy= Yndhw%40mail.gmail.com. .