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 futures 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.)After this call, every input future is no longer valid; every input shared_future remains valid.
[edit] 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 futures and shared_futures 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).
