220 18787 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::vector - adding support for non-moveable, non-default constructible types with lambdas Date: Thu, 25 Jun 2015 22:07:49 +0300 Lines: 44 Approved: news@gmane.org Message-ID: References: <06317928-6af2-4133-a38e-8d6c829f311b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1435259293 4994 80.91.229.3 (25 Jun 2015 19:08:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 25 Jun 2015 19:08:13 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBBNDWGWAKGQE5GFX26Q@isocpp.org Thu Jun 25 21:07:59 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f199.google.com ([209.85.213.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Z8CV9-0005jz-TJ for gclcip-std-proposals@m.gmane.org; Thu, 25 Jun 2015 21:07:56 +0200 Original-Received: by igbqq3 with SMTP id qq3sf142197036igb.2 for ; Thu, 25 Jun 2015 12:07:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type: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=zt8Ob3yFWyy4IfiFJf52y3aIp5pUwntKf9x+NxoiFlM=; b=Yn+f50EDiMOzdu1+Vz/tgqevYTIvyYrjyz/7qUxnD82/nMLevZlzNRRwo5TAuz6s0G 65i9mdQxBaExP6hPwjaUO53NhX+7T+Rdg4zqwEvrwQ1mEsBSoMbFM5TSMpPqgEtCleFF t9MzLaZlas7QL1R6tKT5j42W5aHanhq6Twk+E4PKDzy9hcW5rE5ElsO8pXUXb2HtSovL cksgm/zVWmCF/l8V4KNfwGgbTkulhDDXBgbV9cxEbTMpYGzXRAQrHQuvosf3SXAl1PmC AfcDxS+vXY0FrdI9GCOBiUTVM8FsMDwaX2gZDqdiyzPwX89ouYXaWrItpLI5kAr05G6G INPQ== X-Gm-Message-State: ALoCoQmzW9ZnTjce1f/Gvb/C1cwrvtcWyrkViTPPabsI+Myn2EoldRS6QJO+nhhyFxuRRL2fvQQ+ X-Received: by 10.182.200.197 with SMTP id ju5mr61946897obc.28.1435259269956; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.66.147 with SMTP id f19ls2109916igt.43.canary; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) X-Received: by 10.107.8.210 with SMTP id h79mr40104758ioi.27.1435259269330; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) Original-Received: from mail-ig0-x230.google.com (mail-ig0-x230.google.com. [2607:f8b0:4001:c05::230]) by mx.google.com with ESMTPS id pf6si25981698icb.107.2015.06.25.12.07.49 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jun 2015 12:07:49 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4001:c05::230 as permitted sender) client-ip=2607:f8b0:4001:c05::230; Original-Received: by igin14 with SMTP id n14so62229358igi.1 for ; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) X-Received: by 10.50.30.105 with SMTP id r9mr6215877igh.11.1435259269209; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) Original-Received: by 10.36.152.7 with HTTP; Thu, 25 Jun 2015 12:07:49 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4001:c05::230 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@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-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:18787 Archived-At: On 25 June 2015 at 22:05, Ville Voutilainen wrote: > On 25 June 2015 at 19:12, Ville Voutilainen wrote: >> On 25 June 2015 at 19:06, Matthew Fioravante wrote: >>> If you have a type T that has deleted move/copy operations and you want to >>> store objects of this type in a vector you are forced to default construct >>> the elements use the vector::vector(size_t) constructor. After this you >>> can naturally not push_back(), insert(), reserve(), etc.. as all of those >>> operations may require moves. >>> >>> If we want to call a different constructor, or we don't have a default >>> constructor for T we are out of luck and cannot use vector. >>> >>> We need to modify the behavior inside of vector's constructor to customize >>> which constructor for T is actually called. The way to do this is with >>> functional programming, that is we pass in a lambda to the vector >>> constructor telling it how to construct each element. >>> >>> I presented an idea similar to this in a different thread for another array >>> type, but I think this idea could be applied to vector. >> >> This might be useful background: >> http://cplusplus.github.io/LWG/lwg-defects.html#704 >> >> At one time, Gabriel Dos Reis discussed relaxing some of the type requirements >> for vector, but I don't think either of us were able to materialize >> that discussion into >> a proposal. Both of us are fairly busy, so I cannot promise that >> either will be able >> to provide much assistance. Gabriel might have good suggestions. Maybe. > > Ah. Also see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4416.pdf. > That > proposal was rejected by LEWG, though. The discussion summary is at https://issues.isocpp.org/show_bug.cgi?id=87 -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. .