11 lines
240 B
Racket
11 lines
240 B
Racket
#lang racket
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(require math)
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(define (digits n)
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(map (compose1 string->number string)
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(string->list (number->string n))))
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(define (cast-out-nines n)
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(with-modulus 9
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(for/fold ([sum 0]) ([d (digits n)])
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(mod+ sum d))))
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