29 lines
931 B
Scheme
29 lines
931 B
Scheme
(define (make-range start end)
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(cond ((= start end)
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`("," ,start))
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((= end (+ start 1))
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`("," ,start "," ,end))
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(else
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`("," ,start "-" ,end))))
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(define (range-extract-0 start end a)
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(cond ((null? a)
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(make-range start end))
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((= (+ 1 end) (car a))
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(range-extract-0 start (car a) (cdr a)))
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(else
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(append (make-range start end)
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(range-extract-0 (car a) (car a) (cdr a))))))
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(define (range-extract a)
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(apply string-append (map (lambda (x)
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(if (number? x)
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(number->string x)
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x))
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(cdr (range-extract-0 (car a) (car a) (cdr a))))))
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(range-extract '( 0 1 2 4 6 7 8 11 12 14
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15 16 17 18 19 20 21 22 23 24
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25 27 28 29 30 31 32 33 35 36
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37 38 39))
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