220 11276 article Path: news.gmane.org!not-for-mail From: Sebastian Gesemann Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: return type sugar (orthogonal to auto foo() {} ) Date: Thu, 12 Jun 2014 16:10:47 +0200 Lines: 44 Approved: news@gmane.org Message-ID: References: <30a83c0d-00e6-462a-822e-a1789787ec05@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1402582257 3102 80.91.229.3 (12 Jun 2014 14:10:57 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 12 Jun 2014 14:10:57 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDO4ZQHJWIBRB2HJ42OAKGQENMKOUIA@isocpp.org Thu Jun 12 16:10:50 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f197.google.com ([209.85.214.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Wv5iL-0004bJ-BB for gclcip-std-proposals@m.gmane.org; Thu, 12 Jun 2014 16:10:49 +0200 Original-Received: by mail-ob0-f197.google.com with SMTP id uz6sf6199298obc.4 for ; Thu, 12 Jun 2014 07:10:48 -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:in-reply-to:references:date :message-id:subject:from: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=4Pojx8/zvyVDA9T0w5VasQYunWgJ6jBpo5JtCb7QoJQ=; b=gBLvfQpZdEkvWUXDDtLmD/NyB33P1rihPHgSRFiAFKojzUpkug/RIgVjMT8hUvkpN9 CaIemcfDWDIX6bkw0tyGyrat0JYyMtgSkn7Pru2/Rs78+kP1epbWuROdMA1D11rogle2 pDZvZJZvbcjFZlSVPZ7sQv4tNHVZsPK4YB1KAfgYtwF+3dmJqD9xSqQSfcGtnJWJr/1C xvJWRZRr4TlIAPQwM55QrMN0gHVqUCUMaQsfWj+vccpNNYvXCzWbGJxJq4jHyNRpysay p3dmNNsqFOuObuiqiZ/i+cdX3zlk1/BqTYCFhA4gSU1jJxnUPyiYWEV89wMSqgjxner2 IyKA== X-Gm-Message-State: ALoCoQlcFhHZ0St/tUyuJBozA75RFA+qaUQToH2T1QsP8/erZAfLsJVob0sBfogjvjKDXPgQaX2f X-Received: by 10.182.29.1 with SMTP id f1mr7263451obh.23.1402582248449; Thu, 12 Jun 2014 07:10:48 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.48.112 with SMTP id n103ls3064024qga.86.gmail; Thu, 12 Jun 2014 07:10:47 -0700 (PDT) X-Received: by 10.58.246.132 with SMTP id xw4mr45853320vec.2.1402582247821; Thu, 12 Jun 2014 07:10:47 -0700 (PDT) Original-Received: from mail-qa0-x22a.google.com (mail-qa0-x22a.google.com [2607:f8b0:400d:c00::22a]) by mx.google.com with ESMTPS id b4si1221024qaw.71.2014.06.12.07.10.47 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 12 Jun 2014 07:10:47 -0700 (PDT) Received-SPF: pass (google.com: domain of s.gesemann@gmail.com designates 2607:f8b0:400d:c00::22a as permitted sender) client-ip=2607:f8b0:400d:c00::22a; Original-Received: by mail-qa0-f42.google.com with SMTP id dc16so1739982qab.29 for ; Thu, 12 Jun 2014 07:10:47 -0700 (PDT) X-Received: by 10.224.63.145 with SMTP id b17mr6309957qai.38.1402582247695; Thu, 12 Jun 2014 07:10:47 -0700 (PDT) Original-Received: by 10.96.109.194 with HTTP; Thu, 12 Jun 2014 07:10:47 -0700 (PDT) In-Reply-To: <30a83c0d-00e6-462a-822e-a1789787ec05@isocpp.org> X-Original-Sender: s.gesemann@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of s.gesemann@gmail.com designates 2607:f8b0:400d:c00::22a as permitted sender) smtp.mail=s.gesemann@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:11276 Archived-At: On Thu, Jun 12, 2014 at 12:16 PM, walter1234 wrote: > Coming back to C++ from Rust, one thing begin to miss is the 2way type > inference: its a nice choice on their part, you write the types in the > signature, then the types in the body are inferred. > > But perhaps a significant amount of this use could be covered by having > sugar to access the declared return type of a function within its own body. > > imagine > > auto foo( args... )->decltype(....some expression based on args...) { > > return_type accumulator; // 'return_type' is a shortcut for > whatever this functions declared return type is.. > ... do stuff with accumulator... > > return accumulator. > } > > ways of doing that without a new keyword, perhaps 'decltype(return)' , any > other ideas.. > In some ways this would go beyond what rust currently does. (rust can't yet > use an expression for the return type, although making it generic often > works because of how the return types are inferred by callers) I'm not sure about the utility for such a short cut -- given the fact that in C++14 you can do something like this: // note: no trailing return type auto foo(int x, double y) { return x+y; } Compared to what you suggest, this is the other way around: The return type can be deduced from whatever the function returns. -- --- 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/. .