anchor.diff:                               (if (typep node 'spatial-tree-leaf-node)
                                    'spatial-tree-leaf-node
                                    'x-tree-node)))
  +             (unless (typep node 'spatial-tree-leaf-node)
  +               (let ((split-tree (split-tree node)))
  +                 (setf (split-tree node) (split-tree-from-set one split-tree)
  +                       (split-tree new-node) (split-tree-from-set two split-tree))))
                new-node)
               ((and (not (typep node 'spatial-tree-leaf-node))
                     (let ((split-tree (split-tree node)))
  
positive.code:   ())
  
  (defvar *split*)
  
  (defun find-cons-with-leaf (object conses)
    (cond
      ((atom conses) nil)
  
negative.code:                     (make-instance 'x-tree-node
                                     :children (list (root-node tree) new))))
                 (setf (parent (root-node tree)) new-root
                       (split-tree new-root) (cons (root-node tree) new)
                       (root-node tree) new-root
                       (parent new) new-root)))))))
      tree))
  