220 11265 <30a83c0d-00e6-462a-822e-a1789787ec05@isocpp.org> article Path: news.gmane.org!not-for-mail From: walter1234 Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: return type sugar (orthogonal to auto foo() {} ) Date: Thu, 12 Jun 2014 03:16:04 -0700 (PDT) Lines: 74 Approved: news@gmane.org Message-ID: <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_87_22099948.1402568164130" X-Trace: ger.gmane.org 1402568173 32698 80.91.229.3 (12 Jun 2014 10:16:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 12 Jun 2014 10:16:13 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDO7FOW36ILRBZP34WOAKGQEJI7FRPQ@isocpp.org Thu Jun 12 12:16:07 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qc0-f200.google.com ([209.85.216.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Wv23C-0008LT-Ug for gclcip-std-proposals@m.gmane.org; Thu, 12 Jun 2014 12:16:07 +0200 Original-Received: by mail-qc0-f200.google.com with SMTP id o8sf3950654qcw.7 for ; Thu, 12 Jun 2014 03:16:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id: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=mcaXtgSxhZRQmaWMXoOBNmNc8EqI40ftE9/8+NqXwwI=; b=ufg6pzwSQgUy0weWeHzvmOdeyEXckGTZNK1UbMdkl07R2TYRoHShi4V8Wsov4dpNeX 4RUjhWWhuYlwnSkpYAMF2oTJLMeMxxzCbSy4woMzCjuTrbgknUB4/kEm2/sKiRbJUjp/ /ER6S3RAhxG8pUHqHkREpWDiyunhxnddp7kqHHEPmF9lrnBYelOW1J48c8o5OEzhDzou qym5yeNjsp0QnjMMz9yh1CiHbNkf00aOJHTM/HyhRwVvBonqCDD3OmdGLDKhc9OGn3n1 RIR8NBDumiySvRoq3nKp7SAxjbYMlRMUVpnVa8ohPRro5gGpeEie2ngdrEb/OXgP54XC Bsig== 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: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=mcaXtgSxhZRQmaWMXoOBNmNc8EqI40ftE9/8+NqXwwI=; b=JlCbRPZESSIKW7+vRA54e0u1HVjTAtbMGN4j03bb+wyyXQO9/vk0/+HTAsRZyA07qU 03+vptsysE3Zls2yDQVGn6Q3EDYGu35WVZalU8Iit8bj5olVx/Shkdp6P2G2dbsRgaVe o8BJ34XLfR7Q/e59ZrCtLKO3FwwICc0K7HzI83jLEZQXVQ8XleP3x4KjCztgreKhN/y/ i8H0p303V4PynDqF8UtQ5Qqfd9pScFrzl7J7ILZT9nH3Yn7pMbu4pqeNNrt/JS00uI/f NqoP9AXo7tQFHCjaOSdBozPXr4TMl1UsTXnxduXCIN8PDCTgwSJtwYxdHvb9EKu+fH37 Usyw== X-Gm-Message-State: ALoCoQm02CWZ8MYBtsok2t784f4Tz5Lb40+JhUqcc4EcHxMjwXuc6AcM0YzySSrRF8irzX9pykLq X-Received: by 10.58.134.36 with SMTP id ph4mr9016907veb.27.1402568165981; Thu, 12 Jun 2014 03:16:05 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.131.229 with SMTP id op5ls1648258igb.34.gmail; Thu, 12 Jun 2014 03:16:05 -0700 (PDT) X-Received: by 10.50.7.97 with SMTP id i1mr86903iga.8.1402568165289; Thu, 12 Jun 2014 03:16:05 -0700 (PDT) X-Original-Sender: walter2bz@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:11265 Archived-At: ------=_Part_87_22099948.1402568164130 Content-Type: text/plain; charset=UTF-8 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) -- --- 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/. ------=_Part_87_22099948.1402568164130 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Coming back to C++ from Rust, one thing begin to miss is t= he 2way type inference: its a nice choice on their part, you write the type= s in the signature, then the types in the body are inferred.

=
But perhaps a significant amount of this use could be covered by havin= g sugar to access the declared return type of a function within its own bod= y.

imagine

auto foo( &nbs= p;args...  )->decltype(....some expression based on args...) {

      return_type  accumulator; &n= bsp;   // 'return_type' is a shortcut for whatever this functions decl= ared return type is..
      ... do stuff with accu= mulator...

     return accumulator.=
}

ways of doing that without a new keyw= ord, perhaps 'decltype(return)' , any other ideas..
In some ways = this would go beyond what rust currently does. (rust can't yet use an expre= ssion for the return type, although making it generic often works because o= f how the return types are inferred by callers)

--

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