std:: basic_format_parse_context
|
Defined in header
<format>
|
||
|
template
<
class
CharT
>
class basic_format_parse_context ; |
(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
std::basic_format_parse_context
instance is passed to
Formatter
when parsing the format specification.
A program that declares an explicit or partial specialization of
std::basic_format_parse_context
is ill-formed, no diagnostic required.
Several typedefs for common character types are provided:
|
Defined in header
<format>
|
|
| Type | Definition |
std::format_parse_context
|
std :: basic_format_parse_context < char > |
std::wformat_parse_context
|
std :: basic_format_parse_context < wchar_t > |
Member types
| Type | Definition |
char_type
|
CharT
|
iterator
|
std:: basic_string_view < CharT > :: const_iterator |
const_iterator
|
std:: basic_string_view < CharT > :: const_iterator |
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) |
|
check_dynamic_spec
(C++26)
|
checks if the type of the corresponding format argument with the given argument index is in the given type template arguments
(public member function) |
|
check_dynamic_spec_integral
(C++26)
|
checks if the type of the corresponding format argument with the given argument index is an integral type
(public member function) |
|
check_dynamic_spec_string
(C++26)
|
checks if the type of the corresponding format argument with the given argument index is a string type
(public member function) |
std::basic_format_parse_context:: basic_format_parse_context
| (1) | ||
|
constexpr
explicit
basic_format_parse_context
(
std::
basic_string_view
<
CharT
>
fmt,
|
(until C++26) | |
|
constexpr
explicit
basic_format_parse_context ( std:: basic_string_view < CharT > fmt ) noexcept ; |
(since C++26) | |
|
basic_format_parse_context
(
const
basic_format_parse_context
&
)
=
delete
;
|
(2) | |
std::basic_format_parse_context
instance. Initializes the format string range to
[
fmt.
begin
(
)
,
fmt.
end
(
)
)
, and the argument count to
num_args
(until C++26)
0
(since C++26)
.
|
Any call to
|
(since C++26) |
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 .
If the next argument index is larger than or equal to the num_args provided in the constructor, the call is not a core constant expression.
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 num_args provided in the constructor, the call is not a core constant expression.
std::basic_format_parse_context:: check_dynamic_spec
|
template
<
class
...
Ts
>
constexpr void check_dynamic_spec ( std:: size_t id ) noexcept ; |
(since C++26) | |
If id is larger than or equal to the num_args provided in the constructor or the type of the corresponding format argument (after conversion to std::basic_format_arg ) is not one of the types in Ts... , the call is not a core constant expression. A call to check_dynamic_spec has no effect at runtime.
-
- This overload participates in overload resolution only if the types in Ts... are unique and each type is one of bool , char_type , int , unsigned int , long long int , unsigned long long int , float , double , long double , const char_type * , std:: basic_string_view < char_type > , or const void * .
std::basic_format_parse_context:: check_dynamic_spec_integral
|
constexpr
void
check_dynamic_spec_integral
(
std::
size_t
id
)
noexcept
;
|
(since C++26) | |
Equivalent to call check_dynamic_spec < int , unsigned int , long long int , unsigned long long int > ( id ) . A call to check_dynamic_spec_integral has no effect at runtime.
std::basic_format_parse_context:: check_dynamic_spec_string
|
constexpr
void
check_dynamic_spec_string
(
std::
size_t
id
)
noexcept
;
|
(since C++26) | |
Equivalent to call check_dynamic_spec < const char_type * , std:: basic_string_view < char_type >> ( id ) . A call to check_dynamic_spec_string has no effect at runtime.
Example
|
This section is incomplete
Reason: no example |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3825 | C++20 |
check_arg_id
has a compile-time argument
id check, but
next_arg_id
did not have
|
added |
| LWG 3975 | C++20 |
user specialization of
basic_format_parse_context
was allowed
|
disallowed |