220 11298 <1cf79c47-8a07-4e41-b96b-465b01e044fa@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 09:24:27 -0700 (PDT) Lines: 107 Approved: news@gmane.org Message-ID: <1cf79c47-8a07-4e41-b96b-465b01e044fa@isocpp.org> 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: multipart/alternative; boundary="----=_Part_317_24531460.1402676667554" X-Trace: ger.gmane.org 1402676683 21591 80.91.229.3 (13 Jun 2014 16:24:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 13 Jun 2014 16:24:43 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBPOL5SOAKGQE6Q3WLBY@isocpp.org Fri Jun 13 18:24:36 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f197.google.com ([209.85.220.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WvUHH-0006pi-Gv for gclcip-std-proposals@m.gmane.org; Fri, 13 Jun 2014 18:24:31 +0200 Original-Received: by mail-vc0-f197.google.com with SMTP id il7sf8320010vcb.0 for ; Fri, 13 Jun 2014 09:24:30 -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=1zOX9yPoF+2HZpqK6MIH+/PXRsbN5do6/PpWEHqP4fY=; b=S8haiG0QKZFAj+j5ts2D26v19OtiGPv60RfuowaVGFPzdUbFidXcIcBWKX/2c/vk2J pT6xIXkKlBM206tMisyZokvJc+2yOG+3l1b8+iEv2qQLGPUbkwTz7OoA7yDfS56O6NGk CVZGMYPLfYuvyCMpWJ8tFwoY+r/IBA/t6HRuVXCyeis5wpkIQ9bYS7xOMfNn5GYT1Yoe VbFyTBzQV4Ad6kz4tfBUC5j+id7tm/PpmMOMtZT1aNkN2y8CWRaTtZyRGmL8AX98uXuP XKzvyoUoc6QfK3iWcbMMW45e8xFJ32rYobSYgcndJfcxMqzVi5Bh++X0+CSJzxhl73Yf kOLQ== 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=1zOX9yPoF+2HZpqK6MIH+/PXRsbN5do6/PpWEHqP4fY=; b=H+J1ctG9OimCnPUdklqSXuXBJBnoe+4qqJ3hQ4e+3SDOW7N8ckq2fy6+Dj8gukr7Z9 1chxnK7rqCaCCJMDx+zs1nC4ru3sQ0+bsW2E8oEqSZPMJSyYskeZAIlRRhEHsJDX2UbV sAwG3bBWhbvXSxD9OsdvSK/BpTzGC0acl1weZ0xKCxK5gS4dbBif0/orw0S+tTL8EEdg TXgk937NIe3tcT9yiSvIf2Bn0Ks/OGfKQ8yLNRAWmeHw0agQKOWPRZN3YCL448A7bkpR 0jNF6d0aSld1t2YPra3cCm62Q9iERo6a4aCG4t1EufOvupBBF02GtXfGJQj18EJWPq7/ +zuQ== X-Gm-Message-State: ALoCoQl+nBzpYU78nsHBFX6iEs++cVI/u37SNBoZ7LokLojJ728zXThopRJWTZydTC0JYZPPy7jY X-Received: by 10.58.182.137 with SMTP id ee9mr996130vec.37.1402676670452; Fri, 13 Jun 2014 09:24:30 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.128.110 with SMTP id nn14ls301296igb.1.gmail; Fri, 13 Jun 2014 09:24:28 -0700 (PDT) X-Received: by 10.50.17.100 with SMTP id n4mr105598igd.3.1402676668941; Fri, 13 Jun 2014 09:24:28 -0700 (PDT) In-Reply-To: <30a83c0d-00e6-462a-822e-a1789787ec05@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:11298 Archived-At: ------=_Part_317_24531460.1402676667554 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable W dniu czwartek, 12 czerwca 2014 12:16:04 UTC+2 u=C5=BCytkownik walter1234= =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 bod= y. > > 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)' , an= y=20 > 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 oft= en=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 --=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_317_24531460.1402676667554 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

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 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;   &nb= sp; // 'return_type' is a shortcut for whatever this functions declared ret= urn type is..
      ... do stuff with accumulator.= ...

     return accumulator.
}

ways of doing that without a new keyword, per= haps 'decltype(return)' , any other ideas..
In some ways this wou= ld go beyond what rust currently does. (rust can't yet use an expression fo= r the return type, although making it generic often works because of how th= e return types are inferred by callers)
 =
How about doing it the Go style:
 
auto= foo(  args...  ) -> decltype(....some expression based on arg= s...) accumulator
{   
  do_stuff_with(accumulato= r);
  return accumulator.
}
 

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