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