anchor.diff:                                 :equal-fn (read-equal-fn container)
                                  :hash-fn (read-hash-fn container)
                                  :root result
  -                               :equal-fn (read-equal-fn container)
                                  :max-depth (read-max-depth container))
                   rep
                   old)))))
  
positive.code:                                    :equal-fn (read-equal-fn container)
                                     :hash-fn (read-hash-fn container)
                                     :root result
                                     :equal-fn (read-equal-fn container)
                                     :max-depth (read-max-depth container)
                                     :size (1+ (access-size container)))
                      container)
  
negative.code:                                        (setf prev-node node
                                               prev-index index))))))
          (setf (access-root container) result)
          (incf (access-size container))
          container))))
  
  
  