220 4650 <3100c7f2-43d6-4f28-a7ec-54a2f6e94d21@isocpp.org> article Path: news.gmane.org!not-for-mail From: Jonathan Wakely Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Extension to std::function to allow binding a object to its member function Date: Tue, 28 May 2013 05:09:06 -0700 (PDT) Lines: 96 Approved: news@gmane.org Message-ID: <3100c7f2-43d6-4f28-a7ec-54a2f6e94d21@isocpp.org> References: <6472bf39-fa71-4947-ae99-df011d5435e2@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_3915_5041585.1369742946289" X-Trace: ger.gmane.org 1369742952 25110 80.91.229.3 (28 May 2013 12:09:12 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 28 May 2013 12:09:12 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCMONUNYS4IRBY54SKGQKGQE2RKWOKI@isocpp.org Tue May 28 14:09:10 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yh0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UhIiC-0003FZ-GO for gclcip-std-proposals@m.gmane.org; Tue, 28 May 2013 14:09:08 +0200 Original-Received: by mail-yh0-f69.google.com with SMTP id i72sf6080539yha.0 for ; Tue, 28 May 2013 05:09:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-beenthere:date:from:to:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-google-group-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=dyvOpHdp1LHJ+PAn7FaoviGlkD42d0gz2WSfBz53HLM=; b=kZmbCLFdOkDmiYxDFp/+4aK1U+gVidtlK3AkytUSK86cN6/bS1Gfd9Fot9S796nIA5 yFRWxFPGseXRnJBNex+7YCV8pfYDBeUyypLZSFhYxaz+CvCll2F0mKYSA2G3FmgYrPj/ TWR/SokJ5Lh/iWU5PwVTDTcp+kCn1vQvutlIi8ffBx5jNg0ZSzcHRbNHcWUVLIpruwRb qaHKbdZe3ivRMHGWkJX3EPUkMvPXShu7ME09h7pVHYOsr1JWtE6mpCQKsXoJatZq1rOv 7W4ga3dlSN09PCMkOms0MjsjWH3BBOG5YEeKS6UAtG1AiW0oIsXj2VVlB7vBd4yRaNhq xRXg== X-Received: by 10.224.36.66 with SMTP id s2mr17405237qad.6.1369742947637; Tue, 28 May 2013 05:09:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.98.99 with SMTP id eh3ls688924qeb.15.gmail; Tue, 28 May 2013 05:09:06 -0700 (PDT) X-Received: by 10.49.95.3 with SMTP id dg3mr201943qeb.41.1369742946611; Tue, 28 May 2013 05:09:06 -0700 (PDT) In-Reply-To: X-Original-Sender: cxx@kayari.org 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:4650 Archived-At: ------=_Part_3915_5041585.1369742946289 Content-Type: text/plain; charset=ISO-8859-1 On Monday, May 27, 2013 2:32:17 PM UTC+1, Ville Voutilainen wrote: > > >> First of all, the standard function + bind will not allow to do this. >> > > I don't quite grasp what you think std::function and std::bind don't allow. > This proposal would allow you to refer to an overloaded member function without an explicit cast or other means to specify the desired overload, e.g. struct A { void f(); int f(int); } a; std::function f1(&a, &A::f); // chooses first overload That's quite convenient. However it isn't as flexible: std::function allows implicit conversions on the return type and arguments, but using this proposal you'd have to be precise, e.g. std::function f2(&a, &A::f); // error std::function f3(&a, &A::f); // error Both of those will work using std::bind (and a cast to select the overload), but with this proposal you'd have to do: std::function f2 = std::function(&a, &A::f); std::function f3 = std::function(&a, &A::f); -- --- 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/?hl=en. ------=_Part_3915_5041585.1369742946289 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

On Monday, May 27, 2013 2:32:17 PM UTC+1, Ville Voutilainen wrote:<= blockquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;bord= er-left: 1px #ccc solid;padding-left: 1ex;">


First of all, the s= tandard function + bind will not allow to do this.


I don't quite grasp what you think std::function and std::= bind don't allow.

This pro= posal would allow you to refer to an overloaded member function without an = explicit cast or other means to specify the desired overload, e.g.

s= truct A
{
  void f();
  int f(int);
} a;

std::= function<void()> f1(&a, &A::f);  // chooses first overlo= ad

That's quite convenient.  However it isn't as flexible: std:= :function allows implicit conversions on the return type and arguments, but= using this proposal you'd have to be precise, e.g.

std::function<= ;void(int)> f2(&a, &A::f);  // error
std::function<sh= ort(short)> f3(&a, &A::f);  // error

Both of those w= ill work using std::bind (and a cast to select the overload), but with this= proposal you'd have to do:

std::function<void(int)> f2 =3D st= d::function<int(int)>(&a, &A::f);
std::function<short(s= hort)> f3 =3D std::function<int(int)>(&a, &A::f);

&= nbsp;

--
 
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