gistfile1.clj

(defn ack [m n]
  (cond (zero? m) (inc n)
        (zero? n) (ack (dec m) 1)
        :else (ack (dec m) (ack m (dec n)))))

(defn ack-cps
  ([m n] (ack-cps m n identity))
  ([m n k]
     (loop [m m, n n, k k]
       (cond (zero? m) (k (inc n))
             (zero? n) (ack-cps (dec m) 1 k)
             :else (ack-cps m (dec n) #(ack-cps (dec m) % k))))))

(defn ack-stack [m n]
  (loop [m m, n n, stack ()]
    (cond (zero? m) (if (seq stack)
                      (recur (peek stack) (inc n) (pop stack))
                      (inc n))
          (zero? n) (recur (dec m) 1 stack)
          :else (recur m (dec n) (conj stack (dec m))))))