メタマジック・ゲームからハノイの塔写経

(define carry-one-disk
  (lambda (sn dn)
    (string-append sn dn)))

(define move-tower
  (lambda (n sn dn hn)
    (cond ((= n 1) (carry-one-disk sn dn))
          (else (list (move-tower (sub1 n) sn hn dn)
                      (carry-one-disk sn dn)
                      (move-tower (sub1 n) hn dn sn))))))


(define carry-one-disk-flatten
  (lambda (sn dn)
    (list (string-append sn dn))))

(define move-tower-flatten
  (lambda (n sn dn hn)
    (cond ((= n 1) (carry-one-disk-flatten sn dn))
          (else (append (move-tower-flatten (sub1 n) sn hn dn)
                      (carry-one-disk-flatten sn dn)
                      (move-tower-flatten (sub1 n) hn dn sn))))))