220 11299 <92baab38-23fd-46f3-9e68-b894c9a0f07b@isocpp.org> article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Andrzej_Krzemie=C5=84ski?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: return type sugar (orthogonal to auto foo() {} ) Date: Fri, 13 Jun 2014 09:25:37 -0700 (PDT) Lines: 134 Approved: news@gmane.org Message-ID: <92baab38-23fd-46f3-9e68-b894c9a0f07b@isocpp.org> References: <30a83c0d-00e6-462a-822e-a1789787ec05@isocpp.org> <1cf79c47-8a07-4e41-b96b-465b01e044fa@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_297_30792517.1402676738095" X-Trace: ger.gmane.org 1402676752 22549 80.91.229.3 (13 Jun 2014 16:25:52 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 13 Jun 2014 16:25:52 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBA6M5SOAKGQEPZEKAPQ@isocpp.org Fri Jun 13 18:25:44 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qc0-f199.google.com ([209.85.216.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WvUIP-0007qi-0i for gclcip-std-proposals@m.gmane.org; Fri, 13 Jun 2014 18:25:41 +0200 Original-Received: by mail-qc0-f199.google.com with SMTP id l6sf1575472qcy.6 for ; Fri, 13 Jun 2014 09:25:40 -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 :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=TLGX4iWdB8da1XeDpxsykPiAj1CFigiOFRrLUxuaiAE=; b=oPOMZBjpUzBoSoIzuGIC2SDcMg54jJGhwieZhD3NqPJgLevE9X8sYn8SPfxs4fgUEd 650lzZmsg2JBS86aYWn0jHoHFuLeZ8Yzt61jNDtRc/MhF/CHVRFASXlFkForSeoqZiVI wO384d3csXfNz6e9VoTQ7tNbbrerB9p8S29+9fuCnniFOs6QxSTrDN2DYQ+Prx8G3YUQ MGM/gbivrjDd+28g8Hfrsfru4Ef7uUn1gzPmzoweARpFCJcm7Fmt05bBGAGR8PMlGlV8 eeYgRH5b9mZoDiHbLt8KYnU8YX5F5sCFoTCPdP0zxfvWGhU+RmNh/atiXJaqSP1twml/ tW/g== 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:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=TLGX4iWdB8da1XeDpxsykPiAj1CFigiOFRrLUxuaiAE=; b=ZhyJpx5qdfHX7CMBZ+nAF3t/PFqMzUJRMhQJsQihu8J9vxvaP6b58Gt5guwmQeHvAV ytsjoAL/3n4r168updEZKWBimEek2w92SN7okFvSGrkxofSivvfQBCZjnbbDBPL/lFsG cP28m1kSAvWhRf3EpBabpK4h965ctK4dU1kmAGXa2tPEcv5HCWTfuJKu2VyVRSRNuZGe s2HutUB+neJTvOolYrwdb6kXTlsJ5vS5zXpCDybJV6AyCX7ut6tjReYjm71vmD9KLNq7 HK9owdYECKd1ReqpL+3JzdT+xOf2hNl6aHITUW5KWjn5+NYJz8KEPDGQinDCK558/C0I Ni5A== X-Gm-Message-State: ALoCoQkcyi8cs5VrPH1XFOIHCQ5GOiEFWkorJFSpVXaKCiQ0RTPoH8ATYQ+PtDsUYY997R3v0XdW X-Received: by 10.58.151.201 with SMTP id us9mr511785veb.23.1402676740213; Fri, 13 Jun 2014 09:25:40 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.87.38 with SMTP id q35ls1014650qgd.98.gmail; Fri, 13 Jun 2014 09:25:39 -0700 (PDT) X-Received: by 10.140.44.75 with SMTP id f69mr50899qga.11.1402676739413; Fri, 13 Jun 2014 09:25:39 -0700 (PDT) In-Reply-To: <1cf79c47-8a07-4e41-b96b-465b01e044fa@isocpp.org> X-Original-Sender: akrzemi1@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:11299 Archived-At: ------=_Part_297_30792517.1402676738095 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable W dniu pi=C4=85tek, 13 czerwca 2014 18:24:28 UTC+2 u=C5=BCytkownik Andrzej= =20 Krzemie=C5=84ski napisa=C5=82: > > > W dniu czwartek, 12 czerwca 2014 12:16:04 UTC+2 u=C5=BCytkownik walter123= 4=20 > napisa=C5=82: >> >> Coming back to C++ from Rust, one thing begin to miss is the 2way type= =20 >> inference: its a nice choice on their part, you write the types in the= =20 >> signature, then the types in the body are inferred. >> >> But perhaps a significant amount of this use could be covered by having= =20 >> sugar to access the declared return type of a function within its own bo= dy. >> >> imagine >> >> auto foo( args... )->decltype(....some expression based on args...) { >> >> return_type accumulator; // 'return_type' is a shortcut for= =20 >> whatever this functions declared return type is.. >> ... do stuff with accumulator... >> >> return accumulator. >> } >> >> ways of doing that without a new keyword, perhaps 'decltype(return)' ,= =20 >> any other ideas.. >> In some ways this would go beyond what rust currently does. (rust can't= =20 >> yet use an expression for the return type, although making it generic of= ten=20 >> works because of how the return types are inferred by callers) >> > =20 > How about doing it the Go style: > =20 > auto foo( args... ) -> decltype(....some expression based on args...)= =20 > accumulator > { =20 > do_stuff_with(accumulator); > return accumulator. > } > =20 Or even w/o return statement because it is obvious what we return: =20 auto foo( args... ) -> decltype(....some expression based on args...)=20 accumulator {=20 do_stuff_with(accumulator); // no return (and no UB) } --=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_297_30792517.1402676738095 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

W dniu pi=C4=85tek, 13 czerwca 2014 18:24:28 UTC+2 u= =C5=BCytkownik Andrzej Krzemie=C5=84ski napisa=C5=82:

W dniu czwartek, 12 czerwca 2014 12:16:04 UTC+2= u=C5=BCytkownik walter1234 napisa=C5=82:
Coming back to C++ from Rust, one thing begin to miss is the 2w= ay 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 sug= ar to access the declared return type of a function within its own body.

imagine

auto foo(  arg= s...  )->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 accumulat= or...

     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)
&nb= sp;
How about doing it the Go style:
 
a= uto foo(  args...  ) -> decltype(....some expression based on = args...) accumulator
{   
  do_stuff_with(accumul= ator);
  return accumulator.
}
&nbs= p;
Or even w/o return statement because it is obvious what we ret= urn:
 
auto foo( args... ) -> decltype(....so= me expression based on args...) accumulator
{
   do_stu= ff_with(accumulator);
   // no return (and no UB)
}

--

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