SICP习题 1.10(Ackermann函数)

(define (A x y)
(cond ((= y 0) 0)
((= x 0) (* 2 y))
((= y 1) 2)
(else (A (- x 1)
(A x (- y 1))))))

(A 1 10)

(A 2 4)

(A 3 3)

(define (f n)
(A 0 n))
(f 0)
(f 1)
(f 2)
(f 3)

没搞懂这题有什么意思