Reactive-banana – Safe and simple semantics

The third and final approach to FRP we'll take a look at is Reactive-banana. Like Yampa, we have both continuous- and discrete-time semantics at our disposal. In Reactive-banana terminology, events describe discrete time, while behaviors describe continuous time. Behaviors in Reactive-banana are like signals in Elerea. Historically, the names event and behavior were the first to occur:

data Event a    -- instance Functor
data Behavior a -- instance Functor, Applicative

Note that behavior is not Monad, unlike Elerea's signal, which did have a Monad instance. Instead, Reactive-banana supports moments as reactive computation contexts. There is a pure Moment monad, impure MomentIO monad and MonadMoment class that is used to overload moment context:

data Moment a     -- instance Monad, MonadFix, MonadMoment
data MomentIO a   –- instance ..., MonadIO

class Monad m => MonadMoment m where
    liftMoment :: Moment a -> m a...