zio-rows.hs

newtype ZIO r a
  = ZIO (ReaderT r IO a)
  deriving newtype (Functor, Applicative, Monad, MonadIO)

unZIO :: ZIO r a -> ReaderT r IO a
unZIO (ZIO z) = z

runZIO :: ZIO r a -> (r | r1) -> IO a
runZIO (ZIO z) r = runReaderT z r

accessM :: (t -> ZIO (l :: t | r) a) -> ZIO (l :: t | r) a
accessM f = ZIO (ReaderT (\r -> runReaderT (unZIO (f r#l)) r))

data Console
  = Console
  { _printLine :: String -> ZIO Console ()
  , _readLine  :: ZIO Console String
  }

printLine :: String -> ZIO (console :: Console | r) ()
printLine s = accessM (flip _printLine s)

readLine :: ZIO (console :: Console | r) String
readLine = accessM _readLine

data Beep
  = Beep
  { _beep :: ZIO Beep ()
  }

beep :: ZIO (beep :: Beep | r) ()
beep = accessM f
  where f env = _beep env#beep

type Env = (console :: Console, beep :: Beep |)

type App a = ZIO Env a