std::basic_format_context - cppreference.com (original) (raw)

Provides access to formatting state consisting of the formatting arguments and the output iterator.

1. The unspecified template argument is an output iterator that appends to 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.

2. The unspecified template argument is an output iterator that appends to std::wstring.

The behavior is undefined if OutputIt does not model std::output_iterator<const CharT&>.

A program that declares an explicit or partial specialization of std::basic_format_context is ill-formed, no diagnostic required.

std::basic_format_context objects can only be created by the implementation. User codes are only allowed to modify the format context via the format function of std::formatter specializations.

Contents

• 1 Member types
• 2 Member alias templates
• 3 Member functions
• 4 std::basic_format_context::arg
• 5 std::basic_format_context::locale
• 6 std::basic_format_context::out
• 7 std::basic_format_context::advance_to
  • 7.1 Example
  • 7.2 Defect reports

[edit] Member types

[edit] Member alias templates

[edit] Member functions

std::basic_format_context::arg

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::basic_format_context::locale

Returns the locale passed to the formatting function, or a default-constructed std::locale if the formatting function does not take a locale.

std::basic_format_context::out

Returns the iterator to the output buffer. The result is move-constructed from the stored iterator.

std::basic_format_context::advance_to

| 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.

[edit] Example

[edit] Defect reports

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