;;; maze.scm    Dave Reed
;;; state space representation of a maze: (row-index col-index)

(define MAZE
  '("*********"
    "S       *"
    "* ** *  *"
    "*   **  *"
    "* * *****"
    "* *     *"
    "*  * ** E"
    "*********"))

(define (GET-MOVES state)
  
  (define (prune-illegal statelist)
    (cond ((null? statelist) '())
          ((or (< (caar statelist) 0) (>= (caar statelist) (length MAZE))
               (< (cadar statelist) 0) (>= (cadar statelist)  (string-length (car MAZE)))
               (equal? (string-ref (list-ref MAZE (caar statelist)) (cadar statelist)) #\*))
           (prune-illegal (cdr statelist)))
          (else (cons (car statelist) (prune-illegal (cdr statelist))))))
  
  (prune-illegal (list (list (- (car state) 1) (cadr state))
                       (list (+ (car state) 1) (cadr state))
                       (list (car state) (- (cadr state) 1))
                       (list (car state) (+ (cadr state) 1)))))
  
 
  
(define (HEURISTIC state goal)
  (- 0 (+ (abs (- (car state) (car goal))) (abs (- (cadr state) (cadr goal))))))