Control.Monad.Event.Classes

Documentation

class Monad m => MonadTime m t | m -> t where

A type-class for monads with a concept of time. That concept need not necessarily meet any prior conditions - not even an Eq instance.

Methods

getCurrentTime :: m t

Instances

Monad m => MonadTime (EventT t m) t

class Monad m => MonadSimControl m where

A monad in which there is a concept of running and not-running and unrestricted operations for switching between them.

Methods

resumeSimulation :: m ()

pauseSimulation :: m ()

isSimulationRunning :: m Bool

Instances

Monad m => MonadSimControl (EventT t m)

class Monad m => MonadEvent m e | e -> m where

A monad in which there is a concept of an "event" - an action with a sort of a special status, which can be described for humans and can be otherwise manipulated in monads implementing the classes to follow.

Methods

describeEvent :: e -> m Doc

runEvent :: e -> m ()

Instances

Monad m => MonadEvent m (AdHocEvent m)

MonadSimControl m => MonadEvent m (SimControl m)

(MonadIO m, RealFrac t, Pretty t) => MonadEvent (EventT t m) (SetDebugHandlers t m)

(Monad m, Pretty t) => MonadEvent (EventT t m) (EventDescriptor (EventT t m) t)

Monad m => MonadEvent (EventT t m) (EventT t m a)

class (MonadEvent m e, MonadTime m t) => ScheduleEvent m t e | m -> t, e -> m where

A monad which can schedule events for later execution. For obvious reasons, such a monad must also have a concept of events (covering the event that the user is trying to schedule) and a concept of time.

Methods

scheduleEventIn :: t -> e -> m EventID

Schedule an event for execution at a time (relative to the current time). The meaning of "relative to" is left entirely up to the implementor, however it will generally be the case that time is an instance of Num and that "relative to" means something along the lines of "at now + _".

Returns an EventID that can be used to identify the event if needed later (for example, to cancel it).

doNext :: e -> m ()

schedule an event to run at the current time. This does not constitute a promise to execute immediately or in any particular order relative to other events that have been or will be scheduled for the current time.

If an implementor has a time type which is an instance of Num, then doNext should be equivalent to scheduleEventIn 0 - unless the monad's documentation clearly warns to the contrary in a really big typeface. ; ) Note that this clause may change to also strongly suggest that doNext put its event at the very front of the queue (ie, before any other events already scheduled for the current time).

Instances

(Monad m, Ord t, Num t, MonadEvent (EventT t m) e) => ScheduleEvent (EventT t m) t e

class MonadTime m t => CancelEvent m t | m -> t where

A monad in which an event (presumably one previously scheduled) can be canceled.

Methods

cancelEvent :: EventID -> m (Maybe (EventDescriptor m t))

Cancel an event given its EventID. If successful (and if the monad's implementation allows it), an EventDescriptor (an existential wrapper describing an event, its ID, and the time at which it would have run) containing the canceled event is returned.

Instances

(Monad m, Ord t) => CancelEvent (EventT t m) t

class MonadTime m t => GetCurrentEvent m t | m -> t where

A monad in which an EventDescriptor for the currently-executing event, if any, can be obtained.

Methods

getCurrentEvent :: m (Maybe (EventDescriptor m t))

Instances

Monad m => GetCurrentEvent (EventT t m) t

class MonadTime m t => RetryEvent m t | m -> t where

A monad in which the currently executing event can be rescheduled. Note that calling retryEventIn does not terminate the currently executing event - although perhaps it should. Until a more permanent decision is made, it's probably best to make retryEventIn the last action of an event when it is used, to minimize impact of future changes.

Methods

retryEventIn :: t -> m EventID

Instances

Monad m => RetryEvent (EventT t m) t

class MonadTime m t => MonadEventQueueInfo m t | m -> t where

A monad in which information about the event queue can be retrieved.

Methods

eventQueueSize :: m Int

Return the number of events currently scheduled.

eventQueueContents :: m [EventDescriptor m t]

Return a list of (some or all of) the events coming up. There is no obligation on the part of the monad to provide anything at all.

Instances

(Monad m, Ord t) => MonadEventQueueInfo (EventT t m) t