Events.Events

Events and combinators for them.

Documentation

data Result

Constructors

Immediate

Awaiting (IO ())

AwaitingAlways (IO ())

newtype Event a

Constructors

Event (Toggle -> (IO a -> IO ()) -> IO Result)

Instances

Monad Event

HasEvent Event

class HasEvent eventType where

HasEvent represents those event-like things which can be converted to an event.

Methods

toEvent :: eventType a -> Event a

Instances

HasEvent Event

Guard guard => HasEvent (GuardedEvent guard)

never :: Event a

The event that never happens

always :: IO a -> Event a

The event that always happens, immediately

sync :: Event a -> IO a

Synchronise on an event, waiting on it until it happens, then returning the attached value.

poll :: Event a -> IO (Maybe a)

Synchronise on an event, but return immediately with Nothing if it can't be satisfied at once.

(>>>=) :: Event a -> (a -> IO b) -> Event b

Attach an action to be done after the event occurs.

(>>>) :: Event a -> IO b -> Event b

Attach an action to be done after the event occurs.

(+>) :: Event a -> Event a -> Event a

Choose between two events. The first one takes priority.

choose :: [Event a] -> Event a

Choose between a list of events.

tryEV :: Event a -> Event (Either Exception a)

Catch an error if it occurs during an action attached to an event.

computeEvent :: IO (Event a) -> Event a

Construct a new event using an action which is called at each synchronisation

wrapAbort :: IO (Event a, IO ()) -> Event a

When we synchronise on wrapAbort preAction preAction is evaluated to yield (event,postAction). Then exactly one of the following: (1) thr event is satisfied, and postAction is not done. (2) some other event in this synchronisation is satisfied (so this one isn't), and postAction is done. (3) no event is satisfied (and so we will deadlock).

noWait :: Event a -> Event ()

Turns an event into one which is always satisfied at once but registers the value to be done later. WARNING - only to be used with events without actions attached, as any actions will not get done. noWait is typically used with send events, where we don't want to wait for someone to pick up the value.

class HasSend chan where

HasSend represents things like channels on which we can send values

Methods

send :: chan a -> a -> Event ()

Instances

HasSend Channel

HasSend (GuardedChannel guard)

class HasReceive chan where

HasReceive represents things like channels from which we can take values.

Methods

receive :: chan a -> Event a

Instances

HasReceive Channel

Guard guard => HasReceive (GuardedChannel guard)

sendIO :: HasSend chan => chan a -> a -> IO ()

Send a value along a channel (as an IO action)

receiveIO :: HasReceive chan => chan a -> IO a

Get a value from a channel (as an IO action)

allowWhile :: Event () -> Event a -> Event a

allowWhile event1 event2 waits for event2, while handling event1.

data Request a b

Constructors

Request (a -> IO (Event b, IO ()))

request :: Request a b -> a -> IO b

doRequest :: Request a b -> a -> IO (Event b, IO ())

spawnEvent :: Event () -> IO (IO ())

Synchronise on an event in a different thread. The kill action it returns is unsafe since it can cause deadlocks if it occurs at an awkward moment. To avoid this use spawnEvent, if possible.

getAllQueued :: Event a -> IO [a]

get all we can get from the event without waiting.

thenGetEvent :: Event a -> (a -> Event b) -> Event b

thenEvent :: Event a -> Event b -> Event b

doneEvent :: a -> Event a

syncNoWait :: Event a -> IO ()

Register an event as synchronised but don't wait for it to complete. WARNING - only to be used with events without actions attached, as any actions will not get done. noWait is typically used with send events, where we don't want to wait for someone to pick up the value. synchronise on something without waiting