220 33784 <05214462-9ca7-a5c8-018a-4a05faf02f7c@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: properties? Date: Thu, 10 Aug 2017 10:08:46 -0400 Lines: 35 Approved: news@gmane.org Message-ID: <05214462-9ca7-a5c8-018a-4a05faf02f7c@gmail.com> References: <6ed2bd55-5538-418f-8f1a-263a9958babd@isocpp.org> <10557c71-2b0f-6675-305e-1267eeda1ed6@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1502374148 5429 195.159.176.226 (10 Aug 2017 14:09:08 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 10 Aug 2017 14:09:08 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 Cc: evan.teran@gmail.com To: std-proposals@isocpp.org, Nicol Bolas Original-X-From: std-proposals+bncBC37LBFWUIFBB4GRWHGAKGQEODMXYEQ@isocpp.org Thu Aug 10 16:09:02 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f69.google.com ([74.125.83.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfo8h-0000Fi-Dj for gclcip-std-proposals@m.gmane.org; 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[66.194.253.20]) by smtp.googlemail.com with ESMTPSA id 55sm4394211qtm.51.2017.08.10.07.08.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Aug 2017 07:08:47 -0700 (PDT) Original-Newsgroups: gmane.comp.lang.c++.isocpp.proposals In-Reply-To: Content-Language: en-US X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=G/GOA8Rm; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:400d:c09::242 as permitted sender) smtp.mailfrom=mwoehlke.floss@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:33784 Archived-At: On 2017-08-09 16:20, Nicol Bolas wrote: > On Wednesday, August 9, 2017 at 1:59:24 PM UTC-4, Matthew Woehlke wrote: >> On 2017-08-09 13:32, Evan Teran wrote: > I poked around with the ideas for a while. The basic idea was to > provide 3 independently-useful features [...] stateless member > subobjects [...] inner classes [...] and language-support for > CRTP-base class (so that you could write the implementation of the > inner class outside of the inner class itself, and thus reuse > boilerplate).> > My biggest stumbling block was the latter. I realized that I was basically > creating "mixins," but though inheritance. The problem there is that the > derived class is incomplete until the template instantiation of the base > class, so the CRTP-base class can only access features of the derived class > within functions. That made doing simple things like iterator traits > impossible without some external class (like `iterator_traits`). > > So if I wanted to do mixins without a bunch of arbitrary limitations, > they'd need to not just be some base class using template trickery, but a > true, first-class feature that was separate from template instantiation. Ah. Of course, mixins are sufficiently wide-spread that figuring those out is almost certainly worthwhile in its own right. (I've always thought so, anyway.) Maybe someone would be interested in taking up the torch on those? -- 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/05214462-9ca7-a5c8-018a-4a05faf02f7c%40gmail.com. .