This example creates several actors that pass a Ball between them.
Each actor first registers itself to be notified when a Ball appears
in the space with a name equal to the actor's name.
When an actor receives a notification, it takes the ball from the
space and puts it back with ball.name set to the next actor.
The last actor passes the ball back to the first actor.
This example creates several actors that pass a Ball between them. Each actor first registers itself to be notified when a Ball appears in the space with a name equal to the actor's name. When an actor receives a notification, it takes the ball from the space and puts it back with ball.name set to the next actor. The last actor passes the ball back to the first actor.