220 18783 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 19:12:26 +0300 Lines: 36 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 1435248755 19937 80.91.229.3 (25 Jun 2015 16:12:35 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 25 Jun 2015 16:12:35 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRB2WQWCWAKGQE66LC42I@isocpp.org Thu Jun 25 18:12:31 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f197.google.com ([209.85.213.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Z89lM-0007Gm-C2 for gclcip-std-proposals@m.gmane.org; Thu, 25 Jun 2015 18:12:28 +0200 Original-Received: by igczg2 with SMTP id zg2sf137532783igc.3 for ; Thu, 25 Jun 2015 09:12:27 -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=N3bO6mXyaTqqL9SCN4ZYOSQO3mtob9SEWECWPIZqm9U=; b=DiOdyHVUzMth/ClAqGa0BTvzGeBj3pJ4gh1AzO02+MCke6MrGErcnboWINRIaR6+NC n1y8FELiAgmZlkxaAGrVSWLFEQMvTWqyw9Eik9DvskFoD8FW2sUqrVQl/7IByAFL1Oie 9grM+0VI1lmgVpTq7wxPvHhsL9Toom6Y3X1tQYNkYjJZSZKKbCyKiGVmh329K30dGSUy sjivQYUZD6IgQJgAW06+bY64qW1lFqizSo51uvb3Ilnsd3Qwu9770fsOR2pJ8yU+Ryef us+0Y03d/kIZm6aPbxbVh6BoqzU/puev6L0779+QpUY08brIZrREXGkyBZoZ+Z3jNQtm EIQw== X-Gm-Message-State: ALoCoQkUxmuN4rwH9Nu6kPxCHpDaNwcJ776ENxjXewQB16GoFTHKOi61p03nKG92VjstQ/faPrWS X-Received: by 10.50.128.40 with SMTP id nl8mr4697113igb.4.1435248747284; Thu, 25 Jun 2015 09:12:27 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.129.65 with SMTP id nu1ls998564igb.40.gmail; Thu, 25 Jun 2015 09:12:26 -0700 (PDT) X-Received: by 10.107.9.150 with SMTP id 22mr42864396ioj.39.1435248746251; Thu, 25 Jun 2015 09:12:26 -0700 (PDT) Original-Received: from mail-ie0-x22e.google.com (mail-ie0-x22e.google.com. [2607:f8b0:4001:c03::22e]) by mx.google.com with ESMTPS id xd13si19982637icb.36.2015.06.25.09.12.26 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jun 2015 09:12:26 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4001:c03::22e as permitted sender) client-ip=2607:f8b0:4001:c03::22e; Original-Received: by iebrt9 with SMTP id rt9so57838523ieb.2 for ; Thu, 25 Jun 2015 09:12:26 -0700 (PDT) X-Received: by 10.43.8.4 with SMTP id oq4mr42857584icb.64.1435248746112; Thu, 25 Jun 2015 09:12:26 -0700 (PDT) Original-Received: by 10.36.152.7 with HTTP; Thu, 25 Jun 2015 09:12:26 -0700 (PDT) In-Reply-To: <06317928-6af2-4133-a38e-8d6c829f311b@isocpp.org> 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:c03::22e 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:18783 Archived-At: 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. -- --- 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/. .