Path: utzoo!attcan!uunet!zaphod.mps.ohio-state.edu!usc!isi.edu!gremlin!wind.nrtc.northrop.com!kkenny
From: kkenny@wind.nrtc.northrop.com (Kevin B. Kenny KE9TV)
Newsgroups: comp.lang.c++
Subject: Delegation through a pointer
Message-ID: <11578@gremlin.nrtc.northrop.com>
Date: 24 Oct 90 20:01:53 GMT
Sender: news@gremlin.nrtc.northrop.com
Reply-To: ke9tv@nrtc.northrop.com (Kevin B. Kenny KE9TV)
Organization: Northrop Research & Technology Center, Palos Verdes, CA
Lines: 32


In Bjarne Stroustrup's paper, ``Multiple Inheritance for C++,''
Stroustrup discusses an extension of the inheritance mechanism that
allows a class to inherit froman object identified by pointer: i.e.,

------------------------------------------------------------------------
class B {
	int b;
	void f ();
};
class C : public *p {
private:
	B* p;
public:
	C () : p (new B) {};
	C (B* q) : p (q) {};
}
void f (C* q)
{
	q -> f ();		// that is, q -> p -> f ();
}
------------------------------------------------------------------------

This extension never made it into the language.  I'm curious what its
status is: were there insuperable problems with it?  What other way is
provided for the designer of a class B to specify that B wants to
inherit from A *or from any of A's derived classes*?

Kevin Kenny	KE9TV
Northrop Research & Technology Center
Opinions expressed in this article are those of the author, and not
official positions of Northrop Corporation or any of its subsidiaries.