Defined in header <format> | ||
|---|---|---|
template< class OutputIt, class CharT > class basic_format_context; | (1) | (since C++20) |
using format_context = basic_format_context</* unspecified */, char>; | (2) | (since C++20) |
using wformat_context = basic_format_context</* unspecified */, wchar_t>; | (3) | (since C++20) |
Provides access to formatting state consisting of the formatting arguments and the output iterator.
The behavior is undefined if OutputIt does not model std::output_iterator<const CharT&>.
std::string, such as std::back_insert_iterator<std::string>. Implementations typically use an iterator to type-erased buffer type that supports appending to any contiguous and resizable container.std::wstring.| Type | Definition |
|---|---|
iterator | OutputIt |
char_type | CharT |
| Type | Definition |
|---|---|
formatter_type<T> | std::formatter<T, CharT> |
| arg | returns the argument at the given index (public member function) |
| locale | returns the locale used for locale-specific formatting (public member function) |
| out | returns the iterator to output buffer (public member function) |
| advance_to | advances the output iterator to the given position (public member function) |
std::basic_format_arg<basic_format_context> arg( std::size_t id ) const; |
Returns a std::basic_format_arg holding the id-th argument in args, where args is the parameter pack or std::basic_format_args object passed to the formatting function.
If id is not less than the number of formatting arguments, returns a default-constructed std::basic_format_arg (holding a std::monostate object).
std::locale locale(); |
Returns the locale passed to the formatting function, or a default-constructed std::locale if the formatting function does not take a locale.
iterator out(); |
Returns the iterator to the output buffer. The result is move-constructed from the stored iterator.
void advance_to( iterator it ); |
Move assigns it to the stored output iterator. After a call to advance_to, the next call to out() will return an iterator with the value that it had before the assignment.
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3567 | C++20 | basic_format_context does not work move-only iterator types | made to move iterators |
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