; mutation and aliasing

(define back-rotate (p) ; p:Point
    ; MODIFIES: p
    ; EFFECT: rotate p -90 degrees
    (begin
	(Point$rotate p)
	(Point$rotate p)
	(Point$rotate p)))

(define start_up ()
  (begin
    (set p1 (Point$new 3 5))
    (set p2 p1)

    (Point$reflect p1)

    (print (Point$abscissa p2))
    (print (Point$ordinate p2))

    (back-rotate p1)

    (print (Point$abscissa p2))
    (print (Point$ordinate p2))

    (print (Point$abscissa p2))
    (print (Point$ordinate p2))))