Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!world!wmm
From: wmm@world.std.com (William M Miller)
Newsgroups: comp.lang.c++
Subject: Re: Abstract Base Class Enforcement
Keywords: class, abstract, c++
Message-ID: <1991Mar25.154219.4248@world.std.com>
Date: 25 Mar 91 15:42:19 GMT
References: <358@intertel.UUCP> <1991Mar24.204943.9998@world.std.com> <1991Mar25.064202.11497@lth.se>
Organization: The World Public Access UNIX, Brookline, MA
Lines: 16

dag@control.lth.se (Dag Bruck) writes:
> >Actually, you'd need to make *all* the constructors either protected or
> >private.
>
> You may want to keep the copy-constructor public.

No.  Remember that the goal was to make an abstract base class, i.e., a
class of which there could be no objects.  Therefore you can't have by-value
arguments and other contexts in which a copy constructor might be invoked;
the only way a copy constructor can be legitimately invoked for an abstract
base class is from the copy constructor of a derived class, copying the base
class subobject of a derived class object, and protected access is
sufficient for this case.

-- William M. Miller, Glockenspiel, Ltd.
   wmm@world.std.com