Control.Monad.Readers

MonadState without the function dependency m -> s.

Documentation

module Control.Monad.Trans.Reader

class Monad m => MonadReaders r m where

Minimal complete definition

askPoly, localPoly

Methods

askPoly :: m r

localPoly :: (r -> r) -> m a -> m a

readerPoly

Arguments

:: (r -> a)

The selector function to apply to the environment.

-> m a

Retrieves a function of the current environment.

Instances

MonadReaders r m => MonadReaders r (MaybeT m)

MonadReaders r m => MonadReaders r (ListT m)

MonadReaders r m => MonadReaders r (IdentityT m)

MonadReaders r ((->) r)

(Monoid w, MonadReaders r m) => MonadReaders r (WriterT w m)

(Monoid w, MonadReaders r m) => MonadReaders r (WriterT w m)

MonadReaders r m => MonadReaders r (StateT s m)

MonadReaders r m => MonadReaders r (StateT s m)

MonadReaders r m => MonadReaders r (ExceptT e m)

(Error e, MonadReaders r m) => MonadReaders r (ErrorT e m)

MonadReaders r' m => MonadReaders r' (ContT r m)

Modiifed copies of instances from mtl.

Monad m => MonadReaders r (ReaderT r m)

(Monad m, Monoid w) => MonadReaders r (RWST r w s m)

(Monad m, Monoid w) => MonadReaders r (RWST r w s m)

viewPoly :: forall r m a. MonadReaders r m => Getting a r a -> m a

Modified view function that works if there is a MonadReaders r instance