(defmacro defmemofun (name (. args) . body)
  (let ((hash (gensym "hash-"))
        (argl (gensym "args-"))
        (hent (gensym "hent-"))
        (uniq (copy-str "uniq")))
    ^(let ((,hash (hash :equal-based)))
       (defun ,name (,*args)
         (let* ((,argl (list ,*args))
                (,hent (inhash ,hash ,argl ,uniq)))
           (if (eq (cdr ,hent) ,uniq)
             (set (cdr ,hent) (block ,name (progn ,*body)))
             (cdr ,hent)))))))

(defmemofun ack (m n)
  (cond
    ((= m 0) (+ n 1))
    ((= n 0) (ack (- m 1) 1))
    (t (ack (- m 1) (ack m (- n 1))))))

(each ((i (range 0 3)))
  (each ((j (range 0 4)))
    (format t "ack(~a, ~a) = ~a\n" i j (ack i j))))