std::experimental::promise<R>::promise (library fundamentals TS)
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< cpp | experimental | lib extensions | promise
promise(); |
(1) | (library fundamentals TS) |
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template
<
class Alloc >
promise( std::allocator_arg_t, const Alloc& alloc ) ; |
(2) | (library fundamentals TS) |
promise( promise&& other ) noexcept; |
(3) | (library fundamentals TS) |
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promise( const promise& other ) = delete;
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(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
3) Move constructor. Constructs the promise with the shared state of other using move semantics. After construction, other
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
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 ( ) |
| std::nullptr_t | The value of std::experimental::pmr::get_default_resource ( ) |
| 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
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| 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
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Exceptions
1,2) (none)