220 27871 article Path: news.gmane.org!.POSTED!not-for-mail From: Shahms King Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: pointer that propagates it's modifiers to the value Date: Mon, 22 Aug 2016 18:11:34 +0000 Lines: 118 Approved: news@gmane.org Message-ID: References: <28cf9d88-64c9-47c4-83f9-46843d869150@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a1140a1b410c1cb053aacfb18 X-Trace: blaine.gmane.org 1471889511 17455 195.159.176.226 (22 Aug 2016 18:11:51 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 22 Aug 2016 18:11:51 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC7ML3M6QIDBBYMA5W6QKGQENSU7JWY@isocpp.org Mon Aug 22 20:11:46 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f197.google.com ([209.85.213.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bbthJ-000491-FK for gclcip-std-proposals@m.gmane.org; Mon, 22 Aug 2016 20:11:45 +0200 Original-Received: by mail-yb0-f197.google.com with SMTP id g67sf258534731ybi.0 for ; Mon, 22 Aug 2016 11:11:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=1oxqjL6DBhc1DzoSvZ73uuFMDPCb9hv7UPUji+LF9O0=; b=i6LweHpyis9OpXh5YWpDqQLngef3hbTaZgTd8z2+ZcYkhwRg2IZjSxTqeA5/rqvVYl 1MrqyX26JAjncbBMOniuEy11VJs3pYEZNzXLXNS1Mn0qeoCiNsSuWllT5eJNp1DToBYW u1zV995dP3Zj842zaTZuj+3CnSrrhTUZIKT5koT3hqVMmIsPFNm3UUlLXz5fjXxzgkWZ pBz9XWGg7ptIgUXfsD6A21DWMB1IH4wSPDYXcaxsge4zNoBP33dqiToe6jqEkOg+DkLJ p4L8iBSui4R96Wy61YbaUIh6SrO7kRK4uqSmsvptxUihaT5AmxnZXK9XyPrQcHJEao1t SXuw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=1oxqjL6DBhc1DzoSvZ73uuFMDPCb9hv7UPUji+LF9O0=; b=lrP2zXpBS/ZD10Jl830SzfJBCfs+b4ro7/YNlZaHg76LvuCojnuz2FhVZsRkgERnBP hP9jvse4FGMQbxFtqerNDhgR78WiAU9cdqAg6BUvz4oAWbi63lXWLjp+mag32GhtcZon bQSXa03JRdBcHKBZrtC/Ee6TPGlOIL+nmVVS3W72Z8jVFOp3j9998tj6qZV9FqhEyCFS Lo8ZolJ/ZQt7c0ChBbbmWOsZtaTQHzjxUwWw1Bt0Bq5eySpdlOyARyPGjSJIw9sOSlb1 vTJkORCnX3clqIpLiipOCAkIXYXWnsgDAwZneyDA0ADmSLbtVIGE8Cj21VnaemHnySAa 8v9Q== X-Gm-Message-State: AEkoouspoOwKUnZR0CfQQeZOCUBe9RzFjYR+mGn4TGD7mh+10YXJMJDv8i97w9jWEfOV/g== X-Received: by 10.36.228.140 with SMTP id o134mr15392811ith.1.1471889505764; Mon, 22 Aug 2016 11:11:45 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.138.146 with SMTP id c18ls4200301ioj.10.gmail; Mon, 22 Aug 2016 11:11:44 -0700 (PDT) X-Received: by 10.36.200.131 with SMTP id w125mr22917199itf.33.1471889504892; Mon, 22 Aug 2016 11:11:44 -0700 (PDT) Original-Received: from mail-it0-x22c.google.com (mail-it0-x22c.google.com. [2607:f8b0:4001:c0b::22c]) by mx.google.com with ESMTPS id p137si17898732itb.29.2016.08.22.11.11.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Aug 2016 11:11:44 -0700 (PDT) Received-SPF: pass (google.com: domain of shahms.king@gmail.com designates 2607:f8b0:4001:c0b::22c as permitted sender) client-ip=2607:f8b0:4001:c0b::22c; Original-Received: by mail-it0-x22c.google.com with SMTP id e63so101343043ith.1 for ; Mon, 22 Aug 2016 11:11:44 -0700 (PDT) X-Received: by 10.107.162.16 with SMTP id l16mr28197800ioe.106.1471889504511; Mon, 22 Aug 2016 11:11:44 -0700 (PDT) In-Reply-To: <28cf9d88-64c9-47c4-83f9-46843d869150@isocpp.org> X-Original-Sender: shahms.king@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of shahms.king@gmail.com designates 2607:f8b0:4001:c0b::22c as permitted sender) smtp.mailfrom=shahms.king@gmail.com; dmarc=pass (p=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:27871 Archived-At: --001a1140a1b410c1cb053aacfb18 Content-Type: text/plain; charset=UTF-8 http://en.cppreference.com/w/cpp/experimental/propagate_const --Shahms On Mon, Aug 22, 2016 at 10:54 AM Alexey Mamontov wrote: > The idea is simple. I need to have some member by pointer (using the > abstract base class, for example), but I want it to behave absolutely the > same as member by value - it must inherit the constantness of this. > > Lets call it member_ptr and see what I mean: > > T * member_ptr::operator->(); > const T * member_ptr::operator->() const; > > T & member_ptr::operator*(); > const T & member_ptr::operator*() const; > > struct B > { > void f() = 0; > void f() const = 0; > }; > struct S > { > member_ptr m; > }; > > S s; > s.m->f(); // void f() is called > const S cs; > cs.m->f(); // void f() const is called > > All other modifiers (volatile, rvalue) must be forwarded as well... > > -- > 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/28cf9d88-64c9-47c4-83f9-46843d869150%40isocpp.org > > . > -- 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/CAFmGaCoxuJ9LwinSRe3fV%3DWGwNmHOFNeyqsxajSicFzzsG_ogg%40mail.gmail.com. --001a1140a1b410c1cb053aacfb18 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Mon, Aug 22, 2016 at 10:54 AM Alexey Mamontov <= ;caracrist@gmail.com> wrote:<= br>
The idea is s= imple.=C2=A0I need to have some member by pointer (using the abstract base = class, for example), but I want it to behave absolutely the same as member = by value - it must inherit the constantness of this.

Lets call it member_ptr<T> and see what I mean:
T *=C2=A0member_ptr<T>::operator->();
const = T * member_ptr<T>::operator->() const;

T & = member_ptr<T>::operator*();
const T=C2=A0& member_ptr&l= t;T>::operator*() const;

struct B
{
=C2=A0void f() =3D 0;
=C2=A0void f() const =3D 0;
<= div>};
struct S
{
=C2=A0member_ptr<B> m= ;
};

S s;
s.m->f(); // void= f() is called
const S cs;
cs.m->f(); // void f() const is= called

All other modifiers (volatile, rvalue) mus= t be=C2=A0forwarded as well...=C2=A0

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