code: public function localeFormat($decPoint = null, $separator = null)
      {
          if (!isset($decPoint) || !isset($separator)) {
              $locale = localeconv();
  
              if (!isset($decPoint))
                  $decPoint = $locale["decimal_point"];
  
              if (!isset($separator))
                  $separator = $locale["thousands_sep"];
          }
  
          return $this->format($decPoint, $separator);
      }
docs: This is the same of format(), only that it will fallback to machine locale values
  when some argument is missing.
  
  @param string|null $decPoint
  @param string|null $separator
  @return string