220 33789 <994d795d-3c10-7201-8386-12f5ec7bbaae@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 10:40:25 -0400 Lines: 32 Approved: news@gmane.org Message-ID: <994d795d-3c10-7201-8386-12f5ec7bbaae@gmail.com> References: <6ed2bd55-5538-418f-8f1a-263a9958babd@isocpp.org> <9979b017-fc21-445f-a1d1-0f55f8e7bf3d@isocpp.org> <3784a92f-9045-e0e8-df9f-51a68f66ac99@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 1502376037 29345 195.159.176.226 (10 Aug 2017 14:40:37 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 10 Aug 2017 14:40:37 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 Cc: ville.voutilainen@gmail.com, bop@gmb.dk To: std-proposals@isocpp.org, Nicol Bolas Original-X-From: std-proposals+bncBC37LBFWUIFBBYPAWHGAKGQECGN7IGA@isocpp.org Thu Aug 10 16:40:33 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f197.google.com ([209.85.161.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfodQ-00076k-32 for gclcip-std-proposals@m.gmane.org; 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[66.194.253.20]) by smtp.googlemail.com with ESMTPSA id f187sm3510712qkb.97.2017.08.10.07.40.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Aug 2017 07:40:32 -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=NchX4ttz; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:400d:c0d::244 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:33789 Archived-At: On 2017-08-10 10:18, Nicol Bolas wrote: > On Thursday, August 10, 2017 at 10:05:17 AM UTC-4, Matthew Woehlke wrote: >> On 2017-08-10 02:35, Ville Voutilainen wrote: >>> Gee, data() could just return a reference. >> >> ...which is only possible if it is okay for the user to directly assign >> to the underlying data member. If something non-trivial needs to happen >> when the property is assigned, then no, you'd need to return a proxy >> object. (And, alas, some_function would need to be a template.) > > Not to mention that it assumes that there is actually an object behind > `data()` that could be returned as a reference. Many properties are > phantasmal; the actual data is not stored in the type it appears as. > Indeed, one could say that the whole point of properties as a feature are > that they *can be* phantasmal in such a way, without the user being aware > of their nature. ....at least until someone tries to take/pass it as a reference to the "apparent" type ;-). In a strongly-typed language like C++, that's just insurmountable. (But I don't consider it a feature-killer.) Applying this to bitfields was mentioned earlier in the thread... -- Matthew -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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