# FRP.Event

- Package
- purescript-hyrule
- Repository
- mikesol/purescript-hyrule

### #keepLatest Source

`keepLatest :: forall a. Event (Event a) -> Event a`

Flatten a nested `Event`

, reporting values only from the most recent
inner `Event`

.

### #sampleOnRight Source

`sampleOnRight :: forall a b. Event a -> Event (a -> b) -> Event b`

Create an `Event`

which samples the latest values from the first event
at the times when the second event fires.

### #Backdoor Source

`type Backdoor = { bus :: Bus, create :: Create, createO :: CreateO, createPure :: CreatePure, createPureO :: CreatePureO, delay :: Delay, hot :: Hot, mailbox :: Mailbox, mailboxed :: Mailboxed, makeEvent :: MakeEvent, makeEventO :: MakeEventO, makeLemmingEvent :: MakeLemmingEvent, makeLemmingEventO :: MakeLemmingEventO, makePureEvent :: MakePureEvent, memoize :: Memoize, subscribe :: Subscribe, subscribeO :: SubscribeO, subscribePure :: SubscribePure, subscribePureO :: SubscribePureO }`

### #CreatePureOT Source

`type CreatePureOT = forall a r. ST r (PureEventIO' r a)`

### #CreatePureT Source

`type CreatePureT = forall a r. ST r (PureEventIO r a)`

### #Event Source

`newtype Event a`

An `Event`

represents a collection of discrete occurrences with associated
times. Conceptually, an `Event`

is a (possibly-infinite) list of values-and-times:

```
type Event a = List { value :: a, time :: Time }
```

Events are created from real events like timers or mouse clicks, and then combined using the various functions and instances provided in this module.

Events are consumed by providing a callback using the `subscribe`

function.

#### Instances

### #MailboxedT Source

`type MailboxedT = forall r a b. Ord a => Event { address :: a, payload :: b } -> ((a -> Event b) -> r) -> Event r`

### #MakeLemmingEventOT Source

`type MakeLemmingEventOT = forall a r. STFn2 Subscriber (STFn1 a r Unit) r (ST r Unit) -> Event a`

### #PureEventIO Source

`type PureEventIO :: Region -> Type -> Type`

`type PureEventIO r a = { event :: Event a, push :: a -> ST r Unit }`

### #PureEventIO' Source

`type PureEventIO' :: Region -> Type -> Type`

`type PureEventIO' r a = { event :: Event a, push :: STFn1 a r Unit }`

### #Subscriber Source

`newtype Subscriber`

#### Constructors

### #createPure Source

`createPure :: CreatePureT`

Create an event and a function which supplies a value to that event in ST.

### #mailboxed Source

`mailboxed :: MailboxedT`

Takes the entire domain of a and allows for ad-hoc specialization.

### #makeEvent Source

`makeEvent :: MakeEventT`

Make an `Event`

from a function which accepts a callback and returns an
unsubscription function.

Note: you probably want to use `create`

instead, unless you need explicit
control over unsubscription.

### #makePureEvent Source

`makePureEvent :: MakePureEventT`

Make a pure `Event`

from a function which accepts a callback and returns an
unsubscription function.

Note: you probably want to use `create`

instead, unless you need explicit
control over unsubscription.

### #subscribe Source

`subscribe :: SubscribeT`

Subscribe to an `Event`

by providing a callback.

`subscribe`

returns a canceller function.

### #subscribeO Source

`subscribeO :: SubscribeOT`

Subscribe to an `Event`

by providing a callback.

`subscribe`

returns a canceller function.

## Re-exports from **FRP.**Event.Class

### #Filterable Source

`class Filterable :: (Type -> Type) -> Constraint`

`class (Compactable f, Functor f) <= Filterable f where`

`Filterable`

represents data structures which can be *partitioned*/*filtered*.

`partitionMap`

- partition a data structure based on an either predicate.`partition`

- partition a data structure based on boolean predicate.`filterMap`

- map over a data structure and filter based on a maybe.`filter`

- filter a data structure based on a boolean.

Laws:

Functor Relation:

`filterMap identity ≡ compact`

Functor Identity:

`filterMap Just ≡ identity`

Kleisli Composition:

`filterMap (l <=< r) ≡ filterMap l <<< filterMap r`

`filter ≡ filterMap <<< maybeBool`

`filterMap p ≡ filter (isJust <<< p)`

Functor Relation:

`partitionMap identity ≡ separate`

Functor Identity 1:

`_.right <<< partitionMap Right ≡ identity`

Functor Identity 2:

`_.left <<< partitionMap Left ≡ identity`

`f <<< partition ≡ partitionMap <<< eitherBool`

where`f = \{ no, yes } -> { left: no, right: yes }`

`f <<< partitionMap p ≡ partition (isRight <<< p)`

where`f = \{ left, right } -> { no: left, yes: right}`

Default implementations are provided by the following functions:

`partitionDefault`

`partitionDefaultFilter`

`partitionDefaultFilterMap`

`partitionMapDefault`

`filterDefault`

`filterDefaultPartition`

`filterDefaultPartitionMap`

`filterMapDefault`

#### Members

#### Instances

`Filterable Array`

`Filterable Maybe`

`(Monoid m) => Filterable (Either m)`

`Filterable List`

`(Ord k) => Filterable (Map k)`

### #IsEvent Source

`class IsEvent :: (Type -> Type) -> Constraint`

`class (Alternative event, Filterable event) <= IsEvent event where`

Functions which an `Event`

type should implement:

`fold`

: combines incoming values using the specified function, starting with the specific initial value.`keepLatest`

flattens a nested event, reporting values only from the most recent inner event.`sampleOn`

: samples an event at the times when a second event fires.`fix`

: compute a fixed point, by feeding output events back in as inputs.`bang`

: A one-shot event that happens NOW.

#### Members

`keepLatest :: forall a. event (event a) -> event a`

`sampleOnRight :: forall a b. event a -> event (a -> b) -> event b`

`fix :: forall i. (event i -> event i) -> event i`

### #sampleOnRight_ Source

`sampleOnRight_ :: forall event a b. IsEvent event => event a -> event b -> event a`

Create an `Event`

which samples the latest values from the first event
at the times when the second event fires, ignoring the values produced by
the second event.