sicp练习 1.22
(define (square x) (* x x))(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))(define (search-for-primes start-num end-num) (search-for-primes-iter start-num end-num (runtime)))(define (search-for-primes-iter start-num end-num start-time) (cond ((< start-num end-num) (begin (prime? start-num) (search-for-primes-iter (+ start-num 1) end-num start-time))) ((= start-num end-num) (begin (prime? start-num) (newline) (display "all over time: ") (display(- (runtime) start-time)) (newline) (- (runtime) start-time)))));(search-for-primes 1000000 1000100);(search-for-primes 10000000 10000100);(search-for-primes 100000000 100000100)(/ (search-for-primes 10000000 10001000) (search-for-primes 1000000 1001000) 1.0)(/ (search-for-primes 100000000 100001000) (search-for-primes 10000000 10001000) 1.0)(/ (search-for-primes 1000000000 1000001000) (search-for-primes 100000000 100001000) 1.0)(/ (search-for-primes 10000000000 10000001000) (search-for-primes 1000000000 1000001000) 1.0)?
