std:: basic_format_context
|
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
&
>
.
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.
| 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 |
| LWG 3975 | C++20 |
user specialization of
basic_format_context
was allowed
|
disallowed |
| LWG 4061 | C++20 |
basic_format_context
was constructible and assignable by user code
|
made neither constructible nor assignable |