220 32783 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?Q?Klaim_=2D_Jo=C3=ABl_Lamotte?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: The Proxies - A Language Feature Decoupling Implementations from Requirements of Polymorphism Date: Fri, 16 Jun 2017 18:16:22 +0200 Lines: 108 Approved: news@gmane.org Message-ID: References: <8d79a013-fe0e-4fb6-8278-d438ae9b4c64@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="94eb2c12295a32b37f0552161b0f" X-Trace: blaine.gmane.org 1497629785 2354 195.159.176.226 (16 Jun 2017 16:16:25 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 16 Jun 2017 16:16:25 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD3NR2WQQ4IBBV4ISDFAKGQETZZ7ZLI@isocpp.org Fri Jun 16 18:16:21 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qt0-f198.google.com ([209.85.216.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dLtv1-0000N9-KY for gclcip-std-proposals@m.gmane.org; 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[2607:f8b0:400c:c08::22f]) by mx.google.com with ESMTPS id z186si886719vkg.271.2017.06.16.09.16.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Jun 2017 09:16:23 -0700 (PDT) Received-SPF: pass (google.com: domain of mjklaim@gmail.com designates 2607:f8b0:400c:c08::22f as permitted sender) client-ip=2607:f8b0:400c:c08::22f; Original-Received: by mail-ua0-x22f.google.com with SMTP id 68so28404653uas.0 for ; Fri, 16 Jun 2017 09:16:23 -0700 (PDT) X-Received: by 10.176.6.105 with SMTP id f96mr7423975uaf.15.1497629782616; Fri, 16 Jun 2017 09:16:22 -0700 (PDT) Original-Received: by 10.31.169.82 with HTTP; Fri, 16 Jun 2017 09:16:22 -0700 (PDT) In-Reply-To: <8d79a013-fe0e-4fb6-8278-d438ae9b4c64@isocpp.org> X-Original-Sender: mjklaim@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.b=VBAmn9Yy; spf=pass (google.com: domain of mjklaim@gmail.com designates 2607:f8b0:400c:c08::22f as permitted sender) smtp.mailfrom=mjklaim@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=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:32783 Archived-At: --94eb2c12295a32b37f0552161b0f Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On 13 June 2017 at 15:49, Mingxin Wang wrote: > *Class template proxy* > > Expression "proxy" is a well-formed type if I is a pure virtual > class (without a virtual destructor) and W is a type meets the Wrapper > requirements defined above. > > "proxy" is MoveConstructible if W is MoveConstructible, while > "proxy" is CopyConstructible if W is CopyConstructible. > > Providing p is a value of "proxy" and i is a pointer of I, > "p.f(args...)" shall be a valid expression if "(*i).f(args...)" is a vali= d > expression, where f is any valid function name (including operator > overloads) and "args..." is any valid combination of values of any type. > Could you clarify: if a system want to take anything that have the interface described by I, how should it some_system.take_it_and_do_something( ??? object ); I believe this would be really too restrictive: some_system.take_it_and_do_something( proxy object ); Because it would force the user code to use only one ownership strategy for anything passed to this function. In my experience, I want the system to ignore if it will own or not the object, let the user decide, as long as the proxy is usable as a normal object. In my opinion, the fact that the real object is shared or not should not be imposed by the system consuming the proxy. Jo=C3=ABl Lamotte --=20 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 e= mail 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/CAOU91OO5iXoZ1Hf%3Dq7Ux%3DBuH9C_fFfUz_%3Dxt3DWEA= JbrhzOzhA%40mail.gmail.com. --94eb2c12295a32b37f0552161b0f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

= On 13 June 2017 at 15:49, Mingxin Wang <wmx16835vv@163.com>= wrote:
Class template proxy

Express= ion "proxy<I, W>" is a well-formed type if I is a pure virt= ual class (without a virtual destructor) and W is a type meets the Wrapper = requirements defined above.

"proxy<I, W>= ;" is MoveConstructible if W is MoveConstructible, while "proxy&l= t;I, W>" is CopyConstructible if W is CopyConstructible.
=
Providing p is a value of "proxy<I, W>" and = i is a pointer of I, "p.f(args...)" shall be a valid expression i= f "(*i).f(args...)" is a valid expression, where f is any valid f= unction name (including operator overloads) and "args..." is any = valid combination of values of any type.


Could you clarify: if a system wa= nt to take anything that have the interface described by I, how should it= =C2=A0

=C2=A0 =C2=A0 some_system.take_it_and_do_something( ??? object );

I believe this= would be really too restrictive:

=C2=A0 =C2=A0 some_system.take_it_and_do_someth= ing( proxy<I,W> object );

<= div class=3D"gmail_extra">Because it would force the user code to use only = one ownership strategy for anything passed to this function.
In my experience, I want the system to ignore if it will = own or not the object, let the user decide, as long as
the proxy is usable as a normal object.
In my opinion, the fact that the real object is shared or not shou= ld not be imposed by the system consuming the proxy.

Jo=C3=ABl Lamotte

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