anchor.diff:              (integerp width)
               (tree? last-gen)                 
               (consp input-lines))
  -       (if (null (car input-lines))
  +       (if (endp (car input-lines))
              (input-lines->avl-tree 0 (1+ y) width (cdr input-lines) last-gen)
              (input-lines->avl-tree (1+ x) y width (cons (cdar input-lines) (cdr input-lines))
                                     (if (equal (car (car input-lines)) #\x)
  
positive.code:       (let ((avl-tree (car things))
              (width (cadr things))
              (height (caddr things)))
             (string-list->stdout (avl-tree->output-lines width height 0 (build-next-generation width height 0 avl-tree
  		                                                           (empty-tree))) state))))
negative.code:        last-gen))
  
  (defun strings->char-lists (lst)
     (if (endp lst)
         nil
         (cons (coerce (car lst) 'list) (strings->char-lists (cdr lst)))))
  
  