The (abstract) type of event streams.

Denotationally, one can think of an eventstream a value of type

[(Time,a)]

Where the points in time are non-strictly increasing. There can be multiple simulatinous events in an event stream.

Obtain the next element of the event stream. The obtained event is guaranteed to lie in the future.

Obtain all simultaneous next elements of the event stream. The obtained event is guaranteed to lie in the future.

The empty event stream

Merge two event stream.

In case of simultaneity, the left elements come first

Collapses each set simultanious events into a single event carrying the list of occurances.

Get the event stream of changes to the input behavior.

Get the events that the behavior changes from False to True

Turns an event of an event stream into an event stream.

A left scan over an event stream

Right fold over an eventstream

The result of folding over the rest of the event stream is in an event, since it can be only known in the future.

No initial value needs to be given, since the initial value is never

Right fold over an eventstream with a left initial value

Defined as:

foldriEv i f ev =  f i <$> foldrEv f es

Create a behavior from an initial value and a event stream of updates.

Start with the argument behavior, and switch to a new behavior each time an event in the event stream occurs.

Defined as:

foldrSwitch b = foldriEv b switch

Left fold over an eventstream to create a behavior (behavior depends on when the fold started).

Yet another type of fold.

Defined as:

foldBs b f es = scanlEv f b es >>= foldrSwitch b

Filter the Just values from an event stream.

Filter events from an event stream

Shorthand for

filterMapEs f e = catMaybesEs $ f <$> e

Shorthand for

filterMapEs b e = catMaybesEs $ b <@@> e

Filter events from an eventstream based on a function that changes over time

Obtain only the events from input stream that occur while the input behavior is True

An event stream with only elements that occur before the argument event.

Sample the behavior each time an event in the stream occurs, and combine the outcomes.

Sample the behavior each time an event in the stream occurs.

Delay a behavior by one tick of the `clock'.

The event stream functions as the `clock': the input behavior is sampled on each event, and the current value of the output behavior is always the previously sample.

Occasionally useful to prevent immediate feedback loops.

Create an event stream that has an event each time the returned function is called. The function can be called from any thread.

Call the given function each time an event occurs, and execute the resulting Now computation

Execute the given IO action each time an event occurs. The IO action is executed on the main thread, so it should not take a long time.

Debug function, print all values in the event stream to stderr, prepended with the given string.