(define (object)
	(define super 'nil)
	(define self 'nil)
	(define (set-self!) (lambda (s) (set! self s)))
	(define (internal m)
		(cond
			((eq? m 'type) (lambda () 'object))
			((eq? m 'info) (lambda () (list (send self 'type))))
			((eq? m 'set-self!) (set-self!))
		  (else (lambda args (display (string-append "Message not understood: " (symbol->string m) "\n"))))
		)
	)
	internal
)

(define (point x y)
	(define super (object))
	(define self 'nil)
	(define (set-self!) (lambda (s)
		 (set! self s)
		 (method-lookup super (list 'set-self! s))
	))
  (define (getx) (lambda () x))
  (define (gety) (lambda () y))
  (define (type) (lambda () 'point))
  (define (setx!) (lambda (nx) (set! x nx)))
  (define (sety!) (lambda (ny) (set! y ny)))
  (define (info) (lambda () (append ((super 'info)) (list x))))
  (define (add) (lambda (p)
                  (let ((px ((p 'getx)))
                        (py ((p 'gety))))
                    (point (+ x px) (+ y py))
                   )
                 ))
  (define (sub) (lambda (p)
                  (let ((px ((p 'getx)))
                        (py ((p 'gety))))
                    (point (- x px) (- y py))
                   )
                 ))

  (define (internal m)
    (cond ((eq? m 'set-self!) (set-self!))
          ((eq? m 'type) (type))
					((eq? m 'getx) (getx))
          ((eq? m 'gety) (gety))
          ((eq? m 'setx!) (setx!))
          ((eq? m 'sety!) (sety!))
          ((eq? m 'info) (info))
          ((eq? m 'add) (add))
          ((eq? m 'sub) (sub))
		      (else (lambda args (method-lookup super (list m args))))
		)
	)
  internal
 )

(define (color-point x y color)
	(define super (point x y))
	(define self 'nil)
	(define (set-self!) (lambda (s)
		 (set! self s)
		 (method-lookup super (list 'set-self! s))
	))
	(define (type) (lambda () 'color-point))
	(define (get-color) (lambda () color))
	(define (info) (lambda () (append ((super 'info)) (list color))))
  (define (add) (lambda (p)
                  (let ((px ((p 'getx)))
                        (py ((p 'gety))))
                    (color-point (+ x px) (+ y py) color)
                   )
                 ))
  (define (sub) (lambda (p)
                  (let ((px ((p 'getx)))
                        (py ((p 'gety))))
                    (color-point (- x px) (- y py) color)
                   )
                 ))

	(define (internal m)
		(cond ((eq? m 'set-self!) (set-self!))
					((eq? m 'type) (type))
					((eq? m 'get-color) (get-color))
					((eq? m 'info) (info))
					((eq? m 'add) (add))
		      (else (lambda args (method-lookup super (cons m args))))
		)
	)
	internal
)

(define (method-lookup reciever message)
  (if (= (length message) 1)
      ((reciever (car message)))
      ((reciever (car message)) (car (cdr message)))
  ))

(define (send reciever . message)
  (if (procedure? reciever)
      (method-lookup reciever message)
      (display (string-append "Inappropriate receiver object: " (symbol->string reciever) "\n"))
  )
 )

(define (new cls . args)
	(let ((object (apply cls args)))
		(send object 'set-self! object)
		object
	)
)

(define cp (new color-point 5 6 'red))
(send cp 'type) ; color−point
(send cp 'getx) ; 5
(send cp 'gety) ; 6
(send cp 'get-color) ; red
(send cp 'info) ; (color−point 5 6 red