220 5308 article Path: news.gmane.org!not-for-mail From: Martinho Fernandes Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Overloaded Declarators Date: Sat, 6 Jul 2013 03:03:37 +0200 Lines: 131 Approved: news@gmane.org Message-ID: References: <82b89c5e-ce4e-49c0-82b2-d6032631e3e3@isocpp.org> <6ed86280-bff9-4dc5-bef3-28be8981770b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1373072619 27915 80.91.229.3 (6 Jul 2013 01:03:39 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 6 Jul 2013 01:03:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDXL3FEUYQARB2OZ3WHAKGQETGXNARA@isocpp.org Sat Jul 06 03:03:41 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qa0-f70.google.com ([209.85.216.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UvGuZ-0003hN-Fl for gclcip-std-proposals@m.gmane.org; Sat, 06 Jul 2013 03:03:39 +0200 Original-Received: by mail-qa0-f70.google.com with SMTP id cr7sf3390635qab.5 for ; Fri, 05 Jul 2013 18:03:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:mime-version:in-reply-to:references:date:message-id :subject:from:to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type:content-transfer-encoding; bh=neDjWtyQ6ekk5RZNZaLolLcrYk8mlOSdlG4spgn+RjA=; b=oUtJcBvL5G7YJJpU8z7XNEFOIjHXPRDzW5FAYgpcnjnwW4syFN55kERmSQOwZsxBkK Uwv4UJAXAupoI9k6RjT1WlU6p0vOzMn5wR0b582rQy1dZ0uTjk97EXLs0ZZbECrPrgU2 mxWjIle9n3xsrg4xv1zJjAcAOul7rRAJFgJR/Dy0R4dglbucWFJpK59hM7nG+vfTqLQr NB786v5VFc+TO6AwGyZ/o/4pJuVVysBvrgS+lxay5aXNueMDz6XPISBnsNrq43bobMMT 2XuzFFOkbwO9y00HpAyzuSZwj9xVb1HaFKnV7RPt5K3TPLligL1B3GKJINY0dQhgMrTI PmdQ== X-Received: by 10.224.205.138 with SMTP id fq10mr14870375qab.1.1373072618461; Fri, 05 Jul 2013 18:03:38 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.49.226 with SMTP id x2ls1106984qen.12.gmail; Fri, 05 Jul 2013 18:03:37 -0700 (PDT) X-Received: by 10.49.127.196 with SMTP id ni4mr7436883qeb.5.1373072617662; Fri, 05 Jul 2013 18:03:37 -0700 (PDT) Original-Received: from mail-qc0-x22a.google.com (mail-qc0-x22a.google.com [2607:f8b0:400d:c01::22a]) by mx.google.com with ESMTPS id o5si2865682qag.187.2013.07.05.18.03.37 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 05 Jul 2013 18:03:37 -0700 (PDT) Received-SPF: pass (google.com: domain of martinho.fernandes@gmail.com designates 2607:f8b0:400d:c01::22a as permitted sender) client-ip=2607:f8b0:400d:c01::22a; Original-Received: by mail-qc0-f170.google.com with SMTP id s1so1510327qcw.1 for ; Fri, 05 Jul 2013 18:03:37 -0700 (PDT) X-Received: by 10.49.74.227 with SMTP id x3mr7168869qev.29.1373072617560; Fri, 05 Jul 2013 18:03:37 -0700 (PDT) Original-Received: by 10.49.94.238 with HTTP; Fri, 5 Jul 2013 18:03:37 -0700 (PDT) In-Reply-To: <6ed86280-bff9-4dc5-bef3-28be8981770b@isocpp.org> X-Original-Sender: martinho.fernandes@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of martinho.fernandes@gmail.com designates 2607:f8b0:400d:c01::22a as permitted sender) smtp.mail=martinho.fernandes@gmail.com; dkim=pass header.i=@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:5308 Archived-At: There is a big problem in that the existing code that wants pointers uses T*, not std::pointerto. And that's a rather *large* body of code. Mit freundlichen Gr=FC=DFen, Martinho On Sat, Jul 6, 2013 at 1:05 AM, wrote: >> What if I want an actual pointer now? > > Suppose you overload unary operator& on a class: > > struct X > { > Y operator&(); > } > > What if I want the actual address of an object of type X now? You use > std::addressof. > > In a similar fashion alias templates could be provided in the standard > library, for example std::pointerto, such that even if the * declarato= r > was overloaded for that class, pointerto would always give you the typ= e > "pointer to T": > -Andrew. > > > On Friday, July 5, 2013 3:57:23 PM UTC+2, R. Martinho Fernandes wrote: >> >> What if I want an actual pointer now? >> Mit freundlichen Gr=FC=DFen, >> >> Martinho >> >> >> On Fri, Jul 5, 2013 at 8:32 AM, wrote: >> > If we view for a moment the various parts of a declarator as operation= s >> > on >> > types: >> > >> > T*: T -> pointer-to-T >> > T&: T -> lvalue-reference-to-T >> > T&&: T -> rvalue-reference-to-T >> > T[]: T -> array-of-T >> > T(): T -> function-returning-T >> > and so forth >> > >> > These operations take one or more types as input and produce a type as >> > output. >> > >> > This is not dissimilar to an alias template: >> > >> > template >> > using MakePointer =3D T*; >> > >> > template >> > using MakeReference =3D T&; >> > >> > In fact we could almost say that functions are to the built-in >> > expression >> > operators, as alias templates are to the built-in declarators. >> > >> > So the proposed feature "Overloaded Declarators" is to enable a >> > user-defined >> > alias template to redefine the built-in meaning of a declarator. >> > >> > Overloaded Declarators are to the built-in declarators, as Overloaded >> > Operators are to the built-in expression operators: >> > >> > struct Foo{} >> > >> > template >> > using operator* =3D shared_ptr; >> > >> > Foo* p; // p has type shared_ptr >> > >> > The above shows a key use case, specializing the declarator `T*` to >> > designate a user-defined smart pointer class instead of pointer-to-T f= or >> > some set of types. >> > >> > Just a random idea. >> > >> > Enjoy, >> > Andrew. >> > >> > -- >> > >> > --- >> > 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-proposal...@isocpp.org. >> > To post to this group, send email to std-pr...@isocpp.org. >> > Visit this group at >> > http://groups.google.com/a/isocpp.org/group/std-proposals/. >> > >> > > > -- > > --- > 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/. > > --=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/. .