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std::formattable - cppreference.com

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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 concept formattable specifies that std::formatter<std::remove_cvref_t<T>, CharT> meets the requirements of BasicFormatter and Formatter (if std::remove_reference_t<T> is const-qualified).

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

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 3925 C++23 the second template argument of std::basic_format_context was not provided provided

See also

defines formatting rules for a given type
(class template) [edit]
abstracts formatting operations for a given formatting argument type and character type
(named requirement)
defines functions used by the formatting library
(named requirement)