1.2.6-search-divisor.rkt

#lang sicp
(define (smallest-divisor n)
        (find-divisor n 2))

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

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

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