220 20416 article Path: news.gmane.org!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Usability improvement: Unambiguously resolve overloaded functions when passed as function parameters Date: Fri, 11 Sep 2015 11:10:22 -0400 Lines: 49 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: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1441984277 15352 80.91.229.3 (11 Sep 2015 15:11:17 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 11 Sep 2015 15:11:17 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBB6G5ZOXQKGQEGMSQJWQ@isocpp.org Fri Sep 11 17:11:08 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lb0-f199.google.com ([209.85.217.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZaPya-0007rC-8r for gclcip-std-proposals@m.gmane.org; Fri, 11 Sep 2015 17:10:56 +0200 Original-Received: by lbcao8 with SMTP id ao8sf25492464lbc.1 for ; Fri, 11 Sep 2015 08:10:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:to:from:subject:date:lines:message-id:references :mime-version:content-type:user-agent:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=mRLyE14FtpQQ8uU/yaKt4jGIctgqVFdeWmznL4Wcj34=; b=KNsfulRxN9iIJ4s1zwEDRYlfkQXFNswbKFnKdzfbxEW48izloYLQ9xwhDF5gU3/Nhj 9woQ525+pJdY+dOS1KTmYBIQRVf3xtrzHLu6Tkt6Z37c20s6xEK63fbcTdcBpt5YWTNj vQBVpiwWCpykh/wGHC/EVoF2q17PN3GNYWBn3u9/FOeadOI4qqsHAwpk+XHnzSx34J0O Wjx8SKxv6GKenx4BLSH+u7h945kmGIfo+sA2hjt2+CcM7AiTWflaTnprlRpMpWhRGBiB qPqLiWRT1pnatU2g46WNwrk/ic4EdIKaYcAE9jvNWiqxWKyueqD7PJQyuBfRMd5u8mOF X-Gm-Message-State: ALoCoQmDGgPec/vDnB/0CjL/V9VB7Uc/aJJKYE3vNBJ/J+9A0dKwzHdYFiys74GUcowcl2v5ygVB X-Received: by 10.112.139.137 with SMTP id qy9mr11271718lbb.17.1441984250895; Fri, 11 Sep 2015 08:10:50 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.28.66 with SMTP id z2ls315392lag.76.gmail; Fri, 11 Sep 2015 08:10:48 -0700 (PDT) X-Received: by 10.152.7.106 with SMTP id i10mr42693160laa.114.1441984248041; Fri, 11 Sep 2015 08:10:48 -0700 (PDT) Original-Received: from plane.gmane.org (plane.gmane.org. [80.91.229.3]) by mx.google.com with ESMTPS id ry9si507376lbb.99.2015.09.11.08.10.48 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 11 Sep 2015 08:10:48 -0700 (PDT) Received-SPF: pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZaPyI-0007cf-Dg for std-proposals@isocpp.org; Fri, 11 Sep 2015 17:10:38 +0200 Original-Received: from tripoint.kitware.com ([66.194.253.20]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 11 Sep 2015 17:10:38 +0200 Original-Received: from mwoehlke.floss by tripoint.kitware.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 11 Sep 2015 17:10:38 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 40 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: tripoint.kitware.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) smtp.mailfrom=gclcip-std-proposals@m.gmane.org; dmarc=fail (p=NONE dis=NONE) header.from=gmail.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:20416 Archived-At: On 2015-09-10 23:29, german.diago@hubblehome.com wrote: >> Less of an improvement than your macro, but it might be cool to see >> [snipped] >> >> 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 > compilerinliners, I am pretty sure it is very easy to eliminate the > overhead of the lambdas. Even in a case like this? void foo(void (*)(int)); void foo(std::function); foo(overloaded(bar)); To be equally as efficient, the above would have to resolve to a call of 'void foo(void (*)(int))' with '&bar' (proper overload selected) as the parameter. This happens with my helper function. I'm less sure it would happen, or even if it legally *can* happen, with your lambda wrapper. >> 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. Well, yes, but I suppose my point is that your solution is not usable for this case. Signals/slots *must* be fully resolved at call time (the signal, at least). Also, I'm not sure if Qt's parameter matching would work with templated lambdas. -- Matthew -- --- 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/. .