220 12732 <2285060d-e475-48f8-a9cc-389487ee681f@isocpp.org> article Path: news.gmane.org!not-for-mail From: Matthew Fioravante Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Usability extensions to offsetof Date: Mon, 8 Sep 2014 11:05:31 -0700 (PDT) Lines: 90 Approved: news@gmane.org Message-ID: <2285060d-e475-48f8-a9cc-389487ee681f@isocpp.org> References: <1790122.GP859xiMW3@tjmaciei-mobl4> <3079502.NAEi170Di4@tjmaciei-mobl4> <07066304-6357-4a10-824b-7c0451608996@isocpp.org> <13fd60e5-2882-48bc-a9df-3c8d38b416eb@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_556_866220740.1410199531900" X-Trace: ger.gmane.org 1410199541 13835 80.91.229.3 (8 Sep 2014 18:05:41 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 8 Sep 2014 18:05:41 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELF54RTIGRB3G7W6QAKGQEDQPMR3A@isocpp.org Mon Sep 08 20:05:35 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yh0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XR3Jm-000402-B7 for gclcip-std-proposals@m.gmane.org; Mon, 08 Sep 2014 20:05:34 +0200 Original-Received: by mail-yh0-f69.google.com with SMTP id a41sf16159912yho.4 for ; Mon, 08 Sep 2014 11:05:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=j8q+GysHtIptxl1zdTRRSIJkD251WCVhcPBoJLNYuGo=; b=pG8lhigLVrUUIaC9Xd6Dm38RLq9H1HFuAMqD/pEQ66/vuXYHXcs0vwkqKtOgcd1hQ/ UqTap7r5q3b3NadZMDxJIgofJVoNwBBpOy8FqEirlZJnQ5xAN0M6ngRw84Lb/YwodE1j uvD8DCIt+lL7bGBl4KdI8tTjt7qZpnI03iPXxgr5blu3RsL/atmOSUiZ/+d/YFDHVbyL diKUhZmCeqvuiBBuQERZCPLMJ7/osCPQcdMQNyK68bTmqds62sDyx9eavmUkhq0AdaJI 2FPPcWBTp/pxjxz21LhFinKgRz6Xm8o6Db98CJyVXHyKxp+u4EN+ja0lwcyxOE7WDOhC EVbw== 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:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=j8q+GysHtIptxl1zdTRRSIJkD251WCVhcPBoJLNYuGo=; b=RhbNZ4zjW0mgaWnlnLQc9K0QTCkxeJtcwO8C4VCTJuJ3omHJpG3+A1TNx8G5BvuppL i8aVMT36MRTaB/OZ6AO/Qnz1Yk8rU6v+KcfiVrt25v6H/hqoAj0hdeitIkN3z8yL9dn8 5X3hP/9OmdhnQz4J+B/8WpAuEhd3uwAepy7MoFITZQdVWinI7hKKI7dmHcaxaM78jwhH c3I5x4MkPkm+9/h4QDTQy6oWiah1Lc41zkkxN5yi0JHk6MB8W5M65wVe2Yndac+IHH7Y UiOq+gNyoaslsfLdwtNm/8TsXPJXuJ+REHYbu08Zo2c59F1fQv8U6GL59ueXOd2Iel1D Xc+Q== X-Gm-Message-State: ALoCoQmyw3+hDL/IHDMy6gYU3ZOXXHUixbLJQxcdTD2cild3Z9wuKVOZ4HBDFc99OjdmI5wMmhSX X-Received: by 10.236.230.106 with SMTP id i100mr18190838yhq.27.1410199533295; Mon, 08 Sep 2014 11:05:33 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.91.164 with SMTP id z33ls320886qgd.99.gmail; Mon, 08 Sep 2014 11:05:32 -0700 (PDT) X-Received: by 10.140.33.161 with SMTP id j30mr692361qgj.4.1410199532602; Mon, 08 Sep 2014 11:05:32 -0700 (PDT) In-Reply-To: <13fd60e5-2882-48bc-a9df-3c8d38b416eb@isocpp.org> X-Original-Sender: fmatthew5876@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:12732 Archived-At: ------=_Part_556_866220740.1410199531900 Content-Type: text/plain; charset=UTF-8 On Sunday, September 7, 2014 6:57:26 PM UTC-4, Bengt Gustafsson wrote: > > Inner classes: If the only instance of the inner class is by value in its > outer class then we could accomplish accessing the outer class's members > without any coding: > > class Outer { > int x; > > class Inner { > void f() { > int y = x; // This is assigning from Outer's x. > } > } m_inner; > }; > > I think this should require some extra syntax to enforce that Inner is only allowed to be instantiated in one place and only as a value data member of Outer. Something like: class Outer { int x; static class Inner { void f() { int y = x; } } _inner1; //<-OK Inner _inner2; //<- ERROR: cannot create multiple instances of a static nested class static class AnotherInner {}; //<-ERROR: cannot define a static nested class without also instantiating a value data member }; -- --- 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_556_866220740.1410199531900 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Sunday, September 7, 2014 6:57:26 PM UTC-4, Ben= gt Gustafsson wrote:
Inner classes: If the only instance of the inner class is by value= in its outer class then we could accomplish accessing the outer class's me= mbers without any coding:

class Outer {
 =   int x;

    class Inner {
        void f() {
      &n= bsp;     int y =3D x; // This is assigning from Outer's x.
<= div>        }
    } m_inner;
<= div>
};


I think this should = require some extra syntax to enforce that Inner is only allowed to be insta= ntiated in one place and only as a value data member of Outer.

Somet= hing like:

class Outer {
  int x;
  static class Inn= er {
    void f() { int y =3D x; }
  } _inner1; //<= -OK
  Inner _inner2; //<- ERROR: cannot create multiple instance= s of a static nested class
  static class AnotherInner {}; //<-E= RROR: cannot define a static nested class without also instantiating a valu= e data member
};


--

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