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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 twentyone)
#:export (sm-divisor-of-199
sm-divisor-of-1999
sm-divisor-of-19999))
(define (small-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 (square x)
(expt x 2))
(define (sm-divisor-of-199)
(small-divisor 199))
(define (sm-divisor-of-1999)
(small-divisor 1999))
(define (sm-divisor-of-19999)
(small-divisor 19999))
;;;
;;; scheme@(guile-user)> ,use (net ricketyspace sicp one twentyone)
;;; ...
;;; scheme@(guile-user)> (sm-divisor-of-199)
;;; $3 = 199
;;; scheme@(guile-user)> (sm-divisor-of-1999)
;;; $4 = 1999
;;; scheme@(guile-user)> (sm-divisor-of-19999)
;;; $5 = 7
;;;
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