function name( $i ){
		if( is_int($i) ){
			if( ! isset($this->names[$i]) ){
				trigger_error("symbol ".var_export($i,1)." is unknown in ".get_class($this), E_USER_NOTICE );
				return 'UNKNOWN';
			}
			else {
				return $this->names[$i];
			}
		}
		else if ( ! isset($this->literals[$i]) ){
			trigger_error("literal symbol ".var_export($i,1)." is unknown in ".get_class($this), E_USER_NOTICE );
		}
		return $i;
	}