220 18333 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Use cases for dyn_array Date: Mon, 1 Jun 2015 19:13:26 +0300 Lines: 37 Approved: news@gmane.org Message-ID: References: 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 1433175209 23157 80.91.229.3 (1 Jun 2015 16:13:29 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 1 Jun 2015 16:13:29 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBJ4JWKVQKGQEZMWG2QY@isocpp.org Mon Jun 01 18:13:29 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f198.google.com ([209.85.214.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YzSLA-0004lU-LA for gclcip-std-proposals@m.gmane.org; Mon, 01 Jun 2015 18:13:28 +0200 Original-Received: by obbnx5 with SMTP id nx5sf201347849obb.3 for ; Mon, 01 Jun 2015 09:13:27 -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:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=ZB+rByU8WMmal7oOKKtrbsUY46qq7NFY87vvgB2jfPc=; b=C4yKcz6xVd2DPooLcMu00xHJiY/2neMWtsd/Xx8ro4YBcmHriMNNLSSijrdIj8xyYB uPxn1vFb9LgSQmLr1yCKlNax1qRVHG6eidleGKX86lq7ItsimjeyERBJbDEVX2cVV5Ur 1GhCbgAwx/HTGB4609sSBKdk+syl2qIjx9xu4JJOjfU/jbdhYa8VGmJZjnOeLRTEZ4lG QjWFND1/3xCN60ovK49cYiX+6WIJegqY1JfflJBh9XSihS9TrPc8PQMujKLJ0b+MbgDc tekAu9iYSfIYGFCf6a2j1GnARaKDKwjVuuJeNSEuJ616zh5JhG5H9B7uaUXzz+oauiQB lRqw== X-Gm-Message-State: ALoCoQkXZL1ia+E7VHktOLD6GbOJkHoh2eAK7MZtrpXRvP/rFmO3XNRy5xdJ86B4AER1iWkpUiyA X-Received: by 10.43.126.71 with SMTP id gv7mr12726548icc.27.1433175207722; Mon, 01 Jun 2015 09:13:27 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.154.196 with SMTP id c187ls1359628ioe.101.gmail; Mon, 01 Jun 2015 09:13:26 -0700 (PDT) X-Received: by 10.50.111.131 with SMTP id ii3mr14354947igb.47.1433175206925; Mon, 01 Jun 2015 09:13:26 -0700 (PDT) Original-Received: from mail-ie0-x231.google.com (mail-ie0-x231.google.com. [2607:f8b0:4001:c03::231]) by mx.google.com with ESMTPS id b6si8656483ign.1.2015.06.01.09.13.26 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jun 2015 09:13:26 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4001:c03::231 as permitted sender) client-ip=2607:f8b0:4001:c03::231; Original-Received: by iesa3 with SMTP id a3so112875453ies.2 for ; Mon, 01 Jun 2015 09:13:26 -0700 (PDT) X-Received: by 10.107.166.203 with SMTP id p194mr15759088ioe.30.1433175206779; Mon, 01 Jun 2015 09:13:26 -0700 (PDT) Original-Received: by 10.36.152.8 with HTTP; Mon, 1 Jun 2015 09:13:26 -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:c03::231 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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:18333 Archived-At: On 1 June 2015 at 19:07, Matthew Fioravante wrote: > I know dyn_array was removed from the standard for now, but I have some uses > cases for a type like this. Specifically for a fixed size heap allocated > array. I don't much care whether or not its optimized to use stack memory. Then it's not dyn_array that you want. > > Specifically, a fixed size heap allocated array gives you the following > capabilities that std::vector does not. Note that these may or may not be > possible with the latest specification of dyn_array. > > 1) You can store a collection of non-copyable / non-movable types in a > contiguous memory block, improving cache locality. > 2) You can store const objects. This allows you to construct once and then > enforce invariants that the objects are never modified forever after. > 3) The container will always perform an exact size memory allocation for > you, unlike vector which may allocate more in anticipation of future > push_back() calls. > 4) The container only needs to store 2 pointers instead of 3, making objects > of this type much more cache line friendly. Any particular reason why you don't just use the array version of unique_ptr? > For this to work, first dyn_array should be move constructible from > dyn_array. The move constructor should also be implemented to just steal ...especially since unique_ptr for array types gives you this. -- --- 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/. .