; Solves the problem of the towers of Hanoi.
; Alejandro Luque, 1999

; You may change this function to make it do whatever you want.  
(defun move_disk (from to)
 (msg "Move " from " to " to t)
)

; The actual function that solves the problem.
(defun real_hanoi (n from to aux)
 (cond 
  ((equal n 1) (move_disk from to))
  (t (prog nil
      (real_hanoi (sub1 n) from aux to)
      (move_disk from to)
      (real_hanoi (sub1 n) aux to from)
     )
  )
 )
)

; The function you invoke.
(defun hanoi (n) (real_hanoi n 'a 'b 'c))

(msg "Type (hanoi n) to solve the Hanoi towers problem of order n" t)