Реализовать алгоритм Маркова

(string-replace "abaabbab" "ab" "ba")

(defun ma (s)
  (if (zerop (strInd s "ab")) s (ma (strRep s "ab" "ba"))))
 
==> MA
 
(ma "abaabbab")
==> "bbbbaaaa"

(define (foo s old new)
  (let loop ((s s) (s2 (string-replace s old new)))
    (if (string-contains? s old)
        (loop s2 (string-replace s2 old new))
        s)))

(foo (foo "abaabbab" "ab" "ba") "a" "b")

(define (foo s . expression-patterns)
  (if (null? expression-patterns)
      s
      (let-values (((old new) (apply values (car expression-patterns))))
        (let loop ((s s) (s2 (string-replace s old new)))
          (if (string-contains? s old)
              (loop s2 (string-replace s2 old new))
              (apply foo s2 (rest expression-patterns)))))))
 
(foo "abaabbab" '("ab" "ba") '("a" "b") '("bb" "ab"))
;"abababab"