; string rotations
 
(define (take n xs)
  (let loop ((n n) (xs xs) (ys '()))
    (if (or (zero? n) (null? xs))
        (reverse ys)
        (loop (- n 1) (cdr xs)
              (cons (car xs) ys)))))
 
(define (rots xs)
  (let ((len (length xs)))
    (do ((xxs (append xs xs) (cdr xxs))
         (rots (list) (cons (take len xxs) rots))
         (n len (- n 1))) ((zero? n) rots))))
 
(define (string-rotations str)
  (map list->string (rots (string->list str))))
 
(display (string-rotations "Praxis")) (newline)
 

OyBzdHJpbmcgcm90YXRpb25zCgooZGVmaW5lICh0YWtlIG4geHMpCiAgKGxldCBsb29wICgobiBuKSAoeHMgeHMpICh5cyAnKCkpKQogICAgKGlmIChvciAoemVybz8gbikgKG51bGw/IHhzKSkKICAgICAgICAocmV2ZXJzZSB5cykKICAgICAgICAobG9vcCAoLSBuIDEpIChjZHIgeHMpCiAgICAgICAgICAgICAgKGNvbnMgKGNhciB4cykgeXMpKSkpKQoKKGRlZmluZSAocm90cyB4cykKICAobGV0ICgobGVuIChsZW5ndGggeHMpKSkKICAgIChkbyAoKHh4cyAoYXBwZW5kIHhzIHhzKSAoY2RyIHh4cykpCiAgICAgICAgIChyb3RzIChsaXN0KSAoY29ucyAodGFrZSBsZW4geHhzKSByb3RzKSkKICAgICAgICAgKG4gbGVuICgtIG4gMSkpKSAoKHplcm8/IG4pIHJvdHMpKSkpCgooZGVmaW5lIChzdHJpbmctcm90YXRpb25zIHN0cikKICAobWFwIGxpc3QtPnN0cmluZyAocm90cyAoc3RyaW5nLT5saXN0IHN0cikpKSkKCihkaXNwbGF5IChzdHJpbmctcm90YXRpb25zICJQcmF4aXMiKSkgKG5ld2xpbmUpCg==