Control.Monad.Trans.Ether.Reader

See Control.Monad.Trans.Reader.

The Reader monad

type Reader tag r = ReaderT tag r Identity

The parameterizable reader monad.

Computations are functions of a shared environment.

The return function ignores the environment, while >>= passes the inherited environment to both subcomputations.

reader :: Monad m => proxy tag -> (r -> a) -> ReaderT tag r m a

Constructor for computations in the reader monad (the inverse of runReader).

runReader :: proxy tag -> Reader tag r a -> r -> a

Runs a ReaderT with the given environment and returns the vinal value.

The ReaderT monad transformer

data ReaderT tag r m a

The reader monad transformer, which adds a read-only environment to the given monad.

The return function ignores the environment, while >>= passes the inherited environment to both subcomputations.

Instances

Monad m => MonadReader tag r (ReaderT tag r m)

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

MonadBase b m => MonadBase b (ReaderT tag r m)

MonadBaseControl b m => MonadBaseControl b (ReaderT tag r m)

MonadError e m => MonadError e (ReaderT tag r m)

MonadReader r' m => MonadReader r' (ReaderT tag r m)

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

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

MFunctor (ReaderT tag r)

MMonad (ReaderT tag r)

MonadTrans (ReaderT tag r)

MonadTransControl (ReaderT tag r)

LiftLocal (ReaderT tag r)

LiftCallCC (ReaderT tag r)

LiftPass (ReaderT tag r)

LiftListen (ReaderT tag r)

LiftCatch (ReaderT tag r)

Alternative m => Alternative (ReaderT tag r m)

Monad m => Monad (ReaderT tag r m)

Functor m => Functor (ReaderT tag r m)

MonadFix m => MonadFix (ReaderT tag r m)

MonadPlus m => MonadPlus (ReaderT tag r m)

Applicative m => Applicative (ReaderT tag r m)

MonadIO m => MonadIO (ReaderT tag r m)

MonadCont m => MonadCont (ReaderT tag r m)

Taggable (ReaderT tag r m)

Tagged (ReaderT tag r m) tag

Generic (ReaderT tag r m a)

Newtype (ReaderT tag r m a)

type StT (ReaderT tag r) a = StT (ReaderT r) a

type StT (ReaderT tag r) a = StT (ReaderT tag r) a

type Untagged (ReaderT tag r m) = ReaderT r m

type Tag (ReaderT tag r m) = Just * tag

type Inner (ReaderT tag r m) = Just (* -> *) m

type StM (ReaderT tag r m) a = ComposeSt (ReaderT tag r) m a

type Rep (ReaderT tag r m a)

type O (ReaderT tag r m a) = GO (Rep (ReaderT tag r m a))

readerT :: proxy tag -> (r -> m a) -> ReaderT tag r m a

Constructor for computations in the reader monad transformer.

runReaderT :: proxy tag -> ReaderT tag r m a -> r -> m a

Runs a ReaderT with the given environment and returns the vinal value.

Reader operations

ask :: Monad m => proxy tag -> ReaderT tag r m r

Fetch the value of the environment.

local

Arguments

:: proxy tag

-> (r -> r)

The function to modify the environment.

-> ReaderT tag r m a

Computation to run in the modified environment.

-> ReaderT tag r m a

Execute a computation in a modified environment (a specialization of withReaderT).

• runReaderT tag (local tag f m) = runReaderT tag m . f