1.10.scm

(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) ; 1024
(A 2 2)  ; 4
(A 3 3)  ; 65536

(define (f n) (A 0 n)) ; 2n
(define (g n) (A 1 n)) ; n=0: 0, n>0: 2^n
(define (h n) (A 2 n)) ; n=0: 0; n=1: 2; n>1: 2^2^...(n-1) times