19 lines
811 B
Scheme
19 lines
811 B
Scheme
(define (first-digit n) (string->number (string (string-ref (number->string n) 0))))
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(define (last-digit n) (modulo n 10))
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(define (bookend-number n) (+ (* 10 (first-digit n)) (last-digit n)))
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(define (gapful? n) (and (>= n 100) (zero? (modulo n (bookend-number n)))))
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(define (gapfuls-in-range start size)
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(let ((found 0) (result '()))
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(do ((n start (+ n 1))) ((>= found size) (reverse result))
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(if (gapful? n)
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(begin (set! result (cons n result)) (set! found (+ found 1)))))))
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(define (report-range range)
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(apply (lambda (start size)
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(newline)
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(display "The first ")(display size)(display " gapful numbers >= ")
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(display start)(display ":")(newline)
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(display (gapfuls-in-range start size))(newline)) range))
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(map report-range '((100 30) (1000000 15) (1000000000 10)))
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