(define (point x y)
 (let ((x x) 
       (y y)
      )

   
;;; Accessors
      (define (getx) x)

      (define (gety) y)

      (define (add p) 
    (point 
     (+ x (send 'getx p))
     (+ y (send 'gety p))))

      (define (type-of) 'point 
   )
     
   (define (self message)
     (cond ((eqv? message 'getx) getx)
           ((eqv? message 'gety) gety)
           ((eqv? message 'add)  add)
           ((eqv? message 'type-of) type-of)
	   (else (error "Undefined message" message))))
     
   self))

 
(define (fac n)
 (if (= n 0) 1 (* n (fac (- n 1)))))