[Edu-sig] quantum instance?

[Arthur]

Trying to handle the sudden change of state of an instance of an object 
- a "quantum instance"

c starts as a Circle instance.

Say, in the course of the manipulation of c its radius approaches 
towards infinity, and upon the radius becoming > than some Max, I want c 
to suddenly think of itself as a Line instance rather than as a Circle 
instance.

doable?

hints?

Art