SICP exercise 1.10 in Clojure

exercise-1.10.clj

; compute the Ackermann's function
(defn A [x y]
  (cond (= y 0) 0
        (= x 0) (*' 2 y)
        (= y 1) 2
        :else (A (- x 1)
                 (A x (- y 1)))))

; f(x) = 2x
(defn f [n]
  (A 0 n))

; g(n) = 2^n
(defn g [n]
  (A 1 n))

; h(n) = ?
(defn h [n]
  (A 2 n))

; (A 2 n)
; (A 1 (A 2 (- n 1)))

; k(n) = 5n^2
(defn k [n]
  (* 5 n n))