220 6099 article Path: news.gmane.org!not-for-mail From: cornedbee@google.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: Mixins for C++ Date: Mon, 2 Sep 2013 07:24:26 -0700 (PDT) Lines: 152 Approved: news@gmane.org Message-ID: References: <1ff4e759-ddf8-481a-ae5d-33f492e4665d@isocpp.org> <52219447.2070501@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1984_9083185.1378131866915" X-Trace: ger.gmane.org 1378131865 18578 80.91.229.3 (2 Sep 2013 14:24:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 2 Sep 2013 14:24:25 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD43DGWT5IFRBG57SKIQKGQEWBXXGCA@isocpp.org Mon Sep 02 16:24:29 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qe0-f69.google.com ([209.85.128.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VGV3M-0000Ku-MT for gclcip-std-proposals@m.gmane.org; Mon, 02 Sep 2013 16:24:28 +0200 Original-Received: by mail-qe0-f69.google.com with SMTP id 5sf5396576qeb.8 for ; Mon, 02 Sep 2013 07:24:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.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=kfeKo4AQfwunSYJebFU+3kCnKCbw0VJhV4lz/PoO3r0=; b=XUn3hERfkcs1mcwam9YeZEd3dbeYwghmwXUP75QENJCQa86dot3dFceUNm6b0wPNTq bl5umLcR031bqlF62P0DkrKzDkKQ5Z2LmSBfya513u7wcnhG4ikzZ3tvvk/GJUPv5YUs fk3TKPKrWo7G5/btliNXOPwWvvOoy4zDhwtG7lHjW1fZ2x6+WlZH8j/wWZyTKU8lDOSn ZSeHaONaESe8LquYZ/xvkNfrEm2tRwjCOeUtvi4sqDWNeHjqtK/drXAvVQuaeG3wkfJ0 WL/cxukOeV2rjO68Cev//PP7Bldf3IT7FnwTDmFRGfwBKg56OpXc/EpZHfg1aKwm2noi cokw== X-Received: by 10.236.227.165 with SMTP id d35mr151727yhq.51.1378131867832; Mon, 02 Sep 2013 07:24:27 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.1.227 with SMTP id 3ls2359644qep.84.gmail; Mon, 02 Sep 2013 07:24:27 -0700 (PDT) X-Received: by 10.49.25.83 with SMTP id a19mr1012177qeg.1.1378131867299; Mon, 02 Sep 2013 07:24:27 -0700 (PDT) In-Reply-To: <52219447.2070501@wanadoo.fr> X-Original-Sender: cornedbee@google.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:6099 Archived-At: ------=_Part_1984_9083185.1378131866915 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Saturday, August 31, 2013 8:59:19 AM UTC+2, Vicente J. Botet Escriba=20 wrote: > > Le 29/08/13 11:38, corn...@google.com a =E9crit : > =20 > > > On Thursday, August 29, 2013 3:11:47 AM UTC+2, R=F3bert D=E1vid wrote:=20 >> >> >> Consider: >> mixin noncopyable { >> noncopyable(const noncopyable&) =3D delete; >> }; >> struct Foo{ >> using mixin noncopyable; >> }; >> struct Bar : public Foo { >> Bar(const Bar&) : Foo() {} >> } >> Is Bar noncopyable (conflicting with the copy constructor definition,= =20 >> making Bar ill-formed)? >> >> =20 > Bar is well-formed and copyable. > > This seems counter intuitive. If Foo is not copyable, Bar canot be=20 > copyable. > =20 > Why? You just explicitly defined that Bar's notion of copying is to=20 default-construct the Foo part of the object. If you explicitly define the= =20 copy constructor for a class, that class is copyable; everything else would= =20 be highly counter-intuitive. =20 --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. ------=_Part_1984_9083185.1378131866915 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable


On Saturday, August 31, 2013 8:59:19 AM UTC+2, Vic= ente J. Botet Escriba wrote:
=20 =20 =20
Le 29/08/13 11:38, corn...@google.com a =E9crit :


On Thursday, August 29, 2013 3:11:47 AM UTC+2, R=F3bert D=E1vid wrote:

Consider:
mixin noncopyable {
  noncopyable(const noncopyable&) =3D delete;
};
struct Foo{
  using<= /span> mixin noncopyable;
};
struct Bar : public Foo {
  Bar(const Bar&) : Foo() {}
}
Is Bar noncopyable (conflicting with the copy constructor definition, making Bar ill-formed)?


Bar is well-formed and copyable.

This seems counter intuitive. If Foo is not copyable, Bar canot be copyable.
 

Why? You = just explicitly defined that Bar's notion of copying is to default-construc= t the Foo part of the object. If you explicitly define the copy constructor= for a class, that class is copyable; everything else would be highly count= er-intuitive.
 

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