Reader - BHC Documentation

type Reader r = ReaderT r Identity { } #

newtype ReaderT r m a { } #

ReaderT { runReaderT :: r -> m a }

The reader monad transformer.

class Monad m => MonadReader r m { } #

askM :: m r

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

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

Class for monads with a readable environment.

runReader :: (Reader r a) -> r -> a { } #

O(1). Run a Reader computation with the given environment.

mapReader :: (a -> b) -> (Reader r a) -> Reader r b { } #

O(1). Map the return value of a Reader.

withReader :: (r' -> r) -> (Reader r a) -> Reader r' a { } #

O(1). Execute a Reader with a modified environment.

<*> :: { } #

>>= :: { } #

mapReaderT :: ((m a) -> n b) -> (ReaderT r m a) -> ReaderT r n b { } #

Map the inner computation.

withReaderT :: (r' -> r) -> (ReaderT r m a) -> ReaderT r' m a { } #

Transform the environment.

ask :: (Monad m) => ReaderT r m r { } #

O(1). Retrieve the entire environment.

local :: (r -> r) -> (ReaderT r m a) -> ReaderT r m a { } #

O(1). Execute a computation with a modified environment.

asks :: (Monad m) => (r -> a) -> ReaderT r m a { } #

O(1). Retrieve a function of the environment.

reader :: (Monad m) => (r -> a) -> ReaderT r m a { } #

O(1). Embed a simple reader action into the monad.

instance Functor m => Functor (ReaderT r m) { }

instance MonadTrans (ReaderT r) { }

instance MonadIO m => MonadIO (ReaderT r m) { }

instance Monad m => MonadReader r (ReaderT r m) { }