220 10180 <9905A61B-89E1-4F7E-BD12-D5815A951FCC@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::conditional pick() function? Date: Sat, 5 Apr 2014 14:18:41 +0800 Lines: 60 Approved: news@gmane.org Message-ID: <9905A61B-89E1-4F7E-BD12-D5815A951FCC@gmail.com> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 7.2 \(1874\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_DB776959-7D28-4363-9555-2E47E7A27221" X-Trace: ger.gmane.org 1396678808 5044 80.91.229.3 (5 Apr 2014 06:20:08 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 5 Apr 2014 06:20:08 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBDWB72MQKGQEH7M4EDQ@isocpp.org Sat Apr 05 08:20:01 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f199.google.com ([209.85.192.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WWJxQ-0003yi-Va for gclcip-std-proposals@m.gmane.org; Sat, 05 Apr 2014 08:20:01 +0200 Original-Received: by mail-pd0-f199.google.com with SMTP id x10sf14448785pdj.6 for ; Fri, 04 Apr 2014 23:19:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:message-id:mime-version:subject:date :references:to:in-reply-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; bh=7xcS1Dz9bFUvjGrclx1NUZC3Bs6heTg2pa1TaqWEeZE=; b=fhzlcIeuLwbuYfhVJkUUgtjQQsPyWfctSGuq7/zG3zbEdW9UFEttVHhZMRChFfPqVA Bqe/J49CFDn0Fr1N6GQP4jIW3en2l9T9liLeBg0gWFXd5dvIDk1r8i0oU1+VASmEdhXV Owv6EgHe4+vBbBGJYWtMhGlwHxlN4K66scUabO7lON8aIvJXq9NxnJhTXfNl/9WtzhX8 9b8h+rVm6MCHfsdPefVxEFsqlIPsb2TTeChz4a1HW7QuR7FUdSEFyAZ4s2gA/Vd6kCDP CeQwbNUt/wxW0/KaF52yHkDdKTRM8jKGTKNZaHYXEiBfQBD98FoHHKJOoxRyMpVCgtCe t4QA== X-Gm-Message-State: ALoCoQngrRPhC2wAl0BrEejca7TC4j8Zh9HHzrUABvtcBEoxGfGgajEXPzUjmmhSluv5ako6fc7t X-Received: by 10.66.122.69 with SMTP id lq5mr7201376pab.17.1396678799516; Fri, 04 Apr 2014 23:19:59 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.57.104 with SMTP id h8ls941905igq.0.gmail; Fri, 04 Apr 2014 23:19:58 -0700 (PDT) X-Received: by 10.69.2.2 with SMTP id bk2mr19143900pbd.75.1396678798348; Fri, 04 Apr 2014 23:19:58 -0700 (PDT) Original-Received: from mail-pa0-x236.google.com (mail-pa0-x236.google.com [2607:f8b0:400e:c03::236]) by mx.google.com with ESMTPS id my2si5493726pbc.197.2014.04.04.23.19.58 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 04 Apr 2014 23:19:58 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::236 as permitted sender) client-ip=2607:f8b0:400e:c03::236; Original-Received: by mail-pa0-f54.google.com with SMTP id lf10so4412885pab.13 for ; Fri, 04 Apr 2014 23:19:58 -0700 (PDT) X-Received: by 10.68.237.38 with SMTP id uz6mr19218139pbc.72.1396678798197; Fri, 04 Apr 2014 23:19:58 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.150]) by mx.google.com with ESMTPSA id it4sm21992397pbd.48.2014.04.04.23.19.40 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 04 Apr 2014 23:19:57 -0700 (PDT) In-Reply-To: X-Mailer: Apple Mail (2.1874) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::236 as permitted sender) smtp.mail=potswa@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:10180 Archived-At: --Apple-Mail=_DB776959-7D28-4363-9555-2E47E7A27221 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=ISO-8859-1 This sounds an awful lot like a C11 type-generic expression. A TGE uses the= type of an unevaluated controlling expression to select among several sube= xpressions. The type and value of the TGE are those of the selected subexpr= ession; the other subexpressions are not evaluated. TGEs do more than std::conditional can do, but less than the proposed stati= c_if. I think they just might be an appropriate solution. - D --=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/. --Apple-Mail=_DB776959-7D28-4363-9555-2E47E7A27221 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1 This sounds an awful lot= like a C11 type-generic expression. A TGE uses the type of an unevaluated = controlling expression to select among several subexpressions. The type and= value of the TGE are those of the selected subexpression; the other subexp= ressions are not evaluated.

TGEs do more than std::conditional can do, but less than the proposed&nbs= p;static_if. I think they just might be an ap= propriate solution.

- D

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