std::basic_format_context - cppreference.com
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    std::basic_format_context

    From cppreference.com
     
    C++
     
    Text processing library
     
    Formatting library
    Standard format specification
    Formatting functions
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    Format strings
    (C++20)(C++20)(C++20)
    (C++26)
    Formatting concepts
    (C++23)
    Formatter
    (C++20)
    (C++23)
    (C++23)
    (C++23)
    (C++23)
    (C++20)(C++20)(C++20)
    (C++20)(C++20)(C++20)
    (C++23)
    (C++23)
    Formatting arguments
    (C++20)
    (C++20)
    (C++20)(C++20)(C++20)
    (C++20) (deprecated in C++26)
    (C++20)(C++20)
    Format error
    (C++20)
     
    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.

    2) 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.
    3) 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.

    Member types

    Type Definition
    iterator OutputIt
    char_type CharT

    Member alias templates

    Type Definition
    formatter_type<T> std::formatter<T, CharT>

    Member functions

    (constructor)
    [deleted]
    		 basic_format_context cannot be constructed by user code
    (public member function)
    operator=
    [deleted]
    		 basic_format_context is not assignable
    (public member function)
    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_context::arg

    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::basic_format_context::locale

    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.

    std::basic_format_context::out

    iterator 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.

    Example

    This section is incomplete
    Reason: no example

    Defect reports

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