reactive-banaa-simple.hs

import Reactive.Banana (compile)
import Reactive.Banana.Frameworks (newAddHandler, fromAddHandler, actuate, reactimate)
import Control.Concurrent (threadDelay, forkIO)
import Control.Monad (forever)
import Data.Char (toUpper)

main = do
    -- newAddHandler returns an AddHandler (roughly a callback) and a
    -- way to fire the callback (fire).
    (es, fire) <- newAddHandler

    -- We fire the handler with the value "hello" every 100 ms.
    forkIO $ forever $ do
        threadDelay (1000 * 100)
        fire "hello"

    -- Create a simple reactive network that prints the value passed
    -- to the callback, once as passed, then as uppercase.
    network <- compile $ do
        c <- fromAddHandler es
        reactimate $ fmap print c
        reactimate $ fmap print (fmap (map toUpper) c)

    -- actuate "activates" the network (registers callbacks etc.), can
    -- be paused with `pause`
    actuate network

    getLine >> return ()