Test a number for primality.
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| (define (square n) (* n n)) | |
| (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) | |
| (= | |
| n | |
| (smallest-divisor n))) | |
| (define (start-prime-test n start-time) | |
| (if | |
| (prime? n) | |
| (report-prime | |
| (- | |
| (runtime) | |
| start-time)))) | |
| (define (report-prime elapsed-time) | |
| (display " *** \n") | |
| (display elapsed-time) | |
| (display " *** \n") | |
| "over") | |
| (define (timed-prime-test n) | |
| (display n) | |
| (start-prime-test n (runtime))) | |
| (timed-prime-test 2932031007403) |