protected function insertValues( $args )
	{
		$variables = $this->getVariables();
		if( count( $args ) < count( $variables ) )
			trigger_error( "to less arguments, more variables used", E_USER_WARNING );
		$exp = str_replace( $variables, $args, $this->getExpression() );
		$eval_code = "return (".$exp.");";
		return $eval_code;
	}