220 38042 <75fb8736-b92a-480f-9a36-310b3e03b131@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Phil Bouchard Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Fornux C++ Superset - Forward Declarations of Nested Structures Date: Wed, 2 May 2018 04:26:52 -0700 (PDT) Lines: 140 Approved: news@gmane.org Message-ID: <75fb8736-b92a-480f-9a36-310b3e03b131@isocpp.org> References: <34fa23ed-1fab-44d5-92ab-217067b68225@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_27889_582949377.1525260412394" X-Trace: blaine.gmane.org 1525260287 12428 195.159.176.226 (2 May 2018 11:24:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 2 May 2018 11:24:47 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCAYTFXFZMBBB7OAU3LQKGQEVHPVI7I@isocpp.org Wed May 02 13:24:43 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f198.google.com ([209.85.217.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fDpsJ-00038G-08 for gclcip-std-proposals@m.gmane.org; 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Wed, 02 May 2018 04:26:53 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a1f:5cd2:: with SMTP id q201-v6ls8004118vkb.21.gmail; Wed, 02 May 2018 04:26:53 -0700 (PDT) X-Received: by 2002:a1f:2f8b:: with SMTP id v133-v6mr2829678vkv.10.1525260412875; Wed, 02 May 2018 04:26:52 -0700 (PDT) In-Reply-To: <34fa23ed-1fab-44d5-92ab-217067b68225@isocpp.org> X-Original-Sender: philippeb8@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:38042 Archived-At: ------=_Part_27889_582949377.1525260412394 Content-Type: multipart/alternative; boundary="----=_Part_27890_1897469063.1525260412394" ------=_Part_27890_1897469063.1525260412394 Content-Type: text/plain; charset="UTF-8" On Wednesday, May 2, 2018 at 6:58:06 AM UTC-4, Phil Bouchard wrote: > > > > On Wednesday, May 2, 2018 at 12:27:16 AM UTC-4, Richard Smith wrote: >> >> See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0289r0.pdf >> >> The paper received some support from evolution. Some felt that the right >> answer was to wait for Modules. As noted in the above paper there are some >> open questions as to how this would actually work if we went forward with >> it. >> > > 1) I personally would consider the possibility of declaring pointers of > nested classes based on the forward declaration of the aforementioned > nested class at all times. Ex.: > > class X; > struct X::A; > > X::A * p = nullptr; // fine > > 1.1) > class X > { > }; // error caught here: missing class A > > 1.2) > class X > { > struct A; > }; // error caught here: private member and already used as public > Unless we bring the notion of "partial declarations" and forward declarations of nested structures are made like this: class X { struct A; .... // ellipsis operator here }; X::A * p = nullptr; // error class X { struct A; void foo() { X::A * p = nullptr; // fine } }; This way that would solve the access scope problem cleanly. Regards, -Phil -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/75fb8736-b92a-480f-9a36-310b3e03b131%40isocpp.org. ------=_Part_27890_1897469063.1525260412394 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Wednesday, May 2, 2018 at 6:58:06 AM UTC-4, Phi= l Bouchard wrote:


On Wednesday, May 2, 2018 at 12:27:16 AM UTC-4, Richard Smith w= rote:
See http://www.open-st= d.org/jtc1/sc22/wg21/docs/papers/2016/p0289r0.pdf
The paper received some support from evolution. Some felt that = the right answer was to wait for Modules. As noted in the above paper there= are some open questions as to how this would actually work if we went forw= ard with it.

1) I personally wo= uld consider the possibility of declaring pointers of nested=C2=A0classes b= ased on the forward declaration of the aforementioned nested class at all t= imes. Ex.:

class X;
struct X::A;

X::A=C2=A0* p =3D nullptr; // fine

1.1)
class X
{
}; // error=C2=A0caught her= e: missing class A

1.2)
class X
{
=C2=A0 =C2=A0 struct A;
}; // error caught here: pr= ivate member and already used as public

Unless we bring the notion of "partial declarations" and= forward declarations of nested structures are made like this:
class X
{
=C2=A0 =C2=A0 struct A;
=C2=A0 =C2=A0 .... // ellipsis operator here
};

<= /div>
X::A=C2=A0* p =3D nullptr; // error

class X
{
=C2=A0 =C2=A0 struct A;
=C2=A0 =C2=A0=C2=A0
=C2=A0 =C2=A0 void foo()
=C2=A0 = =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 X::A=C2=A0* p =3D nullptr; /= / fine
=C2=A0 =C2=A0 }
};

This way that would solve the access scope problem cleanly.

Regards,
-Phil

--
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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/75fb8736-b92a-480f-9a36-310b3e03b131= %40isocpp.org.
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