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std::basic_format_parse_context

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< cpp‎ | utility‎ | format
 
 
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Formatting library
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basic_format_parse_contextformat_parse_contextwformat_parse_context
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Formatting arguments
Format error
 
Defined in header <format>
template<class CharT>
class basic_format_parse_context;
(1) (since C++20)
using format_parse_context = basic_format_parse_context<char>;
(2) (since C++20)
using wformat_parse_context = basic_format_parse_context<wchar_t>;
(3) (since C++20)

Provides access to the format string parsing state consisting of the format string range being parsed and the argument counter for automatic indexing.

A basic_format_parse_context instance is passed to Formatter when parsing the format specification.

Contents

[edit] Member types

Type Definition
char_type CharT
iterator std::basic_string_view<CharT>::const_iterator
const_iterator std::basic_string_view<CharT>::const_iterator

[edit] Member functions

(constructor)
constructs a std::basic_format_parse_context instance from format string and argument count
(public member function)
operator=
[deleted]
std::basic_format_parse_context is not copyable
(public member function)
begin
returns an iterator to the beginning of the format string range
(public member function)
end
returns an iterator to the end of the format string range
(public member function)
advance_to
advances the begin iterator to the given position
(public member function)
next_arg_id
enters automatic indexing mode, and returns the next argument index
(public member function)
check_arg_id
enters manual indexing mode, checks if the given argument index is in range
(public member function)

std::basic_format_parse_context::basic_format_parse_context

constexpr explicit basic_format_parse_context(std::basic_string_view<CharT> fmt,
                                              std::size_t num_args = 0) noexcept;
(1)
basic_format_parse_context(const basic_format_parse_context&) = delete;
(2)
1) Constructs a std::basic_format_parse_context instance. Initializes the format string range to [fmt.begin(), fmt.end()), and the argument count to num_args.
2) The copy constructor is deleted. std::basic_format_parse_context is not copyable.

std::basic_format_parse_context::begin

constexpr const_iterator begin() const noexcept;

Returns an iterator to the beginning of the format string range.

std::basic_format_parse_context::end

constexpr const_iterator end() const noexcept;

Returns an iterator to the end of the format string range.

std::basic_format_parse_context::advance_to

constexpr void advance_to(const_iterator it);

Sets the beginning of the format string range to it. After a call to advance_to, subsequent calls to begin() will return a copy of it.

The behavior is undefined if end() is not reachable from it.

std::basic_format_parse_context::next_arg_id

constexpr std::size_t next_arg_id();

Enters automatic argument indexing mode, and returns the next argument index, starting from 0.

If *this has already entered manual argument indexing mode, throws std::format_error.

std::basic_format_parse_context::check_arg_id

constexpr void check_arg_id(std::size_t id);

Enters manual argument indexing mode.

If *this has already entered automatic argument indexing mode, throws std::format_error.

If id is larger than or equal to the argument count provided in the constructor, the call is not a constant expression.

[edit] Example

[edit] See also