Newsgroups: comp.std.c++
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!lavaca.uh.edu!menudo.uh.edu!st12a
From: st12a@menudo.uh.edu (richard henderson~)
Subject: Pure functions and derived classes
Message-ID: <1991Apr18.233753.26738@menudo.uh.edu>
Keywords: Pure functions
Sender: st12a@menudo.uh.edu (richard henderson~)
Organization: University of Houston
Date: Thu, 18 Apr 1991 23:37:53 GMT

In the following construction:

struct Base
{
	virtual int func_a() = 0;
	virtual int func_b() = 0;
	virtual int func_c() = 0;
};

struct Mid_a : virtual public Base
{
	virtual int func_a();
	virtual int func_b() = 0;
	virtual int func_c() = 0;
};

struct Mid_b : virtual public Base
{
	virtual int func_a() = 0;
	virtual int func_b();
	virtual int func_c() = 0;
};

struct Der : public Mid_a, public Mid_b
{
	virtual int func_c();
};

both BC++ and g++ complain that the pure functions Mid_a::func_b() and
Mid_b::func_a() are not overridden.

What is the proper way to declare this construction?  It seemed to me
that Mid_a::func_a() should override Mid_b::func_a() and vice-versa.

thanks in advance,
richard~
st12a@menudo.uh.edu
richard@stat.tamu.edu