220 21754 article Path: news.gmane.org!not-for-mail From: Sam Kellett Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Introducing the returntype keyword Date: Wed, 14 Oct 2015 08:27:14 +0100 Lines: 115 Approved: news@gmane.org Message-ID: References: <24e315aa-2daf-4e47-933b-1f45157a0f79@isocpp.org> <0884ab8b-672b-459a-9143-f522ea7ebf1d@isocpp.org> <3374ec49-e50e-40dc-8936-46e642a93ebf@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c3bfeece019305220b7db9 X-Trace: ger.gmane.org 1444807641 2216 80.91.229.3 (14 Oct 2015 07:27:21 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 14 Oct 2015 07:27:21 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDY6DWXBQIPRBU4H7CYAKGQE22DXONY@isocpp.org Wed Oct 14 09:27:21 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lb0-f200.google.com ([209.85.217.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZmGSy-0006Ad-Br for gclcip-std-proposals@m.gmane.org; Wed, 14 Oct 2015 09:27:16 +0200 Original-Received: by lbcao8 with SMTP id ao8sf20920583lbc.1 for ; Wed, 14 Oct 2015 00:27:15 -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: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=qrV+yYtXkqNkCE1kDzhQJNj2BZrJin3zKaACCuurEnU=; b=CKtdaZ/1i613DX4lOQYG2xER3GC/rshUFA60OWEvZpl8nswWzN7svN/s74w7Gxh3PW YXOYy2pguQPwmvLWLzZSfGvCKVdkoK6iU2Z+AB+Lvr3Y15Pu9aSOL4bj+Ly/x3/fBf3v gUMBAAm07+HpWaY6JLPfDpPkfSKSXhbJmI1JAdCGINjLzJQ1CmVGAVxAxDC+wr5vETKE nwCId5MbelkOmmqAXf+bVmIGIhZ51mK1K2ONoUoFISHyzoP+YXYdnfmPAdEF11m0kMoo Twbdvd9xvoqlTsNOG10jCXkBt1cbd9euuLdu3Yzm9bR7DZ3ODjLWmtJHRE+nUs3GVpoh hwDA== X-Gm-Message-State: ALoCoQnbz2RNfXlLmm9F6pwsIP92gsMCKA2lxBJHV/ZBHy98yFu8Tmzk9VDB0Z+YJ3uTox4kV54O X-Received: by 10.180.10.135 with SMTP id i7mr482680wib.2.1444807635894; Wed, 14 Oct 2015 00:27:15 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.25.32.207 with SMTP id g198ls5419lfg.18.gmail; Wed, 14 Oct 2015 00:27:14 -0700 (PDT) X-Received: by 10.112.154.9 with SMTP id vk9mr762347lbb.42.1444807634449; Wed, 14 Oct 2015 00:27:14 -0700 (PDT) Original-Received: from mail-lb0-x22a.google.com (mail-lb0-x22a.google.com. [2a00:1450:4010:c04::22a]) by mx.google.com with ESMTPS id h21si4685837lfb.104.2015.10.14.00.27.14 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Oct 2015 00:27:14 -0700 (PDT) Received-SPF: pass (google.com: domain of samkellett@gmail.com designates 2a00:1450:4010:c04::22a as permitted sender) client-ip=2a00:1450:4010:c04::22a; Original-Received: by lbcao8 with SMTP id ao8so39778954lbc.3 for ; Wed, 14 Oct 2015 00:27:14 -0700 (PDT) X-Received: by 10.112.17.105 with SMTP id n9mr775894lbd.78.1444807634188; Wed, 14 Oct 2015 00:27:14 -0700 (PDT) Original-Received: by 10.114.173.114 with HTTP; Wed, 14 Oct 2015 00:27:14 -0700 (PDT) In-Reply-To: X-Original-Sender: samkellett@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of samkellett@gmail.com designates 2a00:1450:4010:c04::22a as permitted sender) smtp.mailfrom=samkellett@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:21754 Archived-At: --001a11c3bfeece019305220b7db9 Content-Type: text/plain; charset=UTF-8 On 14 October 2015 at 06:03, Klemens Morgenstern < klemens.morgenstern@gmx.net> wrote: > Basically, there are various reasons why repeating the function >> signature is less than desirable. >> > > Well I am doubting that this is convincing, however there might be > situations where you need it for ambiguity reasons: > > > double foo(const bar & f) > { > return 34.1; > } > > > int foo(bar && b) > { > decltype(foo(b)) x; //type == double, because b binds to const > bar & inside the function > decltype(return) y; //type == int > return 42; > } > > > But I can't really come up with a good example where this is needed. Maybe > someone else has an idea. > what about when the return type is the result of some complex metaprogramming calculation? -- --- 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/. --001a11c3bfeece019305220b7db9 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On 14 October 2015 at 06:03, Klemens Morgenstern <= klemens.mo= rgenstern@gmx.net> wrote:
<= div dir=3D"ltr">
Ba= sically, there are various reasons why repeating the function
signature is less than desirable.

Well I am doubting that this is= convincing, however there might be situations where you need it for ambigu= ity reasons:


double foo(const bar & f)
{
=C2=A0 =C2=A0 =C2=A0 return 34.1;<= span style=3D"color:#000">
}


int foo(bar &&a= mp; b)<= /span>
{
=C2=A0 =C2=A0 =C2=A0 =C2=A0 decltype(foo(b)) x; //type =3D=3D double, becau= se b binds to const bar & =C2=A0inside the function
=C2=A0 =C2=A0 =C2=A0 =C2=A0 decltype(return) y; //type =3D=3D int
=C2=A0 =C2=A0 =C2=A0 =C2=A0 return 42;
}


But I can't really come up with a good example wher= e this is needed. Maybe someone else has an idea.
<= div>
what about when the return type is the result of some co= mplex metaprogramming calculation?

--

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