220 34287 article Path: news.gmane.org!.POSTED!not-for-mail From: Eyal Rozenberg Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Idea: Extension of structured bindings to definition of structs Date: Mon, 4 Sep 2017 16:16:35 +0200 Lines: 75 Approved: news@gmane.org Message-ID: References: <59dcbbbc-c536-4b7b-9c88-0638fb0cd58a@technion.ac.il> <7b9bf263-d3ca-42bf-aed6-4c7606782a28@isocpp.org> <1762295.OciJaA9sdk@tjmaciei-mobl1> <74349bfe-bb5a-a2ce-4142-5d46103d1d9f@technion.ac.il> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1504534624 15686 195.159.176.226 (4 Sep 2017 14:17:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 4 Sep 2017 14:17:04 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:56.0) Gecko/20100101 Thunderbird/56.0 To: std-proposals@isocpp.org, Nevin Liber Original-X-From: std-proposals+bncBDHKZN7LR4ARBTOAWXGQKGQE2YE4M3Q@isocpp.org Mon Sep 04 16:16:44 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wr0-f200.google.com ([209.85.128.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dosB5-00034E-PP for gclcip-std-proposals@m.gmane.org; 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[192.16.191.27]) by mx.google.com with ESMTPS id u12si7441603edk.405.2017.09.04.07.16.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Sep 2017 07:16:44 -0700 (PDT) Received-SPF: pass (google.com: domain of srs0=5sp6a=af=technion.ac.il=eyalroz@cwi.nl designates 192.16.191.27 as permitted sender) client-ip=192.16.191.27; Original-Received: from fester.cwi.nl (fester.cwi.nl [192.16.191.27]) by fester.cwi.nl (8.14.4/8.12.3) with ESMTP id v84EGf7X013762; Mon, 4 Sep 2017 16:16:41 +0200 Original-Received: from [192.168.2.1] (ip565d4370.direct-adsl.nl [86.93.67.112] (may be forged)) (authenticated bits=0) by fester.cwi.nl (8.14.4/8.12.3) with ESMTP id v84EGeDP013755 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Mon, 4 Sep 2017 16:16:41 +0200 In-Reply-To: Content-Language: en-US X-Original-Sender: eyalroz@technion.ac.il X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of srs0=5sp6a=af=technion.ac.il=eyalroz@cwi.nl designates 192.16.191.27 as permitted sender) smtp.mailfrom=SRS0=5SP6A=AF=technion.ac.il=eyalroz@cwi.nl 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:34287 Archived-At: I'm not actually suggesting a new way to create a type. The type is=20 created anyway if I write: struct { decltype(std::get<0>(get_car_parts())) engine; decltype(std::get<0>(get_car_parts())) dashboard; decltype(std::get<0>(get_car_parts())) stickshift; } car_parts =3D get_car_parts(); I'm just suggesting some syntactic sugar for that statement: struct { auto engine, dashboard, stickshift; } car_parts =3D get_car_parts(); A third alternative is not to create a type and write: auto [ car_engine, car_dashboard, car_stickshift ] =3D get_car_parts(); but I (we?) should frown upon this use of prefixes in identifiers. As Larry Evans suggest, this scenario occasionally happens, so we're not=20 talking about an esoteric use-case. Eyal On 8/30/17 5:16 PM, Nevin Liber wrote: > On Wed, Aug 30, 2017 at 2:59 AM, Eyal Rozenberg > wrote: >=20 > You would be using an unnamed struct for the same reason you use an > "unnamed type" for non-struct variables with auto. We write: >=20 > =C2=A0 auto x =3D expr; >=20 >=20 > Even though you don't spell it out, that type already has a name. =C2=A0a= uto=20 > doesn't create a new type. >=20 > You are proposing yet another syntax to create a new type.=C2=A0 As for i= ts=20 > use, about the only thing you can do with it is pass it to a template=20 > function (or equivalent).=C2=A0 That use seems fairly marginal.=C2=A0 You= need=20 > much better usage examples for motivation. > --=20 > =C2=A0Nevin ":-)" Liber=C2=A0 > =C2=A0+1-847-691-1404 >=20 > --=20 > You received this message because you are subscribed to the Google=20 > Groups "ISO C++ Standard - Future Proposals" group. > To unsubscribe from this group and stop receiving emails from it, send=20 > an email to std-proposals+unsubscribe@isocpp.org=20 > . > To post to this group, send email to std-proposals@isocpp.org=20 > . > To view this discussion on the web visit=20 > https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAGg_6%2BMPQ= TnqdWLQ1UV8jF173jDXYQQx-abwwNV3v3iknocJ%3DQ%40mail.gmail.com=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/f9ccebb4-6704-167c-5f1e-b0f58794a15d%40technion.= ac.il. .