Liaer

;gnu clisp 2.49

(defun factorial (a)
  (cond ((= a 0) 1)
        ((= a 1) 1)
        ((= a 2) 2)
        (t (* (factorial (- a 1)) a))
  )
)


(defun fib (n)
  (cond ((= n 0) 0)
        ((= n 1) 1)
        (t (+ (fib (- n 1)) (fib (- n 2))))
  )
)


(defun fact2 (n1 n2)
    (cond ((> n2 n1) nil)
        ((= n1 (- n2 1)) n2)
        ((= n1 n2) n2)
        ((= n1 (+ n2 1)) (+ n2 1))
        (t (* (fact2 (- n1 1) n2) n1))
    )
)

(defun acker (m n)
  (cond ((< n 0) nil)
        ((< m 0) nil)
        ((= m 0) (+ 1 n))
        ((= n 0) (acker (- m 1) 1))
        (t (acker (- m 1) (acker m (- n 1))))
  )
)

(print '----------------------------)
(print (fact2 1 1))
(print (fact2 -1 1))
(print (fact2 6 2))
(print (fact2 6 6))
(print '----------------------------)
(print (acker -1 5))
(print (acker 1 1))
(print (acker 0 4))
(print (acker 3 3))