Forever.purs

module Forever where

import Prelude

import Control.Monad.Eff
import Control.Monad.Eff.Console
import Control.Monad.Free
import Control.Monad.Rec.Class (forever)

import Data.NaturalTransformation

data TeletypeF a = PutStrLn String a

type Teletype a = Free TeletypeF a

putStrLn :: String -> Teletype Unit
putStrLn s = liftF (PutStrLn s unit)

teletypeN :: forall e. NaturalTransformation TeletypeF (Eff (console :: CONSOLE))
teletypeN (PutStrLn s a) = const a <$> pure s

run :: forall a. Teletype a -> Eff (console :: CONSOLE) a
run = foldFree teletypeN

program = forever $ putStrLn "Forever"

main = run program