220 11850 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: N4078: Rvalue reference overloads for value() method returns object by value Date: Fri, 11 Jul 2014 12:34:55 +0300 Lines: 53 Approved: news@gmane.org Message-ID: References: <4DA018C3-2327-4F55-B7F8-7988EC7B789A@gmail.com> <1a858a77-310b-4591-aaf5-960c40d9f5fc@isocpp.org> <66AF41C1-CB37-4311-98EA-D47DBC6068DC@gmail.com> <66c38b61-7a95-4ace-b34f-2346bb334fb9@isocpp.org> <6F4B3C72-9962-48DC-8527-0C89EA1B9710@gmail.com> <35873CE5-ED8C-4C03-A6A1-E4132DECD91F@gmail.com> <335948E6-8140-4673-B958-930356A52070@gmail.com> <76ACA175-5A44-4BE8-B49F-BAC6DA65E6B1@gmail.com> <4D3852AD-1AEB-44BA-941C-D645BAD19405@gmail.com> <6a4b6425-1167-40c1-acd8-3945c8cd4c74@isocpp.org> <13DD0D7A-A146-4667-9F30-6FB3739CDBE0@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1405071307 6242 80.91.229.3 (11 Jul 2014 09:35:07 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 11 Jul 2014 09:35:07 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRBQW772OQKGQEY6VEPDA@isocpp.org Fri Jul 11 11:35:00 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qg0-f70.google.com ([209.85.192.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1X5XEJ-00027b-Fm for gclcip-std-proposals@m.gmane.org; Fri, 11 Jul 2014 11:34:59 +0200 Original-Received: by mail-qg0-f70.google.com with SMTP id i50sf1844302qgf.1 for ; Fri, 11 Jul 2014 02:34:58 -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:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type:content-transfer-encoding; bh=iAk5fVDmybBm4tKQHTr6qmVGNWB/hF8+epBfAEdSjUc=; b=iR4LM+e4s6yNkA4nP++FXnFTsKdn5kFAuZui6gEE44nwwh6AF0IHjUUcCBXdJiDXrF XyVMOG3BREyDdoqEANVjXPZ4YXtIsdDWu5j0BxErdbtgrt3RiPvAvuCRozQ7wxrnyfvK NFU02/JUPP2uoUhijyf9pCd3OBNkQCK+2mIVwBAkPcOGmI6xh1A+g1TEWyTcGpJjKgjp FwMmLPqw4Z1BEQJYNVUcWuEIVkB8RFUYFjjLTKEe4NirrzKsXT0aHdCe+TUR6GR9QIC6 42XjTqh9UH/sAzxCFnLjdoH8HBvJ0TXoGRH0LXdul+3nLM+w+q/vpZKoJ8hsptYpXu5d wcaA== X-Gm-Message-State: ALoCoQk9/TgsZ0dEsoOzBA49pmpbw3KtVkhZJvVk2tRaoJqkIA2uBxju9eRqMK52CLLZzWiy5ig5 X-Received: by 10.236.209.97 with SMTP id r61mr5144527yho.33.1405071298719; Fri, 11 Jul 2014 02:34:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.80.55 with SMTP id b52ls337546qgd.16.gmail; Fri, 11 Jul 2014 02:34:55 -0700 (PDT) X-Received: by 10.58.155.38 with SMTP id vt6mr51260626veb.3.1405071295530; Fri, 11 Jul 2014 02:34:55 -0700 (PDT) Original-Received: from mail-vc0-x233.google.com (mail-vc0-x233.google.com [2607:f8b0:400c:c03::233]) by mx.google.com with ESMTPS id wr7si1215002vcb.15.2014.07.11.02.34.55 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 11 Jul 2014 02:34:55 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c03::233 as permitted sender) client-ip=2607:f8b0:400c:c03::233; Original-Received: by mail-vc0-f179.google.com with SMTP id id10so1511019vcb.38 for ; Fri, 11 Jul 2014 02:34:55 -0700 (PDT) X-Received: by 10.52.135.226 with SMTP id pv2mr42611707vdb.33.1405071295442; Fri, 11 Jul 2014 02:34:55 -0700 (PDT) Original-Received: by 10.220.188.73 with HTTP; Fri, 11 Jul 2014 02:34:55 -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:f8b0:400c:c03::233 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:11850 Archived-At: On 11 July 2014 12:29, David Krauss wrote: > On 2014=E2=80=9307=E2=80=9311, at 5:09 PM, Andrzej Krzemienski wrote: > 2014-07-11 11:02 GMT+02:00 David Krauss : >> >> As was discussed earlier, return-by-xvalue does not work with local >> universal references. Universal references are not just a cute thing tha= t >> trendy programmers like to sprinkle around, they provide a way for gener= ic >> code to bind a name to something which may or may not be a reference. > David, would it be possible to illustrate with an example what you mean > here? > > > template< typename container_handle > > void operate_on_fifth_thing( container_handle && ch ) { > // Save only the fifth element. We don=E2=80=99t need the rest; OK to= free those > resources. > auto && fifth_thing =3D=3D ( * std::forward< container_handle >( ch )= )[ 5 > ]; > > // This is illustrated as a function call, but there might as well be= a > loop here. > process_for_a_long_time( std::forward< decltype( thing ) >( fifth_thi= ng > ) ); > } > > I don=E2=80=99t think this is far-fetched at all, aside from presupposing > rvalue-overloaded operator* and operator[]. > > You generally might do the same things with a named object as with a > temporary. =E2=80=9CForwarding contexts=E2=80=9D don=E2=80=99t all end at= the semicolon. Why is that code using auto&&? --=20 ---=20 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 e= mail 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-proposa= ls/. .