220 37491 <2f3f1821-385e-4357-bcf4-9a87312853fe@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: florian.csdt@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allowing std::complex's magic permission for other types Date: Tue, 27 Mar 2018 02:53:23 -0700 (PDT) Lines: 195 Approved: news@gmane.org Message-ID: <2f3f1821-385e-4357-bcf4-9a87312853fe@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_17608_1844072844.1522144403475" X-Trace: blaine.gmane.org 1522144283 15304 195.159.176.226 (27 Mar 2018 09:51:23 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 27 Mar 2018 09:51:23 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC26HM4V3MIRBFFJ5DKQKGQE5ZEPS2A@isocpp.org Tue Mar 27 11:51:19 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f197.google.com ([209.85.217.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f0lGA-0003px-MV for gclcip-std-proposals@m.gmane.org; Tue, 27 Mar 2018 11:51:18 +0200 Original-Received: by mail-ua0-f197.google.com with SMTP id r1sf14985089uae.6 for ; Tue, 27 Mar 2018 02:53:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=38zN1OZAz5eWEW+AerypdRGwddGTm4DTtog11VUHj1Y=; b=unQ/mWi4SRqLEL/EJgD8/MiHZ9RE7PnJGLaCQXhboF6voBY/ec7bDsZ2lH+MWcFIpq AIUcf0CBouXUO1WhmWALr7z46WVbiWnV2qu9yG/9KUhNlbck0PBqNkZdKiM0h8eNnd6L oEXq22NrjuO+Sz4dU93TsUkIhwp9zaejZNf/0YvSdtwgO1clSvQVqsf+xeEYTz+xfAEL laxpk5LMvunJgYicN+/YGaceSaa9oXYIbIkDdzWyBaMzs3vuY+0YNvpGqCAwz1ln8IY+ DbEZ9/cMNZrgQej8TxYxkWZbwheF7GJETnCWv8e98Ma5R4WC1/4TARmouF9nEBGeRlE/ 0fhQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=38zN1OZAz5eWEW+AerypdRGwddGTm4DTtog11VUHj1Y=; b=pRPB3TKBv1beulk/We/Nw5jI33SmQaH0i7klh64lDFrtG9bFrGJSV4hOp3vsjoIGSr 5lHeDAhgy4S3og32EceWjraxoTAcN8C1hns7sEtS4x3ae/1XSHNmrm/6oXDLOnnDxyYT q7BkyvzXKPi9CjhzVcRAsjxe/Ln7Vh29rDWCkhKv1U3VQThHuuw+BL2hhrCXgUOX2qjZ fOZLzPgOU0yk0kFJdmcOD27I4npftWQTSw7gR8JQkkd7dR2DVPg9EAttbeqP8htF4Lvf oy7y9ag9Fc5QcSokOyfA3A9UXHgI/3nsahslUgyweDyRtGLa+vvU5UTR4eA36vkR+AJq L7XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=38zN1OZAz5eWEW+AerypdRGwddGTm4DTtog11VUHj1Y=; b=I4QP1mf+9WT56eTK2vElQkL3mQzsSs2hnRnVc/acc9DQ7z4cCrn4qpsR86U1PR/ujE HFaLWs//nf4yvIlfp0oF1ealWgsqaqn0gCAoWj2aYkIjTUcwMZEwOpThFxlv3EW6p0yp 8WTUF1x9wh2lad0GAj3l3d8hQb2tuVAQDSD8XexXHhvzYpzG7VhMtv7JiRDlvJ3ol1rk 6HKX1X2pm6nCiLGucdWz0sLWHnYIdL66CID89rJoi4FecOzNY3N9S1OvH/UkgpTnhbei nOB3UBJoc4FZZ8pgmqCqtngRWmp6wQgSeAT1wbvT2bCHbZ6a3QotWP1EMhh+sCIBxQu7 isHg== X-Gm-Message-State: AElRT7FWz2+Rl2pB2N2ZSoMJjSW4RDx0omBMn0MuK8san68dA5EnSCFj dYsh7I82Sx27BeFX2Jq+UJ+iLA== X-Google-Smtp-Source: AG47ELsBn68v/dgn1bBAKQw0KkRhZANnNX3yqAOzJHrrJ6ZWQtUdTkLuhfTAIhz6P9BtbgenaO62qg== X-Received: by 10.31.130.15 with SMTP id e15mr18393664vkd.115.1522144405740; Tue, 27 Mar 2018 02:53:25 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.161.86 with SMTP id k83ls343139vke.4.gmail; Tue, 27 Mar 2018 02:53:24 -0700 (PDT) X-Received: by 10.31.158.83 with SMTP id h80mr5284510vke.9.1522144404085; Tue, 27 Mar 2018 02:53:24 -0700 (PDT) In-Reply-To: X-Original-Sender: florian.csdt@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:37491 Archived-At: ------=_Part_17608_1844072844.1522144403475 Content-Type: multipart/alternative; boundary="----=_Part_17609_1346117342.1522144403475" ------=_Part_17609_1346117342.1522144403475 Content-Type: text/plain; charset="UTF-8" I have the impression that people are missing the big picture here. I see one big problem that can be solved with overloadable reinterpret_cast: smart pointers. If you look closely at shared_pointer for instance, you will see: template std::shared_ptr static_pointer_cast(const std::shared_ptr& r) noexcept ; template std::shared_ptr dynamic_pointer_cast(const std::shared_ptr& r) noexcept; template std::shared_ptr const_pointer_cast(const std::shared_ptr& r) noexcept; template std::shared_ptr reinterpret_pointer_cast(const std::shared_ptr& r) noexcept; If it were possible to overload dynamic_cast const_cast and reinterpret_cast, this would have been unnecessary to have a different interface for shared pointers than for regular pointers. -- 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/2f3f1821-385e-4357-bcf4-9a87312853fe%40isocpp.org. ------=_Part_17609_1346117342.1522144403475 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I have the impression that people are missing the big pict= ure here.

I see one big problem that can be solved with overloadable= reinterpret_cast: smart pointers.
If you look closely at shared_pointer= for instance, you will see:

template <class T= , class U>
std::shared_ptr<T> sta= tic_pointer_cast(con= st std::shared_ptr<U>& r) noexcept;

template <class T<= /span>, class U>
std::shared_ptr<T> dyn= amic_pointer_cast(co= nst std::shared_ptr<U>& r) noexcept;

template <class T, class U><= span style=3D"color: #000;" class=3D"styled-by-prettify">
std::shared_ptr<T> const_pointer_cast(const std::shared_ptr<U>&= ; r= ) noexcept;

template <= ;class T, class U>
std::shared_ptr<T> reinterpret_p= ointer_cast(const std::shared_ptr<U>& r) noexcept;

If it were possible to overlo= ad dynamic_cast const_cast and reinterpret_cast, this would have been unnec= essary to have a different interface for shared pointers than for regular p= ointers.

=

--
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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/2f3f1821-385e-4357-bcf4-9a87312853fe= %40isocpp.org.
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