anchor.diff:                                      ((nil) (push (route-booking lostmark subrroute subnode) basebook)))))))
                      (push (route-booking lostmark rroute node) basebook))))
                (stack-ref-booking (cited node cont cur)
  -               (and cur (push (route-booking citedmark cur node nil cited) basebook))
  +               (push (route-booking citedmark cur node nil cited) basebook)
                  (car (push (route-booking refmark cited node cont) modbook))))
         (symbol-macrolet ((cont (lambda () (if (proper-list-p mnode)
                                              next-level
  
positive.code: 
  (defun rdiff% (base modified refmark lostmark citedmark allowed-distance)
    (let (basebook modbook)
      (labels ((booking-as-ref (cited node cont &optional cur)
                 (multiple-value-bind (booking relation mark)
                   (check-booking cited basebook)
                   (if booking
  
negative.code:         (traverse/route ((bnode base) (mnode modified)) (rroute invalid-p)
            (cond ((and (not (invalid-p mnode)) (not (invalid-p bnode)))
                   (acond ((equal mnode bnode)
                           (booking-as-ref rroute bnode cont rroute))
                          ((find-ref-candidates mnode rroute allowed-distance base)
                           (booking-as-lost rroute bnode)
                           (booking-as-ref it mnode cont rroute))
  