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  1. ; distinct characters
  2.  
  3. (define (distinct? str)
  4.   (call-with-current-continuation
  5.     (lambda (return)
  6.       (let ((cs (string->list str)))
  7.         (do ((cs cs (cdr cs))) ((null? cs) #t)
  8.           (do ((ds (cdr cs) (cdr ds))) ((null? ds))
  9.             (when (char=? (car cs) (car ds))
  10.               (return #f))))))))
  11.  
  12. (display (distinct? "Programming")) (display " ")
  13. (display (distinct? "Praxis")) (newline)
  14.  
  15. (define (distinct? str)
  16.   (let loop ((cs (sort (string->list str) char<?)))
  17.     (if (null? (cdr cs)) #t
  18.       (if (char=? (car cs) (cadr cs)) #f
  19.         (loop (cdr cs))))))
  20.  
  21. (display (distinct? "Programming")) (display " ")
  22. (display (distinct? "Praxis")) (newline)
  23.  
  24. (define (distinct? str)
  25.   (let ((letters (make-hash-table)))
  26.     (let loop ((cs (string->list str)))
  27.       (if (null? cs) #t
  28.         (if (hash-ref letters (car cs) #f) #f
  29.           (begin (hash-set! letters (car cs) 1)
  30.                  (loop (cdr cs))))))))
  31.  
  32. (display (distinct? "Programming")) (display " ")
  33. (display (distinct? "Praxis")) (newline)
Success #stdin #stdout 0.01s 42848KB
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Standard input is empty
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#f #t
#f #t
#f #t
https://ideone.com/0Yw1Bd
language:
Scheme (guile 2.2.4)
created:
6 years ago
visibility:
public

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