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Asynchronous Operations: Utility Functions

Async can be used effectively with the basic, built in infrastructure in HHVM, along with some HSL functions. This basic infrastructure includes:

However, there are cases when we want to convert some collection of values to awaitables or we want to filter some awaitables out of a collection of awaitables. These types of scenarios come up when we are creating multiple awaitables to await in parallel. Some of the functions that help with this are:

Name	Returns	Description
`HH\Lib\Vec\filter_async<Tv>`	`Awaitable<vec<Tv>>`	Returns a new vec containing only the values for which the given async predicate returns `true`.
`HH\Lib\Vec\from_async<Tv>`	`Awaitable<vec<Tv>>`	Returns a new vec with each value awaited in parallel.
`HH\Lib\Vec\map_async<Tv1, Tv2>`	`Awaitable<vec<Tv2>>`	Returns a new vec where each value is the result of calling the given async function on the original value.
`HH\Lib\Dict\filter_async<Tk as arraykey, Tv>`	`Awaitable<dict<Tk,Tv>>`	Returns a new dict containing only the values for which the given async predicate returns `true`.
`HH\Lib\Dict\filter_with_key_async<Tk as arraykey, Tv>`	`Awaitable<dict<Tk,Tv>>`	Like `filter_async`, but lets you utilize the keys of your dict too.
`HH\Lib\Dict\from_async<Tk, Tv1>`	`Awaitable<dict<Tk,Tv2>>`	Returns a new dict where each value is the result of calling the given async function on the original value.
`HH\Lib\Dict\from_keys_async<Tk as arraykey, Tv>`	`Awaitable<dict<Tk,Tv>>`	Returns a new dict where each value is the result of calling the given async function on the corresponding key.
`HH\Lib\Dict\map_async<Tk as arraykey, Tv1, Tv2>`	`Awaitable<dict<Tk,Tv2>>`	Returns a new dict where each value is the result of calling the given async function on the original value.
`HH\Lib\Keyset\filter_async<Tv as arraykey>`	`Awaitable<keyset<Tv>>`	Returns a new keyset containing only the values for which the given async predicate returns `true`.
`HH\Lib\Keyset\from_async<Tv as arraykey>`	`Awaitable<keyset<Tv>>`	Returns a new keyset containing the awaited result of the given Awaitables.
`HH\Lib\Keyset\map_async<Tv, Tk as arraykey>`	`Awaitable<keyset<Tk>>`	Returns a new keyset where the value is the result of calling the given async function on the original values in the given traversable.

Other Convenience Functions

There are three convenience-functions tailored for use with async. They are:

Name	Returns	Description
`HH\Asio\usleep(int)`	`Awaitable<void>`	Wait a given length of time before an async function does more work.
`HH\Asio\later()`	`Awaitable<void>`	Reschedule the work of an async function until some undetermined point in the future.
`HH\Asio\wrap(Awaitable<Tv>)`	`Awaitable<ResultOrExceptionWrapper<Tv>>`	Wrap an `Awaitable` into an `Awaitable` of `ResultOrExceptionWrapper`.

Await As An ExpressionAsynchronous Operations:

ExtensionsAsynchronous Operations:

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