NAME¶

std::formattable - std::formattable

Synopsis¶

Defined in header <format>
template< class T, class CharT >

concept formattable = /* formattable_with */<
std::remove_reference_t<T>, (1) (since C++23)
std::basic_format_context</* fmt_iter_for */<CharT>, CharT>

>;
Helper templates
template< class CharT > (2) (exposition only*)
using /* fmt_iter_for */ = /* unspecified */;
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, (3) (exposition only*)
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>;

};

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 provided
std::basic_format_context was not provided

See also¶

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