220 20917 <3a1c9a29-3c55-403c-9d94-1504eabc8e44@isocpp.org> article Path: news.gmane.org!not-for-mail From: Vincent Picaud Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Introducing the returntype keyword Date: Mon, 28 Sep 2015 06:01:56 -0700 (PDT) Lines: 118 Approved: news@gmane.org Message-ID: <3a1c9a29-3c55-403c-9d94-1504eabc8e44@isocpp.org> References: <24e315aa-2daf-4e47-933b-1f45157a0f79@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2223_1287738834.1443445317043" X-Trace: ger.gmane.org 1443445321 10728 80.91.229.3 (28 Sep 2015 13:02:01 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 28 Sep 2015 13:02:01 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDTIFJOFQUJBBRXUUSYAKGQE6Z2WROA@isocpp.org Mon Sep 28 15:02:01 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qg0-f72.google.com ([209.85.192.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZgY48-00005R-F5 for gclcip-std-proposals@m.gmane.org; Mon, 28 Sep 2015 15:02:00 +0200 Original-Received: by qgez77 with SMTP id z77sf185617094qge.2 for ; Mon, 28 Sep 2015 06:01:59 -0700 (PDT) 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 :content-type: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=DxDaXHR2xbK6DE1OemofdfVE4Po3hGkehwFhtdXxdlw=; b=EHh/QDn1QrWMhnIV9dXBMGGkJOklkAytGCTxlizF05XiYXTXEJ8UDRTBF9hiLKZMO0 IjEhMHhF2+vRAzGKrrLvniB7A8hTEkXProvNctMF0I9IddraBqSGHxtF6JUmaAA25bpt hzZSGf8sDp0cdP8yxhq9YWSfWITQNydeoXc1GlokbpGfV6xuH1D+TeRMcWMP/VFTzqML ang2wFvuHgKZ2r9tf1lmSC4iwQ4xY7H98UR0b414lCeF7rbOYoZ9iKVCqkx2etewIn2I 62ifnhfebNjcORu8PW0QwYCK81dItJcfNUkUxP3tCuEmAITBNOXgYjD9UsyYng6p2Lj/ jKVg== 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:content-type: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=DxDaXHR2xbK6DE1OemofdfVE4Po3hGkehwFhtdXxdlw=; b=PGco1aHVoMZcbsYFsBPjKN/njwqavDK1ut6oN3UWRojRe5GComOWOW/kJPRUoiWcaJ NHTC9peudbeVQ9d4fcOFkCXkyUQZuNbSGKqoNkYGMU16WbTzrZwTk+7q3O4eB6NO+8hE ylSbiv7tb5da3g4nfGIOgp+6EtloYL/aX1Au2G8v661pIud6jsvTcSV6ohPSNzDvdq7j zQVMqfU6K/WIKDmit/LoyyDQGz0pCiGYvYY9DTmm2n/PNxjNMjRVpUSVTOofVtwE4mnL tABwiWacDZlGUp37yxVU7JMP+AoMKUW2mgI7BdrIkQg3BIlnU9XI5y0lAPVhYm1rg/K8 lrKA== X-Gm-Message-State: ALoCoQm+NsYC5XwX76qbDTd0RwIAG8tAJ73cuBZRq0dYYrIv4zOrT+ZvOW6iMXmNlhhQ7zNZCXI1 X-Received: by 10.31.16.79 with SMTP id g76mr18201455vki.10.1443445319074; Mon, 28 Sep 2015 06:01:59 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.12.204 with SMTP id 73ls1708012iom.31.gmail; Mon, 28 Sep 2015 06:01:58 -0700 (PDT) X-Received: by 10.50.28.19 with SMTP id x19mr142179igg.16.1443445318090; Mon, 28 Sep 2015 06:01:58 -0700 (PDT) In-Reply-To: <24e315aa-2daf-4e47-933b-1f45157a0f79@isocpp.org> X-Original-Sender: picaud.vincent@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:20917 Archived-At: ------=_Part_2223_1287738834.1443445317043 Content-Type: multipart/alternative; boundary="----=_Part_2224_813007833.1443445317043" ------=_Part_2224_813007833.1443445317043 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable I do agree with Mikhail Semenov, a* returntype* keyword would be nice Note that: SomeType foo(SomeArgTypes... someArgs) { decltype(foo(someArgs)) toReturn; ..... return toReturn; } is only a partial and error prone solution, as you have to modify=20 "SomeArgs" two times: - function prototype - decltype(...) if you have to modify foo arguments. Le mercredi 23 septembre 2015 21:32:48 UTC+2, Mikhail Semenov a =C3=A9crit = : > > I propose to introduce the *returntype *keyword, which will represent the= =20 > return type of the current function. > > The aim is=20 > (1) to define a local variable, which will be used to return the value of= =20 > the function. > (2) to convert an expression to the value of the return type. > > In practice, it is convenient to use when you want to change the return= =20 > type without restructuring the whole function body. > > struct Type2 { explicit Type2(int){} }; > > Type2 f2_braces()=20 > { > returntype local2{2}; // ok > return local2; // > > ... > return returntype{10}; // ok > } > > If I want to change Type2 to Type3 I need only to change the function=20 > header without touching the body. > > > > --=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/. ------=_Part_2224_813007833.1443445317043 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I do agree with Mikhail Semenov= , a returntype keyword would be nice

Note that:
SomeType f= oo(SomeArgTypes... someArgs)
{
decltype(foo(someArgs)) toReturn;
.= ....
return toReturn;
}

is only a partial and error prone solut= ion, as you have to modify "SomeArgs" two times:
=C2=A0- funct= ion prototype
=C2=A0- decltype(...)
if you have to modify foo argumen= ts.

Le mercredi 23 septembre 2015 21:32:48 UTC+2, Mikhail Semenov a = =C3=A9crit=C2=A0:
I propose to introduce the returntype keyword, which will r= epresent the return type of the current function.

= The aim is
(1) to define a local variable, which will be used to= return the value of the function.
(2) to convert an expression t= o the value of the return type.

In practice, it is= convenient to use when you want to change the return type without restruct= uring the whole function body.

struct Type2 { expl= icit Type2(int){} };

Type2 f2_braces()
{=C2=A0=C2=A0=C2=A0 returntype local2{2}; // ok
=C2=A0=C2=A0=C2= =A0 return local2; //

=C2=A0=C2=A0=C2=A0 ...
= =C2=A0=C2=A0=C2=A0 return returntype{10}; // ok
}

If I want to change Type2 to Type3 I need only to change the function he= ader without touching the body.


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