std::range_formatter(3)

NAME
std::range_formatter - std::range_formatter

Synopsis
   Defined in header <format>
   template< class T, class CharT = char >
       requires std::same_as<std::remove_cvref_t<T>, T> && (since C++23)
   std::formattable<T, CharT>
   class range_formatter;
   The std::range_formatter is a helper class template for implementing std::formatter
   specializations for range types.

Member objects
   Member name Definition
   underlying_ (private) the underlying formatter of type std::formatter<T, CharT>
                        (exposition-only member object*)
                        a string representing the separator of the range
   separator_ (private) formatted result. The default separator is ", ".
                        (exposition-only member object*)
                        a string representing the opening bracket of the range
   opening-bracket_ (private) formatted result. The default opening bracket is "[".
                        (exposition-only member object*)
                        a string representing the closing bracket of the range
   closing-bracket_ (private) formatted result. The default closing bracket is "]".
                        (exposition-only member object*)

Member functions
   set_separator sets a specified separator for the range formatted result
                 (public member function)
                 sets a specified opening and closing brackets for the range formatted
   set_brackets result
                 (public member function)
   underlying returns the underlying formatter
                 (public member function)
   parse parses the format specifier as specified by range-format-spec
                 (public member function)
   format writes the range formatted output as specified by range-format-spec
                 (public member function) std::range_formatter::set_separator
   constexpr void set_separator( std::basic_string_view<CharT> sep ) noexcept;
   Assigns sep to separator_. std::range_formatter::set_brackets
   constexpr void set_brackets( std::basic_string_view<CharT> opening,
                        std::basic_string_view<CharT> closing ) noexcept;
   Assigns opening and closing to opening-bracket_ and closing-bracket_, respectively. std::range_formatter::underlying
   constexpr std::formatter<T, CharT>& underlying(); (1)
   constexpr const std::formatter<T, CharT>& underlying() const; (2)
   Returns underlying_ (the underlying formatter). std::range_formatter::parse
   template< class ParseContext >
   constexpr auto parse( ParseContext& ctx ) -> ParseContext::iterator;
   Parses the format specifiers as a range-format-spec and stores the parsed specifiers
   in the current object.
   Calls underlying_.parse(ctx) to parse format-spec in range-format-spec or, if the
   latter is not present, an empty format-spec.
   If range-type or the n option is present, the values of opening-bracket_,
   closing-bracket_, and separator_ are modified as required.
   It calls underlying_.set_debug_format() if:
     * the range-type is neither s nor ?s,
     * underlying_.set_debug_format() is a valid expression, and
     * there is no range-underlying-spec.
   Returns an iterator past the end of the range-format-spec. std::range_formatter::format
   template< ranges::input_range R, class FormatContext >
     requires std::formattable<ranges::range_reference_t<R>, CharT> &&
              std::same_as<std::remove_cvref_t<ranges::range_reference_t<R>>, T>
   auto format( R&& r, FormatContext& ctx ) const -> FormatContext::iterator;
   If the range-type was either s or ?s, it writes the formatted
   std::basic_string<CharT>(std::from_range, r) as a string or an escaped string,
   respectively, into ctx.out().
   Otherwise, it writes the following into ctx.out() as specified by range-format-spec,
   in order:
     * opening-bracket_,
     * for each formattable element e of the range r:
     * the result of writing e via underlying_, and
     * separator_, unless e is the last element of r, and
     * closing-bracket_.
   Returns an iterator past the end of the output range.
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
   LWG 3892 C++23 the formatting of nested ranges was incorrect corrected

See also
   formatter defines formatting rules for a given type
   (C++20) (class template)