(defmacro defun-mem (name params &body body)
	(let ((*name-vals* (gensym))
	      (value       (gensym))
	      (exist       (gensym)))
		`(progn
		 	(defvar ,*name-vals* (make-hash-table))
			(defun ,name ,params
				(multiple-value-bind
					(,value ,exist)
					(gethash (list ,@params) ,*name-vals*)
					(if ,exist
						,value
						(setf
							(gethash (list ,@params) ,*name-vals*)
							(progn ,@body))))))))
(format t "~a~%" (macroexpand-1
	'(defun-mem ack-mem (m n)
		(if (= m 0)
			(+ n 1)
			(if (= n 0)
				(ack-mem (- m 1) 1)
				(ack-mem (- m 1) (ack-mem m (- n 1))))))))