lio-0.0.1: LIO/MonadLIO.hs

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE OverlappingInstances #-}

-- | This module provides a function 'liftLIO' for executing 'LIO'
-- computations from transformed versions of the 'LIO' monad.  There
-- is also a method @liftIO@, which is a synonym for 'liftLIO', to
-- help with porting code that expects to run in the 'IO' monad.
module LIO.MonadLIO where

import LIO.TCB

import Control.Monad.Trans (MonadTrans(..))

class (Monad m, Label l) => MonadLIO m l s | m -> l s where
    liftLIO :: LIO l s a -> m a
    liftIO  :: LIO l s a -> m a -- Might want to hide this one
    liftIO  = liftLIO

instance (Label l) => MonadLIO (LIO l s) l s where
    liftLIO = id

instance (MonadLIO m l s, MonadTrans t, Monad (t m)) => MonadLIO (t m) l s where
   liftLIO = lift . liftLIO