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#lang racket
(require racket/pretty)
(require sicp)
(define (next n)
(if (= n 2) 3 (+ n 2)))
(define (find-divisor n test-divisor)
(cond ((> (square test-divisor) n) n)
((divides? test-divisor n) test-divisor)
(else (find-divisor n (next test-divisor)))))
(define (smallest-divisor n)
(find-divisor n 2))
(define (square x) (* x x))
(define (divides? a b)
(= (remainder b a) 0))
(define (prime? n)
(= n (smallest-divisor n)))
(define (report-prime n t duration)
(print n)
(println " *** prime")
(println duration)
t)
(define (start-prime-test n start-time)
(if (prime? n)
(report-prime n true (- (current-inexact-milliseconds) start-time))
false))
(define (time-prime-test n)
(start-prime-test n (current-inexact-milliseconds)))
(define (search-for-primes found n)
(cond
((> found 2) "found three primes")
((time-prime-test n) (search-for-primes (+ found 1) (+ n 2)))
(else (search-for-primes found (+ n 2)))))
(println " *** search for primes")
(search-for-primes 0 1001)
(println " *** search for primes")
(search-for-primes 0 10001)
(println " *** search for primes")
(search-for-primes 0 100001)
(println " *** search for primes")
(search-for-primes 0 1000001)
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