anchor.diff:       (defvar ,name (make-instance ',name))))
   
   (defclass lexeme (parser-symbol) ())
  -
  -(defmethod print-object ((lexeme lexeme) stream)
  -  (print-unreadable-object (lexeme stream :type t :identity t)
  -    (format stream "~s ~s" (start-offset lexeme) (end-offset lexeme))))
   
   (defclass nonterminal (parser-symbol) ())
   
  
positive.code:    (preceding-parse-tree :initform nil :reader preceding-parse-tree)
     (parser-state :initform nil :initarg :parser-state :reader parser-state)))
  
  (defclass literal-object-mixin () ()
    (:documentation "Mixin for parser symbols representing
  literal (non-character) objects in the buffer."))
  
negative.code: 
  (defun get-drawing-options (highlighting-rules syntax parse-symbol)
    "Get the drawing options with which `parse-symbol' should be
  drawn. If `parse-symbol' or the stack-top of syntax, return NIL."
    (when (and parse-symbol (not (eq (stack-top syntax) parse-symbol)))
      (funcall highlighting-rules syntax parse-symbol)))
  
  (defstruct (pump-state
  