Function: GEN-MEMO

Source

(defun gen-memo (fn key test)
  (let ((table (make-hash-table :test test)))
    (values table
	    (lambda (&rest args)
	      (let ((k (funcall key args)))
		(multiple-value-bind (val found-p) (gethash k table)
		  (if found-p
		      val
		      (setf (gethash k table)
			    (apply fn args)))))))))