220 5297 <82b89c5e-ce4e-49c0-82b2-d6032631e3e3@isocpp.org> article Path: news.gmane.org!not-for-mail From: andrewtomazos@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Overloaded Declarators Date: Thu, 4 Jul 2013 23:32:01 -0700 (PDT) Lines: 104 Approved: news@gmane.org Message-ID: <82b89c5e-ce4e-49c0-82b2-d6032631e3e3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_4435_27230862.1373005921884" X-Trace: ger.gmane.org 1373032296 22942 80.91.229.3 (5 Jul 2013 13:51:36 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 5 Jul 2013 13:51:36 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD5KHQXXWYPRBZE63OHAKGQEW37GXUQ@isocpp.org Fri Jul 05 15:51:37 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vb0-f72.google.com ([209.85.212.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uv6QB-0005oW-0I for gclcip-std-proposals@m.gmane.org; Fri, 05 Jul 2013 15:51:35 +0200 Original-Received: by mail-vb0-f72.google.com with SMTP id p12sf2811830vbe.3 for ; Fri, 05 Jul 2013 06:51:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:date:from:to:message-id: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=TU+fkcahuhGmo7JQeXs3MEIsls+ddi8NLE4KOEqXIzQ=; b=btny7F+SBRff2pLOKVrwRBz1MTa8q31PYf45E7GN5Bf6/80cyjepprMKfgpnBPlvd0 uEOTlMU+bnagGTnbOp9nHBzHLOFwNvkvh1wSI1mguoNnYoOnL0J7Rk8Bdf4dPuGER/nN vsHKAsm/3eNUab127in/F9OS/p548hQxH4bZH7kpwsMTRqW05C9UtV2CHo9OosVoM692 WrEdxM55QywCCUBSSRSJPp/wTRkVS0mx/m7GaSy8j5fxthklnaSkl3ejt1eiO8yS2EBu v/Td5SbdtV0nXRLjSDH1/mH2UfXgyzic3LmgZkB+1R1jMgCrBGCzLPGeHl2Jxidsqv7t Ibeg== X-Received: by 10.236.88.231 with SMTP id a67mr4971890yhf.39.1373032294063; Fri, 05 Jul 2013 06:51:34 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.132.38 with SMTP id or6ls984919qeb.7.gmail; Fri, 05 Jul 2013 06:51:32 -0700 (PDT) X-Received: by 10.224.41.145 with SMTP id o17mr292984qae.3.1373032292438; Fri, 05 Jul 2013 06:51:32 -0700 (PDT) Original-Received: by 10.224.52.77 with SMTP id h13msqag; Thu, 4 Jul 2013 23:32:02 -0700 (PDT) X-Received: by 10.49.17.166 with SMTP id p6mr202976qed.18.1373005922449; Thu, 04 Jul 2013 23:32:02 -0700 (PDT) X-Original-Sender: andrewtomazos@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:5297 Archived-At: ------=_Part_4435_27230862.1373005921884 Content-Type: text/plain; charset=ISO-8859-1 If we view for a moment the various parts of a declarator as operations 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 = T*; template using MakeReference = 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* = 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 for 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-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_4435_27230862.1373005921884 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable If we view for a moment the various parts of a declarator as operations on = types:

    T*: T -> pointer-to-T
  &n= bsp; T&: T -> lvalue-reference-to-T
    T&&= ;: T -> rvalue-reference-to-T
    T[]: T -> array-o= f-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 te= mplate:

   template<class T>
   using M= akePointer =3D T*;

   template<class T>
 &nb= sp; 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 De= clarators" 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 ope= rators:

   struct Foo{}

   template<cl= ass T>
   using operator*<Foo> =3D shared_ptr<T>= ;;

   Foo* p;  // p has type shared_ptr<T>
<= br>The above shows a key use case, specializing the declarator `T*` to desi= gnate a user-defined smart pointer class instead of pointer-to-T for some s= et of types.

Just a random idea.

Enjoy,
Andrew.

--
 
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