anchor.diff:  
   
   (defun tree-to-ascii (tlee &key boxed format-fun background
  -                      to-length from-length)
  +                      to-length from-length base)
     "
   tlee:        is a list-based tree, whose car is a \"node\",
                and whose cdr is the list of children.
  
positive.code:             (max (tree-to-ascii-box-height node-box)
                   (tree-to-ascii-box-height children-box)))
        (setf (tree-to-ascii-box-base node-box)
              (tree-to-ascii-box-base children-box))
        ) ;;when
      (setf (tree-to-ascii-box tree) node-box)
      node-box))
  
  
negative.code:                                            :boxed boxed
                                             :format-fun format-fun
                                             :to-length  to-length
                                             :from-length from-length
                                             :base base))
           (pict (make-instance 'picture
                   :width (tree-to-ascii-box-width box) 
                   :height (tree-to-ascii-box-height box)
  