# std::experimental::future<T>::future

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< cpp‎ | experimental‎ | future

future() noexcept; | (1) |
future( std::experimental::future<T>&& f ) noexcept; | (2) |
future( const std::experimental::future<T>& ) = delete; | (3) |
future( std::experimental::future<std::experimental::future<T>> && other ) noexcept; | (4) |

1) Default constructor. Constructs an empty `future` object that does not refer to a shared state.
2) Constructs a `future` object, transferring the shared state held by f, if any. After construction, f.valid() is false.
3) Copy constructor is deleted. `future` cannot be copied.
4) Unwrapping constructor. Constructs a `future` object from the shared state referred to by other, if any. If other.valid() == false prior to this call, the constructed `future` object is empty. Otherwise, the resulting `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 `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 `future` object.

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

### Parameters

f | - | another future object to initialize with
other | - | a `std::experimental::future` object to unwrap

### 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 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::future<T>`)

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