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Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 7387c8f97b
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Task/Digital-root/Racket/digital-root.rkt Normal file
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#lang racket
(define/contract (additive-persistence/digital-root n (ap 0))
(->* (natural-number/c) (natural-number/c) (values natural-number/c natural-number/c))
(define/contract (sum-digits x (acc 0))
(->* (natural-number/c) (natural-number/c) natural-number/c)
(if (= x 0)
acc
(let-values (((q r) (quotient/remainder x 10)))
(sum-digits q (+ acc r)))))
(if (< n 10)
(values ap n)
(additive-persistence/digital-root (sum-digits n) (+ ap 1))))
(module+ test
(require rackunit)
(for ((n (in-list '(627615 39390 588225 393900588225)))
(ap (in-list '(2 2 2 2)))
(dr (in-list '(9 6 3 9))))
(call-with-values
(lambda () (additive-persistence/digital-root n))
(lambda (a d)
(check-equal? a ap)
(check-equal? d dr)
(printf ":~a has additive persistence ~a and digital root of ~a;~%" n a d)))))