FRP.Behavior

type Behavior = ABehavior (AnEvent Effect)

A Behavior acts like a continuous function of time.

We can construct a sample a Behavior from some Event, combine Behaviors using Applicative, and sample a final Behavior on some other Event.

newtype ABehavior :: (Type -> Type) -> Type -> Typenewtype ABehavior event a

ABehavior is the more general type of Behavior, which is parameterized over some underlying event type.

Normally, you should use Behavior instead, but this type can also be used with other types of events, including the ones in the Semantic module.

Instances

• (Functor event) => Functor (ABehavior event)
• (Functor event) => Apply (ABehavior event)
• (Functor event) => Applicative (ABehavior event)
• (Functor event, Semigroup a) => Semigroup (ABehavior event a)
• (Functor event, Monoid a) => Monoid (ABehavior event a)

behavior :: forall event a. (forall b. event (a -> b) -> event b) -> ABehavior event a

Construct a Behavior from its sampling function.

step :: forall event a. IsEvent event => a -> event a -> ABehavior event a

Create a Behavior which is updated when an Event fires, by providing an initial value.

sample :: forall event a b. ABehavior event a -> event (a -> b) -> event b

Sample a Behavior on some Event.

sampleBy :: forall event a b c. Functor event => (a -> b -> c) -> ABehavior event a -> event b -> event c

Sample a Behavior on some Event by providing a combining function.

sample_ :: forall event a b. Functor event => ABehavior event a -> event b -> event a

Sample a Behavior on some Event, discarding the event's values.

gate :: forall event a. Filterable event => ABehavior event Boolean -> event a -> event a

Filter an Event by the boolean value of a Behavior.

gateBy :: forall event p a. Filterable event => (p -> a -> Boolean) -> ABehavior event p -> event a -> event a

Sample a Behavior on some Event by providing a predicate function.

unfold :: forall event a b. IsEvent event => (a -> b -> b) -> event a -> b -> ABehavior event b

Create a Behavior which is updated when an Event fires, by providing an initial value and a function to combine the current value with a new event to create a new value.

switcher :: forall event a. IsEvent event => ABehavior event a -> event (ABehavior event a) -> ABehavior event a

Switch Behaviors based on an Event.

integral :: forall event a t. IsEvent event => Field t => Semiring a => (((a -> t) -> t) -> a) -> a -> ABehavior event t -> ABehavior event a -> ABehavior event a

Integrate with respect to some measure of time.

This function approximates the integral using the trapezium rule at the implicit sampling interval.

The Semiring a should be a vector field over the field t. To represent this, the user should provide a grate which lifts a multiplication function on t to a function on a. Simple examples where t ~ a can use the integral' function instead.

integral' :: forall event t. IsEvent event => Field t => t -> ABehavior event t -> ABehavior event t -> ABehavior event t

Integrate with respect to some measure of time.

This function is a simpler version of integral where the function being integrated takes values in the same field used to represent time.

derivative :: forall event a t. IsEvent event => Field t => Ring a => (((a -> t) -> t) -> a) -> ABehavior event t -> ABehavior event a -> ABehavior event a

Differentiate with respect to some measure of time.

This function approximates the derivative using a quotient of differences at the implicit sampling interval.

The Semiring a should be a vector field over the field t. To represent this, the user should provide a grate which lifts a division function on t to a function on a. Simple examples where t ~ a can use the derivative' function.

derivative' :: forall event t. IsEvent event => Field t => ABehavior event t -> ABehavior event t -> ABehavior event t

Differentiate with respect to some measure of time.

This function is a simpler version of derivative where the function being differentiated takes values in the same field used to represent time.

solve :: forall t a. Field t => Semiring a => (((a -> t) -> t) -> a) -> a -> Behavior t -> (Behavior a -> Behavior a) -> Behavior a

Solve a first order differential equation of the form

da/dt = f a

by integrating once (specifying the initial conditions).

For example, the exponential function with growth rate ⍺:

exp = solve' 1.0 Time.seconds (⍺ * _)

solve' :: forall a. Field a => a -> Behavior a -> (Behavior a -> Behavior a) -> Behavior a

Solve a first order differential equation.

This function is a simpler version of solve where the function being integrated takes values in the same field used to represent time.

solve2 :: forall t a. Field t => Semiring a => (((a -> t) -> t) -> a) -> a -> a -> Behavior t -> (Behavior a -> Behavior a -> Behavior a) -> Behavior a

Solve a second order differential equation of the form

d^2a/dt^2 = f a (da/dt)

by integrating twice (specifying the initial conditions).

For example, an (damped) oscillator:

oscillate = solve2' 1.0 0.0 Time.seconds (\x dx -> -⍺ * x - δ * dx)

solve2' :: forall a. Field a => a -> a -> Behavior a -> (Behavior a -> Behavior a -> Behavior a) -> Behavior a

Solve a second order differential equation.

This function is a simpler version of solve2 where the function being integrated takes values in the same field used to represent time.

fixB :: forall event a. IsEvent event => a -> (ABehavior event a -> ABehavior event a) -> ABehavior event a

Compute a fixed point

animate :: forall scene. ABehavior (AnEvent Effect) scene -> (scene -> Effect Unit) -> Effect (Effect Unit)

Animate a Behavior by providing a rendering function.