module Control.Monad.Readers
( module Control.Monad.Trans.Reader
, MonadReaders(askPoly, localPoly, readerPoly)
, viewPoly
) where
import Control.Lens
import Control.Monad.Trans.Cont as Cont
import Control.Monad.Trans.Except
import Control.Monad.Trans.Error
import Control.Monad.Trans.Identity
import Control.Monad.Trans.List
import Control.Monad.Trans.Maybe
import Control.Monad.Trans.Reader (ReaderT)
import qualified Control.Monad.Trans.Reader as ReaderT (ask, local, reader)
import qualified Control.Monad.Trans.RWS.Lazy as LazyRWS (RWST, ask, local, reader)
import qualified Control.Monad.Trans.RWS.Strict as StrictRWS (RWST, ask, local, reader)
import Control.Monad.Trans.State.Lazy as Lazy
import Control.Monad.Trans.State.Strict as Strict
import Control.Monad.Trans.Writer.Lazy as Lazy
import Control.Monad.Trans.Writer.Strict as Strict
import Control.Monad.Trans.Class (lift)
import Data.Monoid
class Monad m => MonadReaders r m where
askPoly :: m r
localPoly :: (r -> r) -> m a -> m a
readerPoly :: (r -> a)
-> m a
readerPoly f = do
r <- askPoly :: m r
return (f r)
viewPoly :: forall r m a. MonadReaders r m => Getting a r a -> m a
viewPoly lns = (askPoly :: m r) >>= return . view lns
instance Monad m => MonadReaders r (ReaderT r m) where
askPoly = ReaderT.ask
localPoly = ReaderT.local
readerPoly = ReaderT.reader
instance MonadReaders r ((->) r) where
askPoly = id
localPoly f m = m . f
readerPoly = id
instance (Monad m, Monoid w) => MonadReaders r (LazyRWS.RWST r w s m) where
askPoly = LazyRWS.ask
localPoly = LazyRWS.local
readerPoly = LazyRWS.reader
instance (Monad m, Monoid w) => MonadReaders r (StrictRWS.RWST r w s m) where
askPoly = StrictRWS.ask
localPoly = StrictRWS.local
readerPoly = StrictRWS.reader
instance MonadReaders r' m => MonadReaders r' (ContT r m) where
askPoly = lift askPoly
localPoly = Cont.liftLocal askPoly localPoly
readerPoly = lift . readerPoly
instance (Error e, MonadReaders r m) => MonadReaders r (ErrorT e m) where
askPoly = lift askPoly
localPoly = mapErrorT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (ExceptT e m) where
askPoly = lift askPoly
localPoly = mapExceptT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (IdentityT m) where
askPoly = lift askPoly
localPoly = mapIdentityT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (ListT m) where
askPoly = lift askPoly
localPoly = mapListT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (MaybeT m) where
askPoly = lift askPoly
localPoly = mapMaybeT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (Lazy.StateT s m) where
askPoly = lift askPoly
localPoly = Lazy.mapStateT . localPoly
readerPoly = lift . readerPoly
instance MonadReaders r m => MonadReaders r (Strict.StateT s m) where
askPoly = lift askPoly
localPoly = Strict.mapStateT . localPoly
readerPoly = lift . readerPoly
instance (Monoid w, MonadReaders r m) => MonadReaders r (Lazy.WriterT w m) where
askPoly = lift askPoly
localPoly = Lazy.mapWriterT . localPoly
readerPoly = lift . readerPoly
instance (Monoid w, MonadReaders r m) => MonadReaders r (Strict.WriterT w m) where
askPoly = lift askPoly
localPoly = Strict.mapWriterT . localPoly
readerPoly = lift . readerPoly