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;;;; Under Creative Commons Attribution-ShareAlike 4.0
;;;; International. See
;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
(define-module (net ricketyspace sicp one twentythree)
#:use-module (net ricketyspace sicp utils)
#:export (smallest-divisor))
(define (square x)
(expt x 2))
(define (divides? a b)
(= (remainder b a) 0))
(define (next n)
(cond ((= n 2) 3)
(else (+ 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))
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