;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;; Knowledge Representation and Reasoning CSC 486/2506, Fall 2006
;;
;; Sample file for exercise 4, assignment 1 (Scheme implementation)
;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%




;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;; (solve_tab_sat C): C is a list of clauses where each clause is a 
;;                    list of literals.
;;
;; for instance this is possible clause where literals are
;; represented with integers:
;;
;;      ((1 -2) (2 -8) (-5 -4 3) (5) (4 -2 -6))
;;
;; YOU SHOULD IMPLEMENT THIS FUNCTION. THE PREDICATE SHOULD PRINT
;; "YES" IF C IS SATISFIABLE AND "NO" OTHERWISE
;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

;; this implementation only prints the set of clauses, you should
;; implement your program here.
;;
(define (solve_horn_sat c) 
  (display c)
)








;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;;          OBS: You should not modify anything below 
;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;; (hornsat File): takes a file name, reads its clauses and calls
;;                solve_horn_sat/1 with such set of clauses
;;
;;
;; This should work under MIT Scheme (tested)
;;
;; DO NOT CHANGE
;;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

(define (hornSat filename)
  (let ((idfile (open-input-file filename)))
    (solve_horn_sat (read-list idfile))))

(define (read-list idfile)
  (let ((p (read idfile)))
    (if (equal? p '(end))
	'()
	(cons p (read-list idfile)))))