From 3296905696593016486 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,8a4cd038fc33ea5a X-Google-Attributes: gidf78e5,public From: clamage@Eng.Sun.COM (Steve Clamage) Subject: Re: Ambiguous conversion due to private ba Date: 1998/03/25 Message-ID: <6f9nbr$sg5@engnews1.Eng.Sun.COM>#1/1 X-Deja-AN: 337686738 Approved: Fergus Henderson References: <3517FB6C.6DE8@central.beasys.com> X-Original-Date: 25 Mar 1998 01:41:15 GMT Organization: Sun Microsystems Inc. X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBFAgUANRmLDOEDnX0m9pzZAQFBvwF/d5HIfS8cJu1C+Hg3MZDqstNyjxh/nZ1H dQLIftKgggQc5gUbRCj95oVvKlwv6SPf =b6ZW Reply-To: clamage@Eng.Sun.COM Newsgroups: comp.std.c++ In article 6DE8@central.beasys.com, David R Tribble writes: >jkanze@otelo.ibmmail.com wrote: >> ... >> But doesn't this sort of >> defeat the purpose of private inheritance? Private inheritance isn't >> meant to represent an isA relationship. > >Huh? Inheritance does mean an IsA relationship, private or >otherwise. Or does C++ grant some special meaning to private >inheritance that doesn't apply to inheritance in general? The IsA relationship means that you can use a Derived any place a Base was expected. When you use private inheritance, that property doesn't hold. In addition, private inheritance means the base class interface is not usefully part of the derived class interface. Example: class Base { public: void f(); ... }; class Derived : private Base { ... }; void foo(Base&); Base b; ... Derived d; foo(d); // error, no implicit conversion to Base& b = d; // error, cannot assign Derived to Base d.f(); // error, f is not accessible Thus, private inheritance fails any test of the IsA relationship. --- Steve Clamage, stephen.clamage@sun.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]