std::basic_format_args

 

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Utilities library

Language support Type support (basic types, RTTI, type traits) Library feature-test macros (C++20) Dynamic memory management Program utilities Error handling Coroutine support (C++20) Variadic functions launder (C++17) initializer_list (C++11) source_location (C++20) Three-way comparison (C++20) three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20) is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) integer_sequence (C++14) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_not_equalcmp_lesscmp_greatercmp_less_thancmp_greater_than (C++20)(C++20)(C++20)(C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) forward (C++11) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) apply (C++17) make_from_tuple (C++17) optional (C++17) any (C++17) variant (C++17) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

Formatting library

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)

Formatter

formatter (C++20)

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)

Formatting arguments

basic_format_arg (C++20)

basic_format_argsformat_argswformat_argsformat_args_t (C++20)(C++20)(C++20)(C++20)

visit_format_arg (C++20)

make_format_argsmake_wformat_args (C++20)(C++20)

Format error

format_error (C++20)

 

Defined in header <format>
template<class Context> class basic_format_args;	(1)	(since C++20)
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)
template<class OutputIt, class CharT> using format_args_t = basic_format_args<std::basic_format_context<OutputIt, CharT>>;	(4)	(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) noexcept;	(2)

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).

See also

basic_format_arg (C++20)

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