Comp 272 Program 6	Dordal	April 17, 2001 	Due: May 4, 2001
(May 4 is the date of the final; programs will be accepted through May 7.)

You are to create a copy ctor, a dtor, and an assignment operator
for the shape Group class.  Do *not* do the equality operator 
that was mentioned in a previous version.  The dtor should
properly deallocate all the space used. The copy ctor and operator=
should allow the following (assuming group g1 has been created):
	Group g2 = g1;		// initialization
	Group g3;
	g3 = g1;		// true assignment
	g1.move(x,y);
and now g2 and g3 should *not* have moved.

For the dtor, you simply need to call delete on every pointer in _shapelist;
this will automatically call the Group dtor (~Group) on each subgroup.
When delete is called on a pointer, the dtor of the pointed-to object
is invoked on the thing pointed to; see "Destruction and Deletion"
on page 365 of Horstmann. Because of this principle, if you have
a tree of Groups and subGroups then the subGroups will be deallocated
recursively.

In effect you will presume that pointers are never shared.
This you can enforce with operator= (by making sure that the
new copy of the Group doesn't share pointers with the old),
but cases such as the following can get you in trouble:

	Group g1, g2;
	Shape * p = new Rectangle (....);
	g1.add(p);
	g2.add(p);	// now g1 and g2 share p!

You can fix this with clone(), by making the second
	g2.add(p->clone()).

What could happen if you don't do this?

For the equality operator, you can do one of two things.
THe first is to define a virtual operator== function on 
shapes generally, in which case Group::operator== just checks
that all the subshapes have the same typeid and, if so, compares them.
Or you can just define operator== for Groups, and rely on the 
built-in version for any non-Group shape objects. You will still
use typeid on each pair of corresponding items in _shapelist,
but you will also check the typeid value to see if it is typeid(Group),
in which case you will invoke the Group version.