;; distP : Posn Posn -> Number
;; computes distance between two points
(define (distP p1 p2)
  (sqrt (+ (sqr (- (posn-x p1) (posn-x p2)))
           (sqr (- (posn-y p1) (posn-y p2))))))

;; Examples/tests
(= (distP (make-posn 0 0) (make-posn 5 12)) 13)
(= (distP (make-posn 1 2) (make-posn 4 6)) 5)

;; To run the rest of this, uncomment the appropriate code and use teachpack draw.ss

;; create a canvas
;(start 300 300)

;; demonstrates a way that Posns can be generated interactively
;(wait-for-mouse-click)

;; demonstrates how such Posns can be generated and passed to a useful function
;(distP (wait-for-mouse-click) (wait-for-mouse-click))