Petar Kapriš
a697f52405
To be noted: the drawing in exercise 1.14 is unfinished. I did it in a notebook, but haven't yet had the time to put it in a txt file.
54 lines
1.3 KiB
Scheme
54 lines
1.3 KiB
Scheme
#lang sicp
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(define (square x) (* x x))
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(define (expmod base exp m)
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(cond ((= exp 0) 1)
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((even? exp)
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(remainder (square (expmod base (/ exp 2) m))
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m))
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(else
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(remainder (* base (expmod base (- exp 1) m))
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m))))
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(define (smallest-divisor n)
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(find-divisor n 2))
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(define (find-divisor n test-divisor)
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(cond ((> (square test-divisor) n) n)
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((divides? test-divisor n) test-divisor)
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(else (find-divisor n (+ test-divisor 1)))))
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(define (divides? a b)
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(= (remainder b a) 0))
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(define (fermat-test n)
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(define (try-it a)
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(= (expmod a n n) a))
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(try-it (+ 1 (random (- n 1)))))
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(define (fast-prime? n times)
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(cond ((= times 0) true)
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((fermat-test n) (fast-prime? n (- times 1)))
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(else false)))
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(define (prime? n)
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(= n (smallest-divisor n)))
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(define (timed-prime-test n)
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(newline)
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(display n)
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(start-prime-test n (runtime)))
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(define (start-prime-test n start-time)
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(if (fast-prime? n 10)
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(report-prime (- (runtime) start-time))))
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(define (report-prime elapsed-time)
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(display " *** ")
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(display elapsed-time))
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(define (search-for-primes a b)
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(cond ((> a b) '())
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((not (even? a))
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(timed-prime-test a)
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(search-for-primes (+ a 2) b))
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(else (search-for-primes (+ a 1) b))))
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