std::experimental::shared_future<T>::shared_future

 

C++

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Technical Specifications

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals 2 TS)

Extensions for parallelism (parallelism TS)

Extensions for parallelism 2 (parallelism TS v2)

Extensions for concurrency (concurrency TS)

Concepts (concepts TS)

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Extensions for concurrency

std::future extensions

experimental::future

experimental::shared_future

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std::experimental::shared_future

shared_future::shared_future

shared_future::operator=

shared_future::is_ready

shared_future::then

 

shared_future() noexcept;	(1)
shared_future(std::experimental::shared_future<T>&& f) noexcept;	(2)
shared_future(const std::experimental::shared_future<T>& f);	(3)
shared_future(std::experimental::future<std::experimental::shared_future<T>> && other) noexcept;	(4)
shared_future(std::experimental::future<T>&& f) noexcept;	(5)

1) Default constructor. Constructs an empty shared_future object that does not refer to a shared state.

2) Constructs a shared_future object, transferring the shared state held by f, if any. After construction, f.valid() is false.

3) Constructs a shared future that refers to the same shared state as f, if any.

4) Unwrapping constructor. Constructs a shared_future object from the shared state referred to by other, if any. If other.valid() == false prior to this call, the constructed shared_future object is empty. Otherwise, the resulting shared_future object becomes ready when one of the following happens:

• other and other.get() are both ready. The value or exception from other.get() is stored in the shared state associated with the resulting shared_future object.
• other is ready, but other.get() is invalid. An exception of type std::future_error with an error condition of std::future_errc::broken_promise is stored in the shared state associated with the resulting shared_future object.

After this constructor returns, valid() is equal to the value of other.valid() prior to this call, and other.valid() == false.

5) Constructs a shared_future object, transferring the shared state held by f, if any. After construction, f.valid() is false.

Parameters

f	-	another future object to initialize with
other	-	A std::experimental::future object to unwrap

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 2697	Concurrency TS	behavior of unwrapping constructor is unclear with an invalid future	constructs an empty future

See also

(constructor)

constructs the future object (public member function of std::shared_future<T>)