gistfile1.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

import Control.Monad.State
import Control.Monad.Trans
  
-- Stuff from haskeline.  MonadException is something that haskeline requires for whatever reason.
class MonadIO m => MonadException m
newtype InputT m a = InputT (m a) deriving (Monad, MonadIO)

myInputFunc :: MonadException m => InputT m (Maybe String)
myInputFunc = undefined

-- Stuff from my own transformer.  This requires that m be MonadIO because it needs to store state to disk
data FitState = FitState
newtype FitStateT m a = FitStateT (StateT FitState m a) deriving (Monad, MonadTrans)

myFitStateFunc :: MonadIO m => FitStateT m ()
myFitStateFunc = undefined

-- End result, which was not ideal.
myMainRoutineFunc :: (MonadException m, MonadIO m) => FitStateT (InputT m) ()
myMainRoutineFunc = do
  myFitStateFunc
  lift $ myInputFunc
  return ()