Run this computation to obtain an A, then invoke the given callback.
Run this computation to obtain an A, then invoke the given callback.
Also see runAsync.
Run this computation to obtain an A, so long as cancel remains false.
Run this computation to obtain an A, so long as cancel remains false.
Because of trampolining, we get frequent opportunities to cancel
while stepping through the trampoline, so this should provide a fairly
robust means of cancellation.
Run this Future and block awaiting its result.
Run this Future, passing the result to the given callback once available.
Run this Future, passing the result to the given callback once available.
Any pure, non-asynchronous computation at the head of this Future will
be forced in the calling thread. At the first Async encountered, control
switches to whatever thread backs the Async and this function returns.
Run this computation to obtain an A, so long as cancel remains false.
Run this computation to obtain an A, so long as cancel remains false.
Because of trampolining, we get frequent opportunities to cancel
while stepping through the trampoline, this should provide a fairly
robust means of cancellation.
Begins running this Future and returns a new future that blocks
waiting for the result.
Begins running this Future and returns a new future that blocks
waiting for the result. Note that this results
Evaluate this Future to a result, or another asynchronous computation.
Evaluate this Future to a result, or another asynchronous computation.
This has the effect of stripping off any 'pure' trampolined computation at
the start of this Future.
Like step, but may be interrupted by setting cancel to true.
Like step, but may be interrupted by setting cancel to true.
Returns a Future which returns a TimeoutException after timeoutInMillis,
and attempts to cancel the running computation.
Returns a Future which returns a TimeoutException after timeoutInMillis,
and attempts to cancel the running computation.
This implementation will not block the future's execution thread
Futureis a trampolined computation producing anAthat may include asynchronous steps. LikeTrampoline, arbitrary monadic expressions involvingmapandflatMapare guaranteed to use constant stack space. But in addition, one may construct aFuturefrom an asynchronous computation, represented as a function,listen: (A => Unit) => Unit, which registers a callback that will be invoked when the result becomes available. This makesFutureuseful as a concurrency primitive and as a control structure for wrapping callback-based APIs with a more straightforward, monadic API.Unlike the
Futureimplementation in scala 2.10,mapandflatMapdo NOT spawn new tasks and do not require an implicitExecutionContext. Instead,mapandflatMapmerely add to the current (trampolined) continuation that will be run by the 'current' thread, unless explicitly forked viaFuture.forkorFuture.apply. This means thatFutureachieves much better thread reuse than the 2.10 implementation and avoids needless thread pool submit cycles.Futurealso differs from the scala 2.10Futuretype in that it does not necessarily represent a _running_ computation. Instead, we reintroduce nondeterminism _explicitly_ using the functions of thescalaz.Nondeterminsminterface. This simplifies our implementation and makes code easier to reason about, since the order of effects and the points of nondeterminism are made fully explicit and do not depend on Scala's evaluation order.IMPORTANT NOTE:
Futuredoes not include any error handling and should generally only be used as a building block by library writers who want to build onFuture's capabilities but wish to design their own error handling strategy. Seescalaz.concurrent.Taskfor a type that extendsFuturewith proper error handling -- it is merely a wrapper forFuture[Throwable \/ A]with a number of additional convenience functions.