(define get-maze
'(
(w w w w w w w)
 (w 0 0 1 1 w w)
(w w 0 1 1 0 w)
 (w w w w w w w)
)
)

(define program
  '(
    (procedure add
      (sub-one turn-180 go turn-right step turn-right turn-right 
       add-one turn-180 go turn-left turn-left  step turn-left 
       add
      )
    )
    (procedure add-one
      (if mark?
          (get-mark step add-one turn-180 step turn-180)
          (put-mark)
      )
     )
    (procedure sub-one
      (if mark?
          (get-mark)
          (put-mark step sub-one turn-180 step turn-180)
      )
     )
    (procedure turn-180
      (turn-left turn-left turn-left)
     )
    (procedure turn-right
      (turn-left turn-left turn-left turn-left turn-left)
     )
    (procedure go
      (if wall? () (step go))
    )
  )
)
(newline)
(simulate (list get-maze (list 4 1) 'west) 'add program 100)