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  1. ; reversing digits
  2.  
  3. (define (digits n . args)
  4.   (let ((b (if (null? args) 10 (car args))))
  5.     (let loop ((n n) (d '()))
  6.       (if (zero? n) d
  7.           (loop (quotient n b)
  8.                 (cons (modulo n b) d))))))
  9.  
  10. (define (undigits ds . args)
  11.   (let ((b (if (null? args) 10 (car args))))
  12.     (let loop ((ds ds) (n 0))
  13.       (if (null? ds) n
  14.           (loop (cdr ds) (+ (* n b) (car ds)))))))
  15.  
  16. (define (timing rev)
  17.   (time
  18.     (let ((count 0))
  19.       (do ((n 1 (+ n 1)))
  20.           ((< 50000 n) count)
  21.         (when (= n (rev n))
  22.           (set! count (+ count 1)))))))
  23.  
  24. (define (rev1 n) ; iterative 1731
  25.   (let loop ((n n) (z 0))
  26.     (if (zero? n) z
  27.       (loop (quotient n 10)
  28.             (+ (* z 10) (modulo n 10))))))
  29.  
  30. (define (rev2 n) ; recursive 1747
  31.   (define (rev n r)
  32.     (if (zero? n) r
  33.       (rev (quotient n 10)
  34.            (+ (* r 10) (modulo n 10)))))
  35.   (rev n 0))
  36.  
  37. (define (rev3 n) ; numeric split 2918
  38.   (undigits (reverse (digits n))))
  39.  
  40. (define (rev4 n) ; string split 2527
  41.   (string->number
  42.     (list->string
  43.       (reverse
  44.         (string->list
  45.           (number->string n))))))
  46.  
  47. (display (timing rev1)) (newline)
  48. (display (timing rev2)) (newline)
  49. (display (timing rev3)) (newline)
  50. (display (timing rev4)) (newline)
Success #stdin #stdout #stderr 2.7s 7380KB
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Standard input is empty
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598
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stderr
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0.669s CPU time, 0.103s GC time (major), 300016 mutations, 63/5602 GCs (major/minor)
0.672s CPU time, 0.1s GC time (major), 300016 mutations, 60/5534 GCs (major/minor)
1.209s CPU time, 0.17s GC time (major), 600016 mutations, 143/10053 GCs (major/minor)
0.138s CPU time, 0.005s GC time (major), 16 mutations, 3/1193 GCs (major/minor)
https://ideone.com/vzwkwD
language:
Scheme (chicken 4.13)
created:
8 years ago
visibility:
public

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