220 5226 article Path: news.gmane.org!not-for-mail From: Richard Smith Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: brace-intialization and C++14 generalized lambda capture Date: Tue, 25 Jun 2013 17:20:57 -0700 Lines: 78 Approved: news@gmane.org Message-ID: References: <10c2a060-47cc-47bc-9114-c599c4986f4f@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1372206058 2733 80.91.229.3 (26 Jun 2013 00:20:58 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 26 Jun 2013 00:20:58 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDVNBJG4YAIBB2XHVCHAKGQE2MAXB4Q@isocpp.org Wed Jun 26 02:21:01 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f198.google.com ([209.85.220.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UrdTn-0006v0-Cp for gclcip-std-proposals@m.gmane.org; Wed, 26 Jun 2013 02:20:59 +0200 Original-Received: by mail-vc0-f198.google.com with SMTP id hf12sf1646572vcb.9 for ; Tue, 25 Jun 2013 17:20:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-google-group-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type :content-transfer-encoding; bh=t14ghUCZ7IKhPtZIT7bAvIpbcABMj8WEUP8UKysisb4=; b=uunWOzih/ydh1b6EiTQfqpArqTaSQCRonrs/fOSWD4YtY9LDMLRfzWFxDz2TSa2abQ kcLJl25nzXZ0fknMXpZQfsGd1LOuZ5p+pw8YjA9f9flng4GUUPuZW/a4R03OIi3lDEle d6XXpCw9iMrh3pukvMTeJTMVVths3EV9/h7CGe9oPmcqGqz44/B0FIIaW5ROs+hXAJ2x jjQZtg3bNqaAiCv4X4jc7eiy2t2esTiJ1TpCNakUlRATBSYGLfcAb4a5bVirbLCyguBz RTNXKlpdemrHRiDaI80z7C5bzcRylJO3BLnj3YqDUrjHuEUtAFSFrp67DivS/xLDl4Ip X-Received: by 10.224.86.200 with SMTP id t8mr1959313qal.0.1372206058544; Tue, 25 Jun 2013 17:20:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.108.74 with SMTP id hi10ls265159qeb.50.gmail; Tue, 25 Jun 2013 17:20:57 -0700 (PDT) X-Received: by 10.221.39.72 with SMTP id tl8mr833665vcb.29.1372206057890; Tue, 25 Jun 2013 17:20:57 -0700 (PDT) Original-Received: from mail-ve0-x236.google.com (mail-ve0-x236.google.com [2607:f8b0:400c:c01::236]) by mx.google.com with ESMTPS id am6si6982670ved.139.2013.06.25.17.20.57 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 25 Jun 2013 17:20:57 -0700 (PDT) Received-SPF: pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c01::236 as permitted sender) client-ip=2607:f8b0:400c:c01::236; Original-Received: by mail-ve0-f182.google.com with SMTP id ox1so10849030veb.27 for ; Tue, 25 Jun 2013 17:20:57 -0700 (PDT) X-Received: by 10.58.76.34 with SMTP id h2mr734283vew.93.1372206057765; Tue, 25 Jun 2013 17:20:57 -0700 (PDT) Original-Sender: metafoo@gmail.com Original-Received: by 10.58.125.73 with HTTP; Tue, 25 Jun 2013 17:20:57 -0700 (PDT) In-Reply-To: X-Original-Sender: richard@metafoo.co.uk X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c01::236 as permitted sender) smtp.mail=metafoo@gmail.com; dkim=pass header.i=@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:5226 Archived-At: On Tue, Jun 25, 2013 at 2:20 PM, Ville Voutilainen wrote: > On 25 June 2013 22:07, Richard Smith wrote: >> On Tue, Jun 25, 2013 at 11:44 AM, wrote: >> > The C++14 CD (N3690) at the paragraph $5.1.2/11, says: >> > For every init-capture a non-static data member named by the identifie= r >> > of >> > the init-capture is declared in >> > the closure type. This member is not a bit-field and not mutable. The >> > type >> > of that member corresponds to >> > the type of a hypothetical variable declaration of the form =93auto >> > init-capture ;=94, except that the variable >> > name (i.e., the identifier of the init-capture) is replaced by a uniqu= e >> > identifier. >> > >> > As I understand this means that the type of member x declared in lambd= a >> > capture as [x{std::move(uniq_ptr)}] () {} will be the same as would be >> > for >> > the expression auto x{std::move(unique_ptr)}. That means that type of = x >> > would be std::initializer_list> (assuming that ty= pe >> > of >> > unique_ptr is std::unique_ptr). in contrast the original prposal >> > contains of lambda example [ x { move(x) }, y =3D transform(y, z), foo= , >> > bar, >> > baz ] { ... }, which suggest that type of x would be >> > std::unique_ptr. >> > >> > I am understanding the wording correctly? If so was this change made o= n >> > purpose? >> >> We discussed this in core. We didn't want init-captures to behave >> differently from auto variable initialization, but there was a feeling >> that auto variable initialization from a braced-init-list should be >> fixed to not produce a std::initializer_list type here. We are >> expecting at least one national body comment requesting a fix for >> this, so there's a good chance that auto-deduction from initializer >> lists will change in the C++14 FDIS to not give an initializer_list >> type in the above case. > > > > There's also a paper about it at > http://open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3681.html > > Richard, if you want to help with the wording, that would be much > appreciated. > I can utilize such wording with or without attribution, depending on whet= her > you want to be a co-conspirator or an innocent bystander. ;) I'd be happy to help. You should also contact Jason Merrill; he was looking at wording changes for this, and they were briefly included in his drafting for DR1467/1490/1589/1631. The approach of that drafting made braced auto initialization deduce initializer_list only if there were multiple initializers in the braces. FWIW, I much prefer your wholesale removal of deduction of initializer_list. --=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/. .