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  1. ; reverse string ignoring special characters
  2.  
  3. (define (string-reverse! str)
  4.   (let loop ((lo 0) (hi (- (string-length str) 1)))
  5.     (cond ((<= hi lo) str)
  6.           (else (let ((t (string-ref str lo)))
  7.                   (string-set! str lo (string-ref str hi))
  8.                   (string-set! str hi t)
  9.                   (loop (+ lo 1) (- hi 1)))))))
  10.  
  11. (display (string-reverse! "a!b3c")) (newline)
  12.  
  13. (define (string-reverse! str)
  14.   (let loop ((lo 0) (hi (- (string-length str) 1)))
  15.     (cond ((<= hi lo) str)
  16.           ((not (char-alphabetic? (string-ref str lo)))
  17.             (loop (+ lo 1) hi))
  18.           ((not (char-alphabetic? (string-ref str hi)))
  19.             (loop lo (- hi 1)))
  20.           (else (let ((t (string-ref str lo)))
  21.                   (string-set! str lo (string-ref str hi))
  22.                   (string-set! str hi t)
  23.                   (loop (+ lo 1) (- hi 1)))))))
  24.  
  25. (display (string-reverse! "a!b3c")) (newline)
Success #stdin #stdout 0s 7264KB
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Standard input is empty
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c3b!a
c!b3a
https://ideone.com/Szld2K
language:
Scheme (chicken 4.13)
created:
8 years ago
visibility:
secret

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