SCIP习题 1.21(寻找最小因子)

(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))

(smallest-divisor 199)
(smallest-divisor 1999)
(smallest-divisor 19999)