towers of hanoi, simulated
in Scheme
- evaluating (move-tower size from to extra) causes the sequence of moves to be displayed
- example
(move-tower 3 1 3 2)
move top disk from 1 to 3
move top disk from 1 to 2
move top disk from 3 to 2
move top disk from 1 to 3
move top disk from 2 to 1
move top disk from 2 to 3
move top disk from 1 to 3