;;; Scheme Recursive Art Contest Entry
;;;
;;; Please do not include your name or personal info in this file.
;;;
;;; Title: << "" 1 6 FOR I RAND 26 * IP "A" NUM + CHR + NEXT >>
;;;
;;; Description:
;;;   Out of randomness,
;;;   an image emerges.
;;;   Yours to interpret.

(define (draw)
  ()
  (exitonclick))

;;; insecure LCG implemented below
(define seed 23298572)
(define m (expt 2 32))
(define a 1103515245)
(define c 12345)

(define (rand seed) (modulo (+ (* a seed) c) m))
(define (lindex lst index) (if (eq? index 0) (car lst) (lindex (cdr lst) (- index 1))))
(define (fact x) (if (eq? x 0) 1 (* x (fact (- x 1)))))
(define (comb n k) (/ (fact n) (* (fact k) (fact (- n k)))))
(define (evalbezier points order u term)
	(if (> term order) 0 (+ (* (lindex points term) (comb order term) (expt (- 1 u) (- order term)) (expt u term)) (evalbezier points order u (+ term 1)))))
(define (plotbezier points_x points_y order u)
	(if (< u 1)
		(begin
			(goto (evalbezier points_x order u 0) (evalbezier points_y order u 0))
			(pd)
			(goto (evalbezier points_x order (+ u 0.05) 0) (evalbezier points_y order (+ u 0.05) 0))
			(pu)
			(plotbezier points_x points_y order (+ u 0.05)))))
(define (makepoints n low high seed)
	(if (eq? n 0)
		nil
		(begin (define seed (rand seed)) (cons (+ (modulo seed (- high low)) low) (makepoints (- n 1) low high seed)))))
(pu)
(begin_fill)
(print (makepoints 10 -100 100 seed))
(define x_pts (makepoints 50 -500 500 seed))
(define seed (lindex x_pts (- (length x_pts) 1)))
(define y_pts (makepoints 50 -500 500 seed))
(define seed (lindex y_pts (- (length x_pts) 1)))
(define x_pts (append x_pts (makepoints 50 -500 500 seed)))
(define seed (lindex x_pts (- (length x_pts) 1)))
(define y_pts (append y_pts (makepoints 50 -500 500 seed)))
(plotbezier x_pts y_pts 9 0)
(end_fill)
; Please leave this last line alone.  You may add additional procedures above
; this line.
(draw)