;;; helper functions: 

;; mid-point : posn posn  ->  posn
;; to compute the mid-point between a-posn and b-posn
(define (mid-point a-posn b-posn)
  (make-posn
    (mid (posn-x a-posn) (posn-x b-posn))
    (mid (posn-y a-posn) (posn-y b-posn))))

;; mid : number number  ->  number
;; to compute the average of x and y
(define (mid x y)
  (/ (+ x y) 2))

;; distance: posn posn -> number
;; to compute the distance between two positions
(define (distance posn1 posn2)
  (sqrt  (+ (* (- (posn-x posn1) (posn-x posn2)) (- (posn-x posn1) (posn-x posn2)))
            (* (- (posn-y posn1) (posn-y posn2)) (- (posn-y posn1) (posn-y posn2)))))
)

;;; more helper functions? 

;; sierpinski : posn posn posn  ->  true
;; to draw a Sierpinski triangle at a, b, and c




(define A (make-posn 200 0))
(define B (make-posn 27 300))
(define C (make-posn 373 300))

(start 400 400)
  
;(sierpinski A B C)