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  1. ; double space
  2.  
  3. (define (double-space oldstr)
  4.   (define (space? str idx)
  5.     (char=? (string-ref str idx) #\space))
  6.   (let ((oldlen (string-length oldstr)))
  7.     (do ((oldidx 0 (+ oldidx 1))
  8.          (count 0 (+ count (if (space? oldstr oldidx) 1 0))))
  9.         ((= oldidx oldlen)
  10.           (let* ((newlen (+ oldlen count))
  11.                  (newstr (make-string newlen #\space)))
  12.             (do ((oldidx 0 (+ oldidx 1))
  13.                  (newidx 0 (+ newidx (if (space? newstr newidx) 2 1))))
  14.                 ((= oldidx oldlen) newstr)
  15.               (string-set! newstr newidx (string-ref oldstr oldidx))))))))
  16.  
  17. (display (double-space "hello")) (newline)
  18. (display (double-space "hello hello")) (newline)
  19. (display (double-space "hello  hello")) (newline)
  20. (display (double-space "hello   hello")) (newline)
  21. (display (double-space "hello hello hello")) (newline)
  22. (display (double-space " hello ")) (newline)
  23. (display (double-space "")) (newline)
  24. (display (double-space " ")) (newline)
  25. (display (double-space "  ")) (newline)
  26. (display (double-space "   ")) (newline) (newline)
  27.  
  28. (define (double-space str)
  29.   (let loop ((xs (string->list str)) (zs (list)))
  30.     (if (null? xs) (list->string (reverse zs))
  31.       (if (char=? (car xs) #\space)
  32.           (loop (cdr xs) (cons #\space (cons #\space zs)))
  33.           (loop (cdr xs) (cons (car xs) zs))))))
  34.  
  35. (display (double-space "hello")) (newline)
  36. (display (double-space "hello hello")) (newline)
  37. (display (double-space "hello  hello")) (newline)
  38. (display (double-space "hello   hello")) (newline)
  39. (display (double-space "hello hello hello")) (newline)
  40. (display (double-space " hello ")) (newline)
  41. (display (double-space "")) (newline)
  42. (display (double-space " ")) (newline)
  43. (display (double-space "  ")) (newline)
  44. (display (double-space "   ")) (newline)
Success #stdin #stdout 0.01s 42848KB
comments (?)
stdin
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Standard input is empty
stdout
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hello
hello  hello
hello    hello
hello      hello
hello  hello  hello
  hello  

  
    
      

hello
hello  hello
hello    hello
hello      hello
hello  hello  hello
  hello
https://ideone.com/YoEiw9
language:
Scheme (guile 2.2.4)
created:
7 years ago
visibility:
public

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