anchor.diff:  
   (defun avl-tree->output-line (width curx y next-gen)
      (if (< curx width)
  -       (cons (cdr (avl-retrieve next-gen (get-avl-key curx y width)))
  +       (string-append (if (avl-retrieve next-gen (get-avl-key curx y width)) "<td class=\"live\">&nbsp;</td>" "<td>&nbsp;</td>")
                (avl-tree->output-line width (1+ curx) y next-gen))
          nil))
   
   (defun avl-tree->output-lines (width height cury next-gen)
      (if (< cury height)
  -       (cons (coerce (avl-tree->output-line width 0 cury next-gen) 'string)
  +       (cons (string-append "<tr>" (string-append (avl-tree->output-line width 0 cury next-gen) "</tr>"))
                (avl-tree->output-lines width height (1+ cury) next-gen))
          nil))
   
   ;test input
  -(num-live-neighbors 0 4 4 1 1 
  +#|(num-live-neighbors 0 4 4 1 1 
                       (input-lines->avl-tree 0 0 4 (list (coerce "x xx" 'list)
                                                          (coerce "xxxx" 'list)
                                                          (coerce "x  x" 'list)
  
positive.code:                                                                                               (coerce "    " 'list))
                                                                                                (empty-tree))
                                                                 (empty-tree)))
  
  (defun main (state)
  	(string-list->stdout (avl-tree->output-lines 4 4 0 (build-next-generation 4 4 0 (input-lines->avl-tree 0 0 4 (list (coerce " x  " 'list)
  		                                                                                          (coerce "xx  " 'list)
  		                                                                                          (coerce "    " 'list)
  		                                                                                          (coerce "    " 'list))
  		                                                                                          (empty-tree))
  		                                                           (empty-tree))) state))
negative.code: (defun build-next-generation-cell (width height x y last-gen next-gen)
     (let* ((n (num-live-neighbors 0 width height x y last-gen))
            (result (if (null (avl-retrieve last-gen (get-avl-key x y width)))
                        (if (= n 3) "x" nil)
                        (if (or (< n 2) (> n 3)) nil "x"))))
           (if result
               (avl-insert next-gen (get-avl-key x y width) result)
               next-gen)))
                  
  ; added curx counter
  (defun build-next-generation-row (width height curx y last-gen next-gen)
  