Algebra.Monad.Reader

The Reader monad

class Monad m => MonadReader r m | m -> r where

Methods

ask :: m r

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

Instances

MonadReader r ((->) r)

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

Monad m => MonadReader r (ReaderT r m)

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

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

data ReaderT r m a

A simple Reader monad

Instances

MonadWriter w m => MonadWriter w (ReaderT r m)

Monad m => MonadReader r (ReaderT r m)

MonadState s m => MonadState s (ReaderT r m)

MonadTrans (ReaderT r)

MonadInternal (ReaderT r)

Unit m => Unit (ReaderT r m)

MonadCont m => MonadCont (ReaderT r m)

MonadList m => MonadList (ReaderT r m)

MonadFix m => MonadFix (ReaderT r m)

Monad m => Monad (ReaderT r m)

Monad m => Applicative (ReaderT r m)

Functor m => Functor (ReaderT r m)

Ring (m (a, Void, Void)) => Ring (ReaderT r m a)

Monoid (m (a, Void, Void)) => Monoid (ReaderT r m a)

Semigroup (m (a, Void, Void)) => Semigroup (ReaderT r m a)

type Reader r a = ReaderT r Id a

_readerT :: (Functor m, Functor m') => Iso (ReaderT r m a) (ReaderT r' m' b) (r -> m a) (r' -> m' b)

_reader :: Iso (Reader r a) (Reader r' b) (r -> a) (r' -> b)