SICP习题 1.22(素数)

(define (next-odd n)
  (if (odd? n)
      (+ 2 n)
      (+ 1 n)))

(define (smallest-divisor n)
  (find-divisor n 2))

(define (find-divisor n test-divisor)
  (cond ((> (square test-divisor) n) n)
        ((divides? n test-divisor) test-divisor)
        (else (find-divisor n (+ test-divisor 1)))))

(define (divides? a b)
  (= (remainder a b) 0))

(define (prime? n)
 (= n (smallest-divisor n)))

(define (square x)
  (* x x))

(define (continue-primes n count)
  (cond ((= count 0) (display "are primes"))
        ((prime? n) (display n)
        (newline)
        (continue-primes (next-odd n) (- count 1)))
        (else (continue-primes (next-odd n) count))))

(continue-primes 1000 10)