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