220 10673 article Path: news.gmane.org!not-for-mail From: Richard Smith Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Forward declaring names Date: Fri, 16 May 2014 16:37:23 -0700 Lines: 117 Approved: news@gmane.org Message-ID: References: <20140509221552.GA32099@sara.home> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=047d7b6dc67a3bc16204f98ce5bd X-Trace: ger.gmane.org 1400283457 6667 80.91.229.3 (16 May 2014 23:37:37 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 16 May 2014 23:37:37 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDVNBJG4YAIBBM6C3KNQKGQELT5SHHQ@isocpp.org Sat May 17 01:37:30 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ve0-f199.google.com ([209.85.128.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WlRgr-00056l-8f for gclcip-std-proposals@m.gmane.org; Sat, 17 May 2014 01:37:25 +0200 Original-Received: by mail-ve0-f199.google.com with SMTP id oz11sf12535576veb.10 for ; Fri, 16 May 2014 16:37:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=lgF5I2ExpJAeAjsRe1EpKti4DWlvmatzxLdKFFkGUlg=; b=g4IHbdDnpwPmX6qrp69K/ZReSsMDcn92knO/VUuiwDj5cY7nLTsk02mjqLG0LQydvc foRPQ/pGAEyjUrNzT/uT1slIMjRmCgSfxW4nxjFuWXwcd1dMKlHRPd5eq5E63LjnqVvE IOvqM3pgqUo83WnOoq5AeAXyfk64Jj2FzT27NU4yZnpazz7wMWL9vIyWLyd7EHjFxnHu JjFTce9Yh1LD9J9zED9jJevAXQ1Ibenf1RlHGO6V16zb7BnfeC0gpdMgKgWpJB7J9TFx jVC4tJ5S8e1BLNfafr3ReG2AXrRqFvN3LmS4f0RZ50ts0LVMBuhKiqf9YvxE2J/8BSnF 55SA== X-Gm-Message-State: ALoCoQngPL/0TQftJuFRixHWgBNRnC7zEG5a/uwhj9H54TQMaAtqZZ0FxHWdPoivWxbkUjtiCMxz X-Received: by 10.224.147.72 with SMTP id k8mr8882657qav.5.1400283444325; Fri, 16 May 2014 16:37:24 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.25.171 with SMTP id 40ls929031qgt.85.gmail; Fri, 16 May 2014 16:37:23 -0700 (PDT) X-Received: by 10.221.26.10 with SMTP id rk10mr16785639vcb.0.1400283443728; Fri, 16 May 2014 16:37:23 -0700 (PDT) Original-Received: from mail-ve0-x235.google.com (mail-ve0-x235.google.com [2607:f8b0:400c:c01::235]) by mx.google.com with ESMTPS id b4si2016534vck.7.2014.05.16.16.37.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 16 May 2014 16:37:23 -0700 (PDT) Received-SPF: pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c01::235 as permitted sender) client-ip=2607:f8b0:400c:c01::235; Original-Received: by mail-ve0-f181.google.com with SMTP id pa12so3871878veb.26 for ; Fri, 16 May 2014 16:37:23 -0700 (PDT) X-Received: by 10.58.198.107 with SMTP id jb11mr16835948vec.10.1400283443477; Fri, 16 May 2014 16:37:23 -0700 (PDT) Original-Sender: metafoo@gmail.com Original-Received: by 10.58.218.131 with HTTP; Fri, 16 May 2014 16:37:23 -0700 (PDT) In-Reply-To: X-Original-Sender: richard@metafoo.co.uk X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c01::235 as permitted sender) smtp.mail=metafoo@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:10673 Archived-At: --047d7b6dc67a3bc16204f98ce5bd Content-Type: text/plain; charset=UTF-8 On Fri, May 16, 2014 at 4:16 PM, wrote: > > On Saturday, May 17, 2014 10:36:44 AM UTC+12, Richard Smith wrote: > >> On Fri, May 16, 2014 at 2:41 PM, Stack Machine wrote: >> >>> Forward declarations are a stupid idea to begin with and should not be >>> expanded on. The solution to this should be Modules. >>> >> >> I generally agree, but with just a pinch of caution: forward declarations >> serve two purposes: reducing include dependencies and breaking cycles. >> Modules only helps with the first problem; we still need forward >> declarations for the second problem. >> > > How about: > > auto HANDLE; > Something like 'typename HANDLE;' would probably be more appropriate, since this is a type, not a variable. void (HANDLE& x); > > Meaning: "Hey compiler HANDLE might be a class, struct, typedef, or > whatever, but if you don't need to know, just go with it knowing it's not a > spelling mistake." > > Is that what the OP wanted, and would it work? > I can't answer the first half of this question =) Yes, this could work, but the type would need to be properly-declared before you could define or call this function, so it's not clear to me how useful this would be. (This level of opaqueness goes beyond being a merely incomplete type, since you don't even know how to represent a pointer or reference to the type.) -- --- 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/. --047d7b6dc67a3bc16204f98ce5bd Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On F= ri, May 16, 2014 at 4:16 PM, <gmisocpp@gmail.com> wrote:

On Saturday, May 17, 2014 10:36:44 AM UTC+12, Richard = Smith wrote:
On Fri, May 16, 2014 at 2:= 41 PM, Stack Machine <stackm...@hotmail.com>= wrote:
Forward declarations are a stupid idea to= begin with and should not be expanded on. The solution to this should be M= odules.

I generally agree, but with just a pinch o= f caution: forward declarations serve two purposes: reducing include depend= encies and breaking cycles. Modules only helps with the first problem; we s= till need forward declarations for the second problem.

How about:

auto HANDLE;

= Something like 'typename HANDLE;' would probably be more appropriat= e, since this is a type, not a variable.

void (H= ANDLE&=C2=A0x);=C2=A0

Meaning: "Hey = compiler=C2=A0HANDLE=C2=A0might be=C2=A0a class, struct, typedef, or whatev= er, but=C2=A0if you don't need to know, just go with it knowing it'= s not a spelling mistake."

Is that what the OP wanted, and would it work?

I can't answer the first half= of this question =3D)

Yes, this could work, but t= he type would need to be properly-declared before you could define or call = this function, so it's not clear to me how useful this would be. (This = level of opaqueness goes beyond being a merely incomplete type, since you d= on't even know how to represent a pointer or reference to the type.)

--

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