protected static function mustBeFloat($arg, $arg_name = null)
    {
        if(!is_float($arg) && !($arg instanceof N)){
            throw new \InvalidArgumentException(
                sprintf(
                    '%s must be a primitive float PHP type or '
                    .'object \Malenki\Bah\N',
                    is_null($arg_name) ? 'Argument' : $arg_name
                )
            );
        }
    }