gistfile1.scm

(define (is-prime n)
  (if (<= n 3)
    (>= n 2)
  (if (or (= (modulo n 2) 0) (= (modulo n 3) 0))
    #f
  (do ((i 5 (+ i 6))) ((> i (+ (sqrt n) 1)))
    (if (or (= (modulo n i) 0) (= (modulo n (+ i 2)) 0))
      #f))) #t))

(define (main args)
  (display (is-prime 2)))