220 20405 article Path: news.gmane.org!not-for-mail From: german.diago@hubblehome.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Usability improvement: Unambiguously resolve overloaded functions when passed as function parameters Date: Thu, 10 Sep 2015 20:29:07 -0700 (PDT) Lines: 136 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_472_322957566.1441942147695" X-Trace: ger.gmane.org 1441942156 26271 80.91.229.3 (11 Sep 2015 03:29:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 11 Sep 2015 03:29:16 +0000 (UTC) Cc: mwoehlke.floss@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDKJVOEEVYNRBBEVZGXQKGQEMCD5YOY@isocpp.org Fri Sep 11 05:29:15 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f72.google.com ([209.85.218.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZaF1S-0002Ux-7X for gclcip-std-proposals@m.gmane.org; Fri, 11 Sep 2015 05:29:10 +0200 Original-Received: by oiww128 with SMTP id w128sf96046467oiw.0 for ; Thu, 10 Sep 2015 20:29:09 -0700 (PDT) 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:cc:message-id:in-reply-to :references:subject:mime-version:content-type:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=iiLDK/ek3GupeE3hSQcxIvhX76EvCPeWD/kpiJyIBsM=; b=dtbkLWLkP9d2+2i59Mi+uKpJ+J83AlDeZNIrl7KFMusjRsOsY+SIczlqTBdfWKv0ZY dkoLXFeAUyUAPPOPJwRA4aOUnyPYnMUHqHL16OAGgSI1EmblOZ7wD5S7/HViK+6VHhOr TTs16X/3N2kOniA5l3ErprsED7oprllbef2R3+gomkZC7F0V1ibb6hUf55bdX45lpX5Z 2m75KRc7qZ8ozIotxD68KbJev6k+ataCsutS3fJVeeEJdZYmuudv2TlQuINue4RVA7pG lXqVAYQhXreQu0bgNBoyhySAwgDjJhiGNZaePekqpHcs8f5YUHN51hxn7dyr0uW/8gJE jA1g== X-Gm-Message-State: ALoCoQkYdEf2rL+vatLRBOsw/zk08oz+P6cqy+3/WKlTZTc3JwmlbMS13LrtQmjMwBYzucHaLz9q X-Received: by 10.182.128.101 with SMTP id nn5mr40091961obb.31.1441942149319; Thu, 10 Sep 2015 20:29:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.122.106 with SMTP id lr10ls427705igb.9.gmail; Thu, 10 Sep 2015 20:29:08 -0700 (PDT) X-Received: by 10.50.77.39 with SMTP id p7mr85889igw.7.1441942148562; Thu, 10 Sep 2015 20:29:08 -0700 (PDT) In-Reply-To: X-Original-Sender: german.diago@hubblehome.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:20405 Archived-At: ------=_Part_472_322957566.1441942147695 Content-Type: multipart/alternative; boundary="----=_Part_473_1713470962.1441942147696" ------=_Part_473_1713470962.1441942147696 Content-Type: text/plain; charset=UTF-8 Less of an improvement than your macro, but it might be cool to see > these standardized (especially if a better solution is not forthcoming): > > template > auto overload(R (T::*m)(Args...)) -> decltype(m) > { return m; } > > template > auto overload(R (T::*m)(void)) -> decltype(m) > { return m; } > Well, it is better than current status, but why not go directly for a full solution? > On the plus side, not a macro, and resolves to the desired overload > directly rather than adding an indirection through a templated lambda > (even if the compiler is able to optimize that away, though I don't know > that I would count on it being able to do so). > Taking into account that a lambda is declared inline, with current compiler inliners, I am pretty sure it is very easy to eliminate the overhead of the lambdas. > > The above is irresolvably ambiguous without additional information, > because either noise(int) + listen(int) or noise(float) + listen(float) > would be acceptable. (This is where the above 'overload<...>' is most > useful.) > Well, actually my solution does not choose one function at the time of connection, at that time you would pass an overloaded function object. > Here's a silly notion: what if we allowed <>'s after any overloaded > function to select a particular overload? IOW: > > connect(foo, &Foo::noise, bar, &Bar::listen); > I think this makes the pointer to member to look like a template, when in fact it is not. So I would choose something else. -- --- 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_473_1713470962.1441942147696 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Less of an improvement than your macro, but it might be co= ol to see
these standardized (especi= ally if a better solution is not forthcoming):

=C2=A0 =C2=A0 template<class... Args, class T, class R>
=C2=A0 =C2=A0 auto overload(R (T::*m)(Args...)) -> decltype(m)
=C2=A0 =C2=A0 { return m; }

=C2=A0 =C2=A0 template<class T, class R>
=C2=A0 =C2=A0 auto overload(R (T::*m)(void)) -> decltype(m)
=C2=A0 =C2=A0 { return m; }

Well, it is better than current status, but why n= ot go directly for a full solution?
=C2=A0
On the plus side, not a macro, and resolves to the= desired overload
directly rather than adding an indirection through a templated lambda
(even if the compiler is able to optimize that away, though I don't= know
that I would count on it being able to do so).

Taking into account that a lambda is declared inl= ine, with current compiler inliners,
I am pretty sure it is very easy to= eliminate the overhead of the lambdas.
=C2=A0

The above is irresolvably ambiguous withou= t additional information,
because either noise(int) + listen(int) or noise(float) + listen(float)
would be acceptable. (This is where the above 'overload<...>&= #39; is most
useful.)

Well, actually my solution does not choose one fu= nction at the time of connection,
at that time you would pass an overloa= ded function object.
=C2=A0
Here's a silly notion: what if we allowed <>'s afte= r any overloaded
function to select a particular overload? IOW:

=C2=A0 connect(foo, &Foo::noise<int>, bar, &Bar::listen&l= t;int>);

I think this makes the pointer to member to look = like a template, when in fact it is not.
So I would choose something els= e.
=C2=A0
=C2=A0

--

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