gistfile1.txt

#lang racket
(require racket/draw)

(define bm (make-bitmap 640 480))
(define dc (send bm make-dc))
(define pixs (make-hash))

(define black (make-object color% 0 0 0))
(define (plot row col)
  (hash-set! pixs (list col row) 1)
  (send dc set-pixel col row black))

(define (pick row col)
  (hash-ref pixs (list col row) 0))
  
(define (is_on_next_gen row col)
  (not (equal? (pick (- row 1) (- col 1))
               (pick (- row 1) (+ col 1)))))

(define (compute_row (gen 1) (start 319) (end 321))
  (when (is_on_next_gen gen start) (plot gen start))
  (cond [(= start end)
         (compute_row (+ 1 gen) (- 319 gen) (+ 321 gen))]
        [(= gen 128)
         (void)]
        [else
         (compute_row gen (+ 1 start) end)]))

(time (plot 0 320))
(time (compute_row))
(time bm)