220 6762 article Path: news.gmane.org!not-for-mail From: tomaszkam@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Revision of N3702: Introducing an optional parameter for mem_fn. Date: Sun, 29 Sep 2013 05:17:56 -0700 (PDT) Lines: 92 Approved: news@gmane.org Message-ID: References: <0ffade3d-ac13-434c-b20a-85d611783fc1@isocpp.org> <2284c2d2-ec8e-43fb-90e7-c43ac9dc92c2@isocpp.org> <505813ae-956c-4693-b793-2ba47107c09c@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_89_22566674.1380457076201" X-Trace: ger.gmane.org 1380457076 29876 80.91.229.3 (29 Sep 2013 12:17:56 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 29 Sep 2013 12:17:56 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDNPVXXG6IGBB5NUUCJAKGQE3SRQKUY@isocpp.org Sun Sep 29 14:18:00 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f198.google.com ([209.85.214.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VQFwl-0001aa-4o for gclcip-std-proposals@m.gmane.org; Sun, 29 Sep 2013 14:17:59 +0200 Original-Received: by mail-ob0-f198.google.com with SMTP id uy5sf17357906obc.9 for ; Sun, 29 Sep 2013 05:17:58 -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=RMDNdONjHcV9sKCNsmFLMxkJa16T1XpBdt9Z+HspHKQ=; b=RySWqytk+VZshwzVrgjGVTg26Ryvb3Oe9uKwq/jss+9TY2lzj2DFizkRwQHCR8wAsm d2vvuHr+DxNr/kW8EKOsN70sv6yVSHVCgsJNemTgODCy3VeyCSZvZVx4SnOl+NZPGrz6 sGnQRZCqV5Q3Ly4jcU4yH1k0xDVavkamLspVAbcnokM3+Uca5LUMV+y2wsJm+yF8azPC YeKuktOCdg9pusLVTpKPZNLQ/C/ysd685uH/zNtDpFkLIwyhRnupAtVuuT58z2RkuhhY v/XsOUUOEWJU5u7VJS3jbeQAfiO2PQU56WklYyT7uxUaltWXSLUjsQlcx6clPSP3ygEq 58hg== X-Received: by 10.43.65.81 with SMTP id xl17mr10379777icb.29.1380457078120; Sun, 29 Sep 2013 05:17:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.33.45 with SMTP id o13ls1352132igi.17.canary; Sun, 29 Sep 2013 05:17:57 -0700 (PDT) X-Received: by 10.50.11.16 with SMTP id m16mr297930igb.0.1380457077685; Sun, 29 Sep 2013 05:17:57 -0700 (PDT) In-Reply-To: X-Original-Sender: tomaszkam@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:6762 Archived-At: ------=_Part_89_22566674.1380457076201 Content-Type: text/plain; charset=ISO-8859-2 Content-Transfer-Encoding: quoted-printable W dniu niedziela, 29 wrze=B6nia 2013 06:26:18 UTC+2 u=BFytkownik Jeffrey=20 Yasskin napisa=B3: > > Thanks for the proposals. The Library Evolution group in Chicago=20 > reviewed mem_fn and concluded that it's generally not worth extending=20 > the callable wrappers, and that users should just use lambdas in=20 > nearly all cases. C++14's generic lambdas with variadic captures make=20 > this an even better tradeoff (note, I didn't compile this):=20 > > double r =3D integrate=20 > ([&a](const auto&... args) { return a.fa(args...);},=20 > x1, x2, y1, y2, z1, z2, a1, a2, b1, b2);=20 > > To work with any parameter/return (references) type combination, this=20 should be written as: double r =3D integrate( [&a](auto&&... args) -> decltype(auto) { return a.fa(std::forward(args)...); }); Which is pretty less readable and less intent clear than: double r =3D integrate(std::mem_fn(&A::a, std::ref(a))); In my opinion the deifference between this 2 cases may be compared with the= =20 diference between using hand-writtern loop versus algorithm. --=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_89_22566674.1380457076201 Content-Type: text/html; charset=ISO-8859-2 Content-Transfer-Encoding: quoted-printable


W dniu niedziela, 29 wrze=B6nia 2013 06:26:18 UTC+= 2 u=BFytkownik Jeffrey Yasskin napisa=B3:
Thanks for the proposals. The Library Evolution group in Chicago
reviewed mem_fn and concluded that it's generally not worth extending
the callable wrappers, and that users should just use lambdas in
nearly all cases. C++14's generic lambdas with variadic captures make
this an even better tradeoff (note, I didn't compile this):

 double r =3D integrate
              ([&a](const auto&a= mp;... args) { return a.fa(args...);},
                 x1, x2, y= 1, y2, z1, z2, a1, a2, b1, b2);

To work with any parameter/return (references) type c= ombination, this should be written as:
 double r =3D integrate(
    = ;          [&a](auto&&= amp;... args) -> decltype(auto)
          &n= bsp;   { return a.fa(std::forward<decltype(auto)>(args)...); });=

Which is pretty less readable and less intent clear than: double r =3D int= egrate(std::mem_fn(&A::a, std::ref(a)));

In my opinion the deifference between this 2 cases may be compared= with the diference between using
hand-writtern loop versus algorithm.

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