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

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

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

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

MonadExcept tag e m => MonadExcept tag e (ReaderT tag' r m)

MonadWriter tag w m => MonadWriter tag w (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)

MonadTrans (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 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 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.

mapReaderT :: proxy tag -> (m a -> n b) -> ReaderT tag r m a -> ReaderT tag r n b

Transform the computation inside a ReaderT.

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

withReaderT

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 more general version of local).

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

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

Lifting other operations

liftCatch :: proxy tag -> Catch e m a -> Catch e (ReaderT tag r m) a

Lift a catchE operation to the new monad.

liftCallCC :: proxy tag -> CallCC m a b -> CallCC (ReaderT tag r m) a b

Lift a callCC operation to the new monad.