NAME¶

std::basic_format_args - std::basic_format_args

Synopsis¶

Defined in header <format>
template< class Context > (1) (since C++20)
class basic_format_args;
using format_args = basic_format_args<std::format_context>; (2) (since C++20)
using wformat_args = basic_format_args<std::wformat_context>; (3) (since C++20)

Provides access to formatting arguments.

Member functions¶

constructor constructs a basic_format_args object
(public member function)
get returns formatting argument at the given index
(public member function)

std::basic_format_args::basic_format_args

basic_format_args() noexcept; (1)
template< class... Args >
basic_format_args( const /*format-arg-store*/<Context, Args...>& store ) (2)
noexcept;

1) Constructs a basic_format_args object that does not hold any formatting argument.
2) Constructs a basic_format_args object from the result of a call to
std::make_format_args or std::make_wformat_args.

std::basic_format_args has reference semantics. It is the programmer's
responsibility to ensure that *this does not outlive store (which, in turn, should
not outlive the arguments to std::make_format_args or std::make_wformat_args).

std::basic_format_args::get

std::basic_format_arg<Context> get( std::size_t i ) const noexcept;

Returns a std::basic_format_arg holding the i-th argument in args, where args is the
parameter pack passed to std::make_format_args or std::make_wformat_args.

If there's no such formatting argument (i.e. *this was default-constructed or i is
not less than the number of formatting arguments), returns a default-constructed
std::basic_format_arg (holding a std::monostate object).

Deduction guides

template< class Context, class... Args >
basic_format_args( /*format-arg-store*/<Context, Args...> ) -> (since C++20)
basic_format_args<Context>;

Example¶

This section is incomplete
Reason: no example

Defect reports

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

DR Applied to Behavior as published Correct behavior
P2216R3 C++20 format_args_t was provided due to removed
overparameterization of vformat_to
LWG3810 C++20 basic_format_args has no deduction guide added

See also¶

basic_format_arg class template that provides access to a formatting argument for
(C++20) user-defined formatters
(class template)

Category:¶

* Todo no example