220 29466 <582F2738.7040209@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: for...(T : t) // fold expression improvement Date: Fri, 18 Nov 2016 11:07:20 -0500 Lines: 38 Approved: news@gmane.org Message-ID: <582F2738.7040209@gmail.com> References: <7c87350a-7ac2-489b-b107-ea25a7bd6c74@isocpp.org> <110fecc1-a731-f6ad-fa8d-cfe2cb36faaa@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: blaine.gmane.org 1479485247 5243 195.159.176.226 (18 Nov 2016 16:07:27 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 18 Nov 2016 16:07:27 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBBPOOXTAQKGQEAETCZYI@isocpp.org Fri Nov 18 17:07:23 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f69.google.com ([74.125.83.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c7lhC-0000Ai-NQ for gclcip-std-proposals@m.gmane.org; Fri, 18 Nov 2016 17:07:22 +0100 Original-Received: by mail-pg0-f69.google.com with SMTP id y71sf259372455pgd.0 for ; Fri, 18 Nov 2016 08:07:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to: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=ZAYhcLiifFGoVLRuS3O5dF1rKELx02GPF4q4aGz/Xn8=; b=STOXxM5Jap7qSeQYZBlncZXUseCII9nlAZtNBf3OzB+/VsBHqlUcWGHPAHM6AqjdIg s66uyHo5yIl6hDMPqPUyEW1WluBg6Oz9JBSdlbarT3v0Ix/YMDrtkFWkRJHHtCOq885f OS+lxzWVCdFBeBQ+XcoQrIzoLJ/M7TX7Rkp8WIL4iPlouS0+wuVs5Vtp8qgb0rFWu4JT /Wuxev/jp1gmfr6qKTuQ7zSpdKEoZdS9pgoQt7YXnbr6XiDW7T12HbwrdQ4j+isnIOzJ wVr8jtounXSCsqZXmvWOVvvv6QVHDKdMefIjokzvZeT5gSVxE1sBWraQFG/PoYuIItkZ E3mA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to: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=ZAYhcLiifFGoVLRuS3O5dF1rKELx02GPF4q4aGz/Xn8=; b=XN+19P27f7fxZzHZbUNYSwAbL3EENcQWO94qDIiifUtYnqvtV3WLryYI8+qks7nNXW +owhTCqdQZ3lY61DOgcfjTxUKoQ4Nk58zrgCvRDV/T5VkAC2wb/0NkYEC2rThcJQuaei QsK3proFCflYdQ0pVDIsIERooNB+srXnC1pgzhzMu3Y8i/PLXO0J6GNzvi1jWrvNnHdV Sb00zP0U/p0MmugYk0T/g9kRBmVQvwrEfrbtHQY1f+Z7baB10pPEsEbTzv9F/ii5h/Y/ VQ0lxfioWl6b+liBEumkFktul14pK6UGV0TtyuhFyOF8cSw7dPOjvkOaylzbXhU2/ngg b8HA== X-Gm-Message-State: AKaTC03ADzALM/38/F98ugNaDWY2zrtrGDvj0nl3Mt96QocEKCnGW2wS4bNp/BUleECqzA== X-Received: by 10.99.126.11 with SMTP id z11mr101118pgc.79.1479485245941; Fri, 18 Nov 2016 08:07:25 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.29.137 with SMTP id y9ls6986901otd.39.gmail; Fri, 18 Nov 2016 08:07:25 -0800 (PST) X-Received: by 10.55.207.134 with SMTP id v6mr569126qkl.105.1479485245109; Fri, 18 Nov 2016 08:07:25 -0800 (PST) Original-Received: from mail-qk0-x22e.google.com (mail-qk0-x22e.google.com. [2607:f8b0:400d:c09::22e]) by mx.google.com with ESMTPS id z47si2578565qtb.204.2016.11.18.08.07.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Nov 2016 08:07:25 -0800 (PST) Received-SPF: pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:400d:c09::22e as permitted sender) client-ip=2607:f8b0:400d:c09::22e; Original-Received: by mail-qk0-x22e.google.com with SMTP id q130so269071014qke.1 for ; Fri, 18 Nov 2016 08:07:25 -0800 (PST) X-Received: by 10.55.16.10 with SMTP id a10mr558228qkh.66.1479485244661; Fri, 18 Nov 2016 08:07:24 -0800 (PST) Original-Received: from [192.168.1.173] (tripoint.kitware.com. [66.194.253.20]) by smtp.googlemail.com with ESMTPSA id q21sm4351152qkq.8.2016.11.18.08.07.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Nov 2016 08:07:21 -0800 (PST) In-Reply-To: X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:400d:c09::22e as permitted sender) smtp.mailfrom=mwoehlke.floss@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:29466 Archived-At: On 2016-11-18 03:36, Ville Voutilainen wrote: > Alternatively, fold over a lambda: > > template > void foo(T... a) { > ([&]() { > std::cout << a << std::endl; > }(),...); > } Wow... that's twisty :-). I didn't know you could do that with fold expressions! (That... actually creates a *different lambda* for each item in `a`!) > Caveat emptor, it doesn't work with gcc or msvc yet. This version should work: template void foo(T... a) { ([&](auto&& ai) { std::cout << ai << std::endl; }(a),...); } ....and is less surprising that it does ;-). Instead of folding on the lambda itself, this version folds on invocation of the lambda (albeit a templated lambda). -- Matthew -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/582F2738.7040209%40gmail.com. .