;;; Scheme Recursive Art Contest Entry
;;;
;;; Please do not include your name or personal info in this file.
;;;
;;; Title: "Sierpinski Gasket" -- EE16A HW10 Q3
;;;
;;; Description:
;;;    <EE Sixteen A
;;;    songs are sung of this fractal.
;;;    Sixty One A draws>
;;;   
;;;  

(define (avg a b)
  (/ (+ a b) 2)
)

(define (triangle x1 y1 x2 y2 x3 y3)
  (penup)
  (goto x1 y1)
  (pendown)
  (goto x2 y2)
  (goto x3 y3)
  (goto x1 y1)
)

(define (gasket x1 y1 x2 y2 x3 y3 depth)
 (cond
  ((= depth 0))
  (else
   (triangle x1 y1 x2 y2 x3 y3)
   (gasket (avg x1 x2) y1 x2 y2 (avg x2 x3) (avg y2 y3) (- depth 1))
   (gasket x1 y1 (avg x1 x2) y2 (avg x1 x3) (avg y1 y3) (- depth 1))
   (gasket (avg x1 x3) (avg y1 y3) (avg x2 x3) (avg y2 y3) x3 y3 (- depth 1))
  )
 )
)

(define (draw)
  (speed 0)
  (hideturtle)
  (gasket -500 -450 500 -450 0 (- (* 500 (sqrt 3)) 450) 10)
  (exitonclick))

; Please leave this last line alone.  You may add additional procedures above
; this line.
(draw)