220 38063 <228ebe66-fa3d-40e8-a42f-37de41834977@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Bengt Gustafsson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Fornux C++ Superset - Forward Declarations of Nested Structures Date: Fri, 11 May 2018 07:30:34 -0700 (PDT) Lines: 152 Approved: news@gmane.org Message-ID: <228ebe66-fa3d-40e8-a42f-37de41834977@isocpp.org> References: <34fa23ed-1fab-44d5-92ab-217067b68225@isocpp.org> <75fb8736-b92a-480f-9a36-310b3e03b131@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_10214_285001668.1526049034592" X-Trace: blaine.gmane.org 1526048910 10775 195.159.176.226 (11 May 2018 14:28:30 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 11 May 2018 14:28:30 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCRIRSPDTQIRBDGS23LQKGQEL53WI6I@isocpp.org Fri May 11 16:28:26 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f72.google.com ([209.85.213.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fH922-0002jB-Cj for gclcip-std-proposals@m.gmane.org; Fri, 11 May 2018 16:28:26 +0200 Original-Received: by mail-vk0-f72.google.com with SMTP id b136-v6sf4123406vke.0 for ; Fri, 11 May 2018 07:30:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; 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; bh=sK2x+JHcraJPvEzsLhzfMgBWeWRkVfZAkvI5Y4YNOv0=; b=RHmfn7erc4YDXSzShjdU0hJw6u6e5eUNUtIR3ji1CkpUO71F0pWrClYPIUcPlS/yA4 hDnSnw5e/g5xvMe0V3AO02v45tqTYbkKyjdD9WDODW8Ax6VtZ84GYMSwD/nqAORNFnWc Na8FRWiQ6cP90ZipbO2svuhTtIRnFDj+PcTx2o/JoqqFoJRZQgoqJUKiTNXJDJwjoFJ9 53T3q/MuhvVWDqj1OC9FgPH7nl9cs8xcfDxR7Dxe5zh7EXlp+1Jan+8ZQzUXFa5hjbS6 0vKmV9WSLZNum43RiliBNxVGvB/rbW95ckzF3lUmC3HDXMme0Wv86lBK0GCWz4fR7bcX yWaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; 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:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=sK2x+JHcraJPvEzsLhzfMgBWeWRkVfZAkvI5Y4YNOv0=; b=YvcM+AzJ0M9ICgSz4ynkVW37L0/ZEZ0elIpXwB1famPNOi1/CEKpGj/EyVOrc66Hll 1xaisFkQk1KQ6IlBHyKl6nhhRq6PRgAKWrZ73uLHkV8ksfXUKXc7Mmj9kMP8h9iT/2B3 c67zjXj5ay7e418k0/Hh09r/rm20kPtjFkK9ZWSGYOb3jnjwc1tUKyl9SMr9xbUv4L1B 63ymtso3WDgfoy5qHGdV2k7kC8C3p30+GmRsE7la9P6lISqMkdb8M1baI4j+kKwhOBxP r5oLSxoC9FIYCqic+ibvmUmE+Ci1YUC5FoYRxbaSTuWW2H/Sif7q5JEeEVllM6dDraRL aURg== X-Gm-Message-State: ALKqPwfeJvp8FwJxJTHvpAbB2eMYQgol08UqztMsE2h2Ic+w82XX6p0r T7V6c8otuxH++HrHA5Id5ncjuA== X-Google-Smtp-Source: AB8JxZrxaIDn+xGZiBOldCg5g1CZkzES8uS5Nl8RtQ55eJ6OeY8nDgf24Ye68LSrykAA14snMIdPGw== X-Received: by 2002:a1f:1505:: with SMTP id 5-v6mr1029631vkv.51.1526049037341; Fri, 11 May 2018 07:30:37 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a1f:ab4f:: with SMTP id u76-v6ls274431vke.2.gmail; Fri, 11 May 2018 07:30:36 -0700 (PDT) X-Received: by 2002:a1f:3686:: with SMTP id d128-v6mr244585vka.7.1526049035351; Fri, 11 May 2018 07:30:35 -0700 (PDT) In-Reply-To: X-Original-Sender: bengt.gustafsson@beamways.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:38063 Archived-At: ------=_Part_10214_285001668.1526049034592 Content-Type: multipart/alternative; boundary="----=_Part_10215_1712949569.1526049034593" ------=_Part_10215_1712949569.1526049034593 Content-Type: text/plain; charset="UTF-8" I'm skeptical to partial declarations as the rules would be quite complicated. What I have found lacking on various occasions is the ability to declare inheritance in a forward declaration. Being able to declare inheritance relations early reduces the need of moving method implementations of methods out of the class head in certain situations. When it comes to friend declarations it seems that you would not be helped by including them in a forward declaration as their sole purpose is to allow access to private members _which have not been declared yet_. I would favor a proposal which includes your initial possibility to declare a nested class after declaring the outer class (or for consistence with namespace A::B { ... } without having to do so) plus the possibility to declare inheritance in a forward declaration. Den fredag 11 maj 2018 kl. 01:03:36 UTC+2 skrev Phil Bouchard: > > On 05/02/2018 07:26 AM, Phil Bouchard wrote: > > 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. > > Do we all agree this is a good solution? This could provide friend > declarations as well: > > class X > { > friend struct A; > > struct A; > .... // ellipsis operator here > }; > > > 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/228ebe66-fa3d-40e8-a42f-37de41834977%40isocpp.org. ------=_Part_10215_1712949569.1526049034593 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I'm skeptical to partial declarations as the rules wou= ld be quite complicated. What I have found lacking on various occasions is = the ability to declare inheritance in a forward declaration. Being able to = declare inheritance relations early reduces the need of moving method imple= mentations of methods out of the class head in certain situations.

=
When it comes to friend declarations it seems that you would not= be helped by including them in a forward declaration as their sole purpose= is to allow access to private members _which have not been declared yet_.<= /div>

I would favor a proposal which includes your initi= al possibility to declare a nested class after declaring the outer class (o= r for consistence with namespace A::B { ... } without having to do so) plus= the possibility to declare inheritance in a forward declaration.


Den fredag 11 maj 2018 kl. 01:03:36 UTC+2 skrev Phil Bouchard:On 05/02/2018 07:26 AM, Phil Bouch= ard wrote:
> Unless we bring the notion of "partial declarations" and= forward=20
> declarations of nested structures are made like this:
>=20
> class X
> {
> =C2=A0=C2=A0 =C2=A0 struct A;
> =C2=A0=C2=A0 =C2=A0 .... // ellipsis operator here
> };
>=20
> X::A=C2=A0* p =3D nullptr; // error
>=20
> class X
> {
> =C2=A0=C2=A0 =C2=A0 struct A;
> =C2=A0=C2=A0 =C2=A0 void foo()
> =C2=A0=C2=A0 =C2=A0 {
> =C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 X::A=C2=A0* p =3D nullptr; // fi= ne
> =C2=A0=C2=A0 =C2=A0 }
> };
>=20
> This way that would solve the access scope problem cleanly.

Do we all agree this is a good solution? This could provide friend=20
declarations as well:

class X
{
=C2=A0 =C2=A0 =C2=A0 friend struct A;

=C2=A0 =C2=A0 =C2=A0 struct A;
=C2=A0 =C2=A0 =C2=A0 .... // ellipsis operator here
};


Regards,
-Phil

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/228ebe66-fa3d-40e8-a42f-37de41834977= %40isocpp.org.
------=_Part_10215_1712949569.1526049034593-- ------=_Part_10214_285001668.1526049034592-- .