|Reactive behaviors (continuous time)
Reactive behaviors. They can be understood in terms of a simple
model (denotational semantics) as functions of time, namely at ::
BehaviorG t a -> (t -> a).
The semantics of BehaviorG instances are given by corresponding
instances for the semantic model (functions). See
- Functor: at (fmap f r) == fmap f (at r), i.e., fmap f r at
t == f (r at t).
- Applicative: at (pure a) == pure a, and at (s <*> r) == at s
<*> at t. That is, pure a at t == a, and (s <*> r) at t
== (s at t) (r at t).
- Monad: at (return a) == return a, and at (join rr) == join (at
. at rr). That is, return a at t == a, and join rr at t ==
(rr at t) at t. As always, (r >>= f) == join (fmap f r).
at (r >>= f) == at r >>= at . f.
- Monoid: a typical lifted monoid. If o is a monoid, then
Reactive o is a monoid, with mempty == pure mempty, and mappend
== liftA2 mappend. That is, mempty at t == mempty, and (r
mappend s) at t == (r at t) mappend (s at t).
Note: The signatures of all of the behavior functions can be generalized. Is
the interface generality worth the complexity?
The identity generalized behavior. Has value t at time t.
time :: Behavior TimeT
|stepper :: a -> EventI t a -> BehaviorI t a||Source|
Discretely changing behavior, based on an initial value and a
stepper :: a -> Event a -> Behavior a
Switch between behaviors.
switcher :: Behavior a -> Event (Behavior a) -> Behavior a
|snapshotWith :: Ord t => (a -> b -> c) -> BehaviorI t b -> EventI t a -> EventI t c||Source|
Snapshots a behavior whenever an event occurs and combines the values
using the combining function passed. Take careful note of the order of
arguments and results.
snapshotWith :: (a -> b -> c) -> Behavior b -> Event a -> Event c
|snapshot :: Ord t => BehaviorI t b -> EventI t a -> EventI t (a, b)||Source|
Snapshot a behavior whenever an event occurs. See also
snapshotWith. Take careful note of the order of arguments and
snapshot :: Event a -> Behavior b -> Event (a,b)
|snapshot_ :: Ord t => BehaviorI t b -> EventI t a -> EventI t b||Source|
Like snapshot but discarding event data (often a is '()').
snapshot_ :: Event a -> Behavior b -> Event b
|whenE :: Ord t => EventI t a -> BehaviorI t Bool -> EventI t a||Source|
Filter an event according to whether a reactive boolean is true.
whenE :: Event a -> Behavior Bool -> Event a
|accumB :: a -> EventI t (a -> a) -> BehaviorI t a||Source|
Behavior from an initial value and an updater event. See also
accumB :: a -> Event (a -> a) -> Behavior a
Like scanl for behaviors. See also scanlE.
scanlB :: forall a. (Behavior a -> Behavior a -> Behavior a) -> Behavior a
-> Event (Behavior a) -> Behavior a
Accumulate values from a monoid-valued event. Specialization of
scanlB, using mappend and mempty. See also monoidE.
monoidB :: Monoid a => Event (Behavior a) -> Behavior a
|maybeB :: Ord t => EventI t a -> EventI t b -> BehaviorI t (Maybe a)||Source|
Start out blank (Nothing), latching onto each new a, and blanking
on each b. If you just want to latch and not blank, then use
mempty for the second event.
maybeB :: Event a -> Event b -> Behavior (Maybe a)
|flipFlop :: Ord t => EventI t a -> EventI t b -> BehaviorI t Bool||Source|
Flip-flopping behavior. Turns true whenever first event occurs and
false whenever the second event occurs.
flipFlop :: Event a -> Event b -> Behavior Bool
|countB :: (Ord t, Num n) => EventI t a -> BehaviorI t n||Source|
Count occurrences of an event. See also countE.
countB :: Num n => Event a -> Behavior n
Like sum for behaviors.
sumB :: AdditiveGroup a => Event a -> Behavior a
integral :: (VectorSpace v, Scalar v ~ TimeT) =>
Event () -> Behavior v -> Behavior v
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