220 33164 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?Q?Daniel_Kr=C3=BCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Add a few missing things from the iterator library Date: Mon, 10 Jul 2017 20:21:23 +0200 Lines: 32 Approved: news@gmane.org Message-ID: References: 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 1499710887 1932 195.159.176.226 (10 Jul 2017 18:21:27 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 10 Jul 2017 18:21:27 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORBJELR7FQKGQEQIXJNYQ@isocpp.org Mon Jul 10 20:21:21 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f70.google.com ([209.85.215.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dUdJA-0000C7-Sm for gclcip-std-proposals@m.gmane.org; Mon, 10 Jul 2017 20:21:20 +0200 Original-Received: by mail-lf0-f70.google.com with SMTP id w198sf24732796lff.14 for ; 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[2a00:1450:400c:c0c::22a]) by mx.google.com with ESMTPS id b7si4534845wma.65.2017.07.10.11.21.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jul 2017 11:21:24 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c0c::22a as permitted sender) client-ip=2a00:1450:400c:c0c::22a; Original-Received: by mail-wr0-x22a.google.com with SMTP id 77so149608504wrb.1 for ; Mon, 10 Jul 2017 11:21:24 -0700 (PDT) X-Received: by 10.28.132.13 with SMTP id g13mr8837397wmd.58.1499710884063; Mon, 10 Jul 2017 11:21:24 -0700 (PDT) Original-Received: by 10.28.134.16 with HTTP; Mon, 10 Jul 2017 11:21:23 -0700 (PDT) In-Reply-To: X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.b=B+xfaFab; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c0c::22a as permitted sender) smtp.mailfrom=daniel.kruegler@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:33164 Archived-At: 2017-07-10 19:47 GMT+02:00 : > Hi, > > I propose to add to : [..] > 2) std::make_const_iterator(iterator) > Semantics: return iterator static_cast-ed to const_iterator > Why: We have std::make_move_iterator so again I believe this is missing. > Container requirements (23.2) specify that iterators must be convertible to > const_iterator so I believe this is just a static_cast. > > 3) std::container_of_t > Semantics: determine the container type of the iterator > Why: Helpful to implement 2 above, also helpful in a variety of situations > where there's a need to check requirements on the container of an iterator. These two proposals make assumptions that are neither met by current implementations nor implied by the standard: There is no 1:1 relation between container type and iterator type, which makes both (2) and (3) impossible. It would also break non-Standard-Library implementations of containers such as from Boost or other third-party libraries. - Daniel -- 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/CAGNvRgBnrZXiiQQy_8eVukE-F365uuXgwFMffvdNbyJ%2B_S%3DO2g%40mail.gmail.com. .