std::experimental::when_any
Defined in header <experimental/future>
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template < class Sequence > struct when_any_result { |
(concurrency TS) | |
template < class InputIt > auto when_any(InputIt first, InputIt last) |
(1) | (concurrency TS) |
template < class... Futures > auto when_any(Futures&&... futures) |
(2) | (concurrency TS) |
Create a future object that becomes ready when at least one of the input future
s and shared_futures become ready. The behavior is undefined if any input future
or shared_future
is invalid.
In particular, let Sequence
be a std::vector<typename std::iterator_traits<InputIt>::value_type> for (1) and std::tuple<std::decay_t<Futures>...> for (2). This function template creates a shared state containing when_any_result<Sequence>
and returns a future referring to the shared state. Every input future
is moved into the corresponding object in the futures
member of the when_any_result<Sequence>
in the shared state, and every input shared_future
is copied to the corresponding object in the futures
member of the when_any_result<Sequence>
in the shared state. The order of the objects in the Sequence
matches the order of arguments.
InputIt
's value type (i.e., typename std::iterator_traits<InputIt>::value_type) is a std::experimental::future or std::experimental::shared_future.Fn
in Futures
, either std::remove_reference_t<Fn> is std::experimental::future<Rn>, or std::decay_t<Fn> is std::experimental::shared_future<Rn>.)After this call, every input future
is no longer valid; every input shared_future
remains valid.
Return value
A future
referring to the shared state created by the call. The future is always valid(), and it becomes ready when at least one of the input future
s and shared_future
s the call are ready. The index
member of the when_any_result
contains the position of the ready future
or shared_future
in the futures member.
future
is ready immediately; the futures
field of the when_any_result
is an empty vector, and the index
field is size_t(-1).future
is ready immediately; the futures
field of the when_any_result
is an empty tuple, and the index
field is size_t(-1).