220 5299 <6259ff1e-c669-4ddd-b3c8-941a3bf122cb@isocpp.org> article Path: news.gmane.org!not-for-mail From: Jonathan Wakely Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Extend defition of INVOKE for member pointers to support types convertible to target class. Date: Fri, 5 Jul 2013 09:47:13 -0700 (PDT) Lines: 73 Approved: news@gmane.org Message-ID: <6259ff1e-c669-4ddd-b3c8-941a3bf122cb@isocpp.org> References: <63c352e7-5289-4bfa-9f1a-65cd55478391@isocpp.org> <87a9m1j53t.fsf@euclid.axiomatics.org> <3b278ff7-0487-48db-a1e8-6cf8ff7db5b1@isocpp.org> <87hag9bzmo.fsf@euclid.axiomatics.org> <7955cba4-906f-40b4-ae6d-7ef9dfe59181@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_7004_26154865.1373042833850" X-Trace: ger.gmane.org 1373042834 8582 80.91.229.3 (5 Jul 2013 16:47:14 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 5 Jul 2013 16:47:14 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCMONUNYS4IRBEXR3OHAKGQEEJUTZUQ@isocpp.org Fri Jul 05 18:47:16 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f199.google.com ([209.85.220.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uv9AB-0006f4-Pb for gclcip-std-proposals@m.gmane.org; Fri, 05 Jul 2013 18:47:16 +0200 Original-Received: by mail-vc0-f199.google.com with SMTP id gf11sf2909561vcb.10 for ; Fri, 05 Jul 2013 09:47:15 -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=G5ln1aIqrHcACRsrW+IKWtRL4C47V+X53oTLkZxD/+A=; b=QhCN5BxXG/vH7b5E/OI7IZgZdIYiSvODpuMhnHXljHQFGVeWZov07rXiUKQy7Q0q8k Au3gtJE5PD5kJi5nG3M41ruBeMzWcrYEowqBljVduZbMKMw0Y3I5ontWErwy5gCezyl7 1Pyu85WOum9Cp1KaOIyBrtc4Fh4OiP0uKgwoOJLsWdEPKJKJsKB1wKyPl22MALRFKzdL TvvND1GwzVw7J7O5U8tEkSx+tW6+fwAMYuEXQ3nJP9JWZYVy9BFNxRRnWEyPKT0qtvxx QwLCWeTRZCggRVNuqHRA5Uu2o8/RuIcWuICqcXyUtlvmJwMpstM2SRJMxGSMNxK5cWSk jtjQ== X-Received: by 10.236.42.116 with SMTP id i80mr5524635yhb.26.1373042834865; Fri, 05 Jul 2013 09:47:14 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.50.167 with SMTP id d7ls1076148qeo.25.gmail; Fri, 05 Jul 2013 09:47:14 -0700 (PDT) X-Received: by 10.49.4.136 with SMTP id k8mr255453qek.19.1373042834239; Fri, 05 Jul 2013 09:47:14 -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:5299 Archived-At: ------=_Part_7004_26154865.1373042833850 Content-Type: text/plain; charset=ISO-8859-1 On Friday, July 5, 2013 1:40:07 PM UTC+1, Ville Voutilainen wrote: > > It's not just a matter of taste. The apparently current preference of > operator* (even if as a result of not considering > conversions functions at all) is the status quo in a released standard. > Breaking those semantics should not > be done lightly, even if some personal preference suggests otherwise. > > Making *any* changes to the INVOKE semantics should not be done lightly, it's seriously tricky stuff! I'd like to see some more convincing motivation for this change. std::reference_wrapper is a good motivating case, but I'm less sure about boost::reference_wrapper ... do you really need another reference_wrapper if you have a C++11 implementation? (I'm aware that the boost one allows incomplete types.) Such wrapper types can always be made to work with INVOKE by providing operator* so the last bullet of INVOKE handles them, although that's a bit smelly, I admit. -- --- 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_7004_26154865.1373042833850 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Friday, July 5, 2013 1:40:07 PM UTC+1, Ville Voutilainen wrote:
It's not just a matter of taste. The apparently current pref= erence of operator* (even if as a result of not considering
conversions = functions at all) is the status quo in a released standard. Breaking those = semantics should not
be done lightly, even if some personal preference suggests otherwise.


Making *any* changes to the= INVOKE semantics should not be done lightly, it's seriously tricky stuff!<= br>
I'd like to see some more convincing motivation for this change.&nbs= p; std::reference_wrapper is a good motivating case, but I'm less sure abou= t boost::reference_wrapper ... do you really need another reference_wrapper= if you have a C++11 implementation?  (I'm aware that the boost one al= lows incomplete types.)   Such wrapper types can always be made t= o work with INVOKE by providing operator* so the last bullet of INVOKE hand= les them, although that's a bit smelly, I admit.

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