Instances.hs

-- |
-- Module:     Control.ContStuff.Instances
-- Copyright:  (c) 2010 Ertugrul Soeylemez
-- License:    BSD3
-- Maintainer: Ertugrul Soeylemez <es@ertes.de>
-- Stability:  experimental
--
-- This module implements some miscellaneous type class instances.

{-# LANGUAGE TypeFamilies #-}

module Control.ContStuff.Instances () where

import qualified Control.Exception as E
import Control.ContStuff.Classes
import Control.ContStuff.Trans
import Control.Monad.Trans.Class


----------------
-- Exceptions --
----------------

instance HasExceptions (Either e) where
    type Exception (Either e) = e
    raise = Left
    try = Right

instance HasExceptions Maybe where
    type Exception Maybe = ()
    raise = const Nothing
    try = Just . maybe (Left ()) Right

instance HasExceptions IO where
    type Exception IO = E.SomeException
    raise = E.throwIO
    try = E.try


--------------
-- Readable --
--------------

instance (Monad m, Readable m) => Readable (ChoiceT r i m) where
    type StateOf (ChoiceT r i m) = StateOf m
    get = lift get

instance (Monad m, Readable m) => Readable (ContT r m) where
    type StateOf (ContT r m) = StateOf m
    get = lift get

instance (Monad m, Readable m) => Readable (EitherT r e m) where
    type StateOf (EitherT r e m) = StateOf m
    get = lift get

instance (Monad m, Readable m) => Readable (IdentityT m) where
    type StateOf (IdentityT m) = StateOf m
    get = lift get

instance (Monad m, Readable m) => Readable (MaybeT r m) where
    type StateOf (MaybeT r m) = StateOf m
    get = lift get


--------------
-- Stateful --
--------------

instance (Monad m, Stateful m) => Stateful (ChoiceT r i m) where
    put = lift . put
    putLazy = lift . putLazy

instance (Monad m, Stateful m) => Stateful (ContT r m) where
    put = lift . put
    putLazy = lift . putLazy

instance (Monad m, Stateful m) => Stateful (EitherT r e m) where
    put = lift . put
    putLazy = lift . putLazy

instance (Monad m, Stateful m) => Stateful (IdentityT m) where
    put = lift . put
    putLazy = lift . putLazy

instance (Monad m, Stateful m) => Stateful (MaybeT r m) where
    put = lift . put
    putLazy = lift . putLazy