std::formattable

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(C++26)

Standard format specification
Formatting functions
format (C++20)
format_to (C++20)
format_to_n (C++20)
formatted_size (C++20)
vformat (C++20)
vformat_to (C++20)
Format strings
basic_format_stringformat_stringwformat_string (C++20)(C++20)(C++20)
runtime_format (C++26)
Formatting concepts
formattable (C++23)
Formatter
formatter (C++20)
formatter<pair-or-tuple> (C++23)
formatter<range> (C++23)
range_formatter (C++23)
enable_nonlocking_formatter_optimization (C++23)
basic_format_parse_contextformat_parse_contextwformat_parse_context (C++20)(C++20)(C++20)
basic_format_contextformat_contextwformat_context (C++20)(C++20)(C++20)
range_format (C++23)
format_kind (C++23)
Formatting arguments
basic_format_arg (C++20)
basic_format_arg::handle (C++20)
basic_format_argsformat_argswformat_args (C++20)(C++20)(C++20)
visit_format_arg (C++20)(deprecated in C++26)
make_format_argsmake_wformat_args (C++20)(C++20)
Format error
format_error (C++20)

Defined in header`<format>`
template<class T,class CharT> concept formattable=/* formattable_with /< std::remove_reference_t<T>, std::basic_format_context</ fmt_iter_for */<CharT>, CharT> >;	(1)	(since C++23)
Helper templates
template<class CharT> using/* fmt_iter_for /=/ unspecified */;	(2)	(exposition only*)
template<class T,class Context, class Formatter= typename Context::template formatter_type<std::remove_const_t<T>>> concept/* formattable_with */= std::semiregular<Formatter>&& requires(Formatter& f,const Formatter& cf, T&& t, Context fc, std::basic_format_parse_context< typename Context::char_type > pc){ { f.parse(pc)}->std::same_as<typename decltype(pc)::iterator>; { cf.format(t, fc)}->std::same_as<typename Context::iterator>; };	(3)	(exposition only*)

The conceptformattable specifies thatstd::formatter<std::remove_cvref_t<T>, CharT> meets the requirements ofBasicFormatter andFormatter (ifstd::remove_reference_t<T> is const-qualified).

The exposition-only alias template/* fmt_iter_for */ yields an unspecified type that satisfiesstd::output_iterator<const CharT&>.

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3925	C++23	the second template argument ofstd::basic_format_context was not provided	provided

formatter (C++20)	defines formatting rules for a given type (class template)[edit]
BasicFormatter (C++20)	abstracts formatting operations for a given formatting argument type and character type (named requirement)
Formatter (C++20)	defines functions used by theformatting library (named requirement)

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