220 20962 article Path: news.gmane.org!not-for-mail From: Andrew Tomazos Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: auto return Date: Tue, 29 Sep 2015 06:10:15 +0200 Lines: 100 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c2b90cb970f00520dafd2a X-Trace: ger.gmane.org 1443499818 23110 80.91.229.3 (29 Sep 2015 04:10:18 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 29 Sep 2015 04:10:18 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBD5KHQXXWYPRBKE6VCYAKGQEELD7UQY@isocpp.org Tue Sep 29 06:10:18 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-la0-f69.google.com ([209.85.215.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZgmF7-0003Pj-PH for gclcip-std-proposals@m.gmane.org; Tue, 29 Sep 2015 06:10:17 +0200 Original-Received: by labnm6 with SMTP id nm6sf8415678lab.1 for ; Mon, 28 Sep 2015 21:10:17 -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: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=SU59jDJ8RTlaXXKkVWLA/Oc2H/qn3KmTy1LN3wDjQU0=; b=JqpQMalBn2feSJ7nlX21Lk2yuI5+2gTsHZ0XhaqNQiOgT6ga97DQgZdiRpA6BLXOn6 cE91IzZtD5+A1gh5llWnfpZ4n16xHPvNw6asKxfNlJGRzw7r+R46Y5P40e78RC1AX4f0 L1m0od4LF5cYYH/0BJIK4bqCS94frfzr55S/60mZzZwdeb2lwS8Hwqe166PORPNbwEmD 2KU2JGhIUgv4U8cf7GolVDoco0sHwdDooqMwUi2LzoNZ7cSwD43euhgJrqaLB6zPLa12 AZEW+gm/6QSTXBntuznqwnJFfZfFPaGIr5z6Uxu7MMKiE+eY/7Qu3K5Xzsf1HCjH8Ovd 3Snw== X-Gm-Message-State: ALoCoQmpGSgC5PGBF+YUvRNxho08edBjg2cGvvv92p7PB/7fCWFIzo7Xw/tmXbnpaWCfQSDF7LdN X-Received: by 10.180.160.146 with SMTP id xk18mr3434469wib.3.1443499816999; Mon, 28 Sep 2015 21:10:16 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.253.231 with SMTP id ad7ls666971wid.11.gmail; Mon, 28 Sep 2015 21:10:15 -0700 (PDT) X-Received: by 10.194.114.199 with SMTP id ji7mr24009218wjb.19.1443499815631; Mon, 28 Sep 2015 21:10:15 -0700 (PDT) Original-Received: from mail-wi0-x22d.google.com (mail-wi0-x22d.google.com. [2a00:1450:400c:c05::22d]) by mx.google.com with ESMTPS id qt4si26735396wic.79.2015.09.28.21.10.15 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Sep 2015 21:10:15 -0700 (PDT) Received-SPF: pass (google.com: domain of andrewtomazos@gmail.com designates 2a00:1450:400c:c05::22d as permitted sender) client-ip=2a00:1450:400c:c05::22d; Original-Received: by wicfx3 with SMTP id fx3so131462245wic.1 for ; Mon, 28 Sep 2015 21:10:15 -0700 (PDT) X-Received: by 10.180.10.197 with SMTP id k5mr20976331wib.22.1443499815299; Mon, 28 Sep 2015 21:10:15 -0700 (PDT) Original-Received: by 10.28.73.137 with HTTP; Mon, 28 Sep 2015 21:10:15 -0700 (PDT) X-Original-Sender: andrewtomazos@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of andrewtomazos@gmail.com designates 2a00:1450:400c:c05::22d as permitted sender) smtp.mailfrom=andrewtomazos@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:20962 Archived-At: --001a11c2b90cb970f00520dafd2a Content-Type: text/plain; charset=UTF-8 It is a common pattern to declare a local variable of the return type of the enclosing function, mutate it into the required result, and then return it... std::vector> build_points() { std::vector> result; while (c) result.emplace_back(g(c),h(c)); return result; } First, imagine we defined `auto return` as a kind of decl-specifier that implied these two things: 1. The declared variable has the return type of the enclosing function. 2. The variable is automatically returned when the function falls off the end: std::vector> build_points() { auto return result; while (c) result.emplace_back(g(c),h(c)); } Now suppose we said that this variable could be unnamed, and in such cases the keyword return could be used as an id-expression to refer to this return value: std::vector> build_points() { auto return; while (c) return.emplace_back(g(c),h(c)); } Now suppose we said that if the expression return appears in a function, the auto return declaration is created implicitly: std::vector> build_points() { while (c) return.emplace_back(g(c),h(c)); } Let me know if there is interest. -- --- 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/. --001a11c2b90cb970f00520dafd2a Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
It is a common pattern to declare a local variable of the = return type of the enclosing function, mutate it into the required result, = and then return it...

=C2=A0 std::vector<std::pa= ir<int,int>> build_points() {
=C2=A0 =C2=A0=C2=A0std::ve= ctor<std::pair<int,int>>=C2=A0result;
=C2=A0 =C2=A0 w= hile (c)=C2=A0result.emplace_back(g(c),h(c));
=C2=A0 =C2=A0 retur= n=C2=A0result;
=C2=A0 }

First,= imagine we defined `auto return` as a kind of decl-specifier that implied = these two things:

=C2=A0 1. The declared variable = has the return type of the enclosing function.
=C2=A0 2. The vari= able is automatically returned when the function falls off the end:

=C2=A0=C2=A0std::vector<std::pair<int,int>> b= uild_points()=C2=A0{
=C2=A0 =C2=A0 auto return=C2=A0result;
=
=C2=A0 =C2=A0 while (c)=C2=A0result.emplace_back(g(c),h(c));
=C2=A0 }

Now suppose we said that this variab= le could be unnamed, and in such cases the keyword return could be used as = an id-expression to refer to this return value:

=C2=A0 std::vector<std::pair<int,int>> build_points()=C2=A0{=
=C2=A0 =C2=A0 auto return;
=C2=A0 =C2=A0 while (c) ret= urn.emplace_back(g(c),h(c));
=C2=A0 }

Now suppose we said that if the expression return appears in a func= tion, the auto return declaration is created implicitly:

=C2=A0 std::vector<std::pair<int,int>> build_points= ()=C2=A0{
=C2=A0 =C2=A0 while (c) return.emplace_back(g(c),h(c));=
=C2=A0 }

Let me know if t= here is interest.

--

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