TITLE: Virtual static members


PROBLEM: giszter@globus-pallidus.ai.mit.edu (Simon Giszter)

I have a problem using statics that I need a work around for.
I want a new (different) copy of a static in a derived class.
The goal is to create a class which has a pointer to a 
list of its objects and a derived class with a separate 
pointer to a list of its objects without writing new copies of
all the member functions operating on the base list through
the pointer.


RESPONSE: barmar@think.com (Barry Margolin), 19 Jun 92
	  Thinking Machines Corporation

What you want is frequently referred to as "virtual static members", and
C++ doesn't have them.  However, it's pretty easy to emulate them.

One way would be to use virtual functions to assign and access the
variable.  These would have to be duplicated in each derived class, but
this is better than duplicating *all* the member functions that use the
member.

Another way would be to have a single virtual function that returns a
pointer or reference to the static, and just this one function would have
to be duplicated.