; returns a list of numbers parsed from the first line of the file,
; separated by commas
(define (read-comma-separated-numbers file)
  (let loop [(draws '()) (n 0)]
    (let [(c (get-char file))]
      (cond
	[(char=? c #\,) (loop (cons n draws) 0)]
	[(char-whitespace? c) (reverse (cons n draws))]
	[else (loop draws (+ (* n 10) (string->number (string c))))]))))

; returns numbers 0 to 9 from ascii character
(define (char->number c)
  (- (char->integer c) 48)) ; 48 is ASCII's number zero