Control.Broccoli

Small experimental library for interactive functional programs.

Documentation

data X a

A value of type a that varies.

Instances

Functor X

Applicative X

data E a

An event that carries values of type a when it occurs.

Instances

Functor E

Monoid (E a)

never :: E a

An event that never happens.

snapshot :: E a -> X b -> E (a, b)

An event which gets the value of a signal when another event occurs.

snapshot_ :: E a -> X b -> E b

Like snapshot but ignores the original event's payload.

accumulate :: E a -> s -> (a -> s -> s) -> X s

Sum over events using an initial state and a state transition function.

edge :: X a -> (a -> a -> Maybe b) -> E b

An event that occurs when an edge is detected in a signal. The edge test is applied to values before and after a discrete transition in the signal. The test should return Nothing when the two values are the same.

justE :: E (Maybe a) -> E a

Filter out events with the value of Nothing.

maybeE :: (a -> Maybe b) -> E a -> E b

Filter out events using a Maybe function.

filterE :: (a -> Bool) -> E a -> E a

Filter out events using a Bool function.

data Setup a

A monad for hooking up inputs and outputs to a program.

Instances

Monad Setup

Functor Setup

Applicative Setup

runProgram :: Setup (IO (), E ()) -> IO ()

Run the setup action to create input and output threads. The returned IO action will be executed when setup is complete. runProgram blocks until the returned event occurs, at which time it kills all the threads and returns.

newX :: a -> Setup (X a, a -> IO ())

Creates a new signal and an IO action to update it. The argument is the initial value of the signal.

newE :: Setup (E a, a -> IO ())

Creates a new event and an IO action to trigger it.

input :: IO () -> Setup ()

Spawn an input thread to generate source signals and events.

output :: E a -> (a -> IO ()) -> Setup ()

Spawn a thread to execute an action for each event occurrence.

debugX :: (Eq a, Show a) => X a -> X a

Print out transitions in a signal. Only for debugging purposes.

debugE :: Show a => E a -> E a

Print out events as they occur. Only for debugging purposes.