{-# LANGUAGE FunctionalDependencies #-}

-- | Something.
class (MonadReader r s, MonadWriter w m) => MonadState s m | m -> s where

  get :: m s

  put :: s -> m ()

-- | 'MonadParsec'
class
  ( Stream s, -- Token streams
    MonadPlus m -- Potential for failure
    )
  => MonadParsec e s m
    | m -> e s where

  -- | 'getState' returns state
  getState
    :: m s

  -- | 'putState' sets state
  putState
    :: s
    -> m ()