std::experimental::promise<R>:: promise (library fundamentals TS)
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<
cpp
|
experimental
|
lib extensions
|
promise
|
promise
(
)
;
|
(1) | (library fundamentals TS) |
|
template
<
class
Alloc
>
promise ( std:: allocator_arg_t , const Alloc & alloc ) ; |
(2) | (library fundamentals TS) |
|
promise
(
promise
&&
other
)
noexcept
;
|
(3) | (library fundamentals TS) |
|
promise
(
const
promise
&
other
)
=
delete
;
|
(4) | (library fundamentals TS) |
Constructs a
std::experimental::promise
object.
1)
Default constructor. Constructs the promise with an empty shared state.
2)
Constructs the promise with an empty shared state. The shared state is allocated using
alloc
, which is treated as a type-erased allocator (see below).
3)
Move constructor. Constructs the promise with the shared state of
other
using move semantics. After construction,
other
has no shared state.
4)
std::experimental::promise
is not copyable.
Type-erased allocator
The constructors of
promise
taking an allocator argument
alloc
treats that argument as a type-erased allocator. The memory resource pointer used by
promise
to allocate memory is determined using the allocator argument (if specified) as follows:
Type of
alloc
|
Value of the memory resource pointer |
| Non-existent (no allocator specified at time of construction) | The value of std:: experimental :: pmr :: get_default_resource ( ) at time of construction. |
| std::nullptr_t | The value of std:: experimental :: pmr :: get_default_resource ( ) at time of construction. |
|
A pointer type convertible to
std:: experimental :: pmr :: memory_resource * |
static_cast < std:: experimental :: pmr :: memory_resource * > ( alloc ) |
|
A specialization of
std::experimental::pmr::polymorphic_allocator |
alloc. resource ( ) |
| Any other type meeting the Allocator requirements |
A pointer to a value of type
std::
experimental
::
pmr
::
resource_adaptor
<
A
>
(
alloc
)
, where
A
is the type of
alloc
. The pointer remains valid only for the lifetime of the
promise
object.
|
| None of the above | The program is ill-formed. |
Parameters
| alloc | - | allocator to use to allocate the shared state |
| other | - |
another
std::experimental::promise
to acquire the state from
|
Exceptions
1,2)
(none)