220 29535 <108e091f-526e-47b9-b8c9-3c77452a965d@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Marc Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: decltype(return) Date: Thu, 24 Nov 2016 14:26:14 -0800 (PST) Lines: 76 Approved: news@gmane.org Message-ID: <108e091f-526e-47b9-b8c9-3c77452a965d@isocpp.org> References: <658f00ff-7a02-7c04-3fcb-6ac7f45b777b@scylladb.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_8086_1923413685.1480026374631" X-Trace: blaine.gmane.org 1480026378 16097 195.159.176.226 (24 Nov 2016 22:26:18 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 24 Nov 2016 22:26:18 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCGJRE7HX4IBBB6S3XAQKGQEU27FOUY@isocpp.org Thu Nov 24 23:26:13 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f70.google.com ([74.125.83.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cA2T6-0003Aa-M1 for gclcip-std-proposals@m.gmane.org; Thu, 24 Nov 2016 23:26:12 +0100 Original-Received: by mail-pg0-f70.google.com with SMTP id g186sf132219356pgc.2 for ; Thu, 24 Nov 2016 14:26:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=QevP10DRF/RRg9pFCgBLbCAmxRvQBXb4gIKXiduAEd8=; b=ftSYreM8mnczYAQ7jchjWwmQZpoLbIoL3nlSU4uGycVG9v2MLyKljCgZb34VY2dMAZ a15bQrHYvlMqmjMEevRMDIpC5OjlgYCZ8E9XgiXgfduG70+XcHSMGpDRSSscue9BmrX9 ZSA34TqDV1VJZk9LHBe8tL7nsG5VvqfcETSFK26duhRODDzKuD+Wts9qJSIGHVAqfr4b FhHLdbPEv+xKwM8lCK0Je/wdlmXn9RMg0Jkq0CH8VGsdzkWknjP7JEc2TZCjwDhPon2F 6xN3+QpSW+wfofuP/imjR3WLUKx0Gh6hR4u1FudlLgQvmVIVFJ3saCSWHc1ci+R6T63T R3tw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=QevP10DRF/RRg9pFCgBLbCAmxRvQBXb4gIKXiduAEd8=; b=xOPwH6KN/D8P73Ivwf5iRPgjtU7CzB7BsIQXfxGdWJ4LD7uFFKN9v/3FUzj+gnXiyf rY7H9jDMkMK/bNlJ6n2Xg4Uxnxqpl2O4V6+qUeYXTnQrcBPSLle7+2FPCg7YZI7kCLTZ 5f/MkPW9xN/nYeAQRAw1utMgXaD5ey9z5RNwtCVq/Ynz2ze4EkGoPKOb+2kjL1xXHvjb auC1gbavcJIKEPEMm0EF/3N30NLf5YEcfJGlJucD8q7koEegfcGxPE0uvk1/FHr7jrtY IV/5f6MrReRxN0OYBCS0BWD7gKNIOrUxid8+2VZ/zHI3MZRD7XQuWwxByFqvg3yA+Ibg 6+NQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=QevP10DRF/RRg9pFCgBLbCAmxRvQBXb4gIKXiduAEd8=; b=ldX9QdPwv+oE79R8L038EzmsKGuZva83I3cY/1YFZDvl1blzF/Hs+QSyCLO128JEQb N0CyGUxtJCq+ii+9IKuSItm/a3SEwmPUgg4lFNUmRZ435QG8TZnYb80tofVAdk5TgJy4 oeIHOfAaWrQA8Qb3yfhAj+yXwTMVNRBr2aCsA1Jdz/6cZxI/KTmaWjVcR0unLumJgdof AtpZeZdPDVCglu5vN5yVnHDAS4+W9gsfZ3vITe1HrLLdDdr3csOvUhC/2WPgPwFLQ0LD IXTvcIvK9paTq8uS9bElttkbTIu3T8tAfOSMxH/xGPida+icuYNSEdKUf3f4phwtNAEN WBMA== X-Gm-Message-State: AKaTC01WxIM0Hmf+A1naLUjoT0GwVVddywjwApTWDYvm3amqq4xy9wUCmbSa4CMifIg3mg== X-Received: by 10.99.7.194 with SMTP id 185mr1994476pgh.6.1480026375947; Thu, 24 Nov 2016 14:26:15 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.26.102 with SMTP id u35ls4266040otu.4.gmail; Thu, 24 Nov 2016 14:26:15 -0800 (PST) X-Received: by 10.157.44.172 with SMTP id p41mr133658otb.6.1480026375051; Thu, 24 Nov 2016 14:26:15 -0800 (PST) In-Reply-To: <658f00ff-7a02-7c04-3fcb-6ac7f45b777b@scylladb.com> X-Original-Sender: marc.glisse@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:29535 Archived-At: ------=_Part_8086_1923413685.1480026374631 Content-Type: multipart/alternative; boundary="----=_Part_8087_1327853358.1480026374631" ------=_Part_8087_1327853358.1480026374631 Content-Type: text/plain; charset=UTF-8 On Friday, November 18, 2016 at 5:01:41 PM UTC+1, Avi Kivity wrote: > > > map, baz> > complicated(...) { > decltype(return) ret; > // add stuff to ret > return try; > } > > Instead of repeating the complicated type, refer to it via > decltype(return). Won't work with deduced return types, of course. > This has been suggested informally several times already, but afaik nobody did the work to write a paper and present it. For instance: https://groups.google.com/a/isocpp.org/d/topic/std-proposals/wdX31-nWSnc/discussion (it also appears in the discussions about allowing explicit constructors in return statements) -- 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/108e091f-526e-47b9-b8c9-3c77452a965d%40isocpp.org. ------=_Part_8087_1327853358.1480026374631 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Friday, November 18, 2016 at 5:01:41 PM UTC+1, Avi Kivi= ty wrote:

map<foo, map<set<bar>, baz>
complicated(...) {
=C2=A0 =C2=A0 =C2=A0decltype(return) ret;
=C2=A0 =C2=A0 =C2=A0// add stuff to ret
=C2=A0 =C2=A0 =C2=A0return try;
}

Instead of repeating the complicated type, refer to it via=20
decltype(return). =C2=A0Won't work with deduced return types, of co= urse.

This has been suggested informally several t= imes already, but afaik nobody did the work to write a paper and present it= ..
For instance:
https://groups.google.com/a/isocpp.org/d/topic/std-pr= oposals/wdX31-nWSnc/discussion
(it also appears in the discussions about= allowing explicit constructors in return statements)

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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/108e091f-526e-47b9-b8c9-3c77452a965d= %40isocpp.org.
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