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  1. ; rotated palindrome
  2.  
  3. (define (split n xs)
  4.   (let loop ((n n) (xs xs) (zs '()))
  5.     (if (or (zero? n) (null? xs))
  6.         (values (reverse zs) xs)
  7.         (loop (- n 1) (cdr xs) (cons (car xs) zs)))))
  8.  
  9. (define (string-reverse str)
  10.   (list->string (reverse (string->list str))))
  11.  
  12. (define (string-rotate n str)
  13.   (call-with-values
  14.     (lambda () (split n (string->list str)))
  15.     (lambda (front back) (list->string (append back front)))))
  16.  
  17. (define (rot-pal? str)
  18.   (let loop ((n (string-length str)) (str str))
  19.     (if (zero? n) #f
  20.       (if (string=? str (string-reverse str)) #t
  21.         (loop (- n 1) (string-rotate 1 str))))))
  22.  
  23. (display (rot-pal? "abcdedcba")) (newline)
  24. (display (rot-pal? "dedcbaabc")) (newline)
  25. (display (rot-pal? "abcdefghi")) (newline)
Success #stdin #stdout 0.04s 8280KB
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#t
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https://ideone.com/DqWBKA
language:
Scheme (guile 2.2.4)
created:
6 years ago
visibility:
public

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