(defun directive-to-list (directive &optional (cursor '(0 0)))
  (multiple-value-bind (direction count)
      (3convert directive)
    (let (place increment coords)
      (case direction
	(#\U (setf place (second cursor) increment 1))
	(#\D (setf place (second cursor) increment -1))
	(#\R (setf place (first cursor) increment 1))
	(#\L (setf place (first cursor) increment -1)))
      (dotimes (i count)
	(incf place increment)
	(push cursor coords))
      (values coords cursor))))