Copyright	(c) Ivan Perez and Manuel Baerenz 2016
License	BSD3
Maintainer	ivan.perez@keera.co.uk
Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Monad.Trans.MSF.Reader

Contents

Reader MSF running and wrapping.

Description

MSFs with a Reader monadic layer.

This module contains functions to work with MSFs that include a Reader monadic layer. This includes functions to create new MSFs that include an additional layer, and functions to flatten that layer out of the MSF's transformer stack.

Synopsis

newtype ReaderT r (m :: Type -> Type) a = ReaderT {
- runReaderT :: r -> m a
}
type Reader r = ReaderT r Identity
runReader :: Reader r a -> r -> a
mapReader :: (a -> b) -> Reader r a -> Reader r b
withReader :: (r' -> r) -> Reader r a -> Reader r' a
mapReaderT :: (m a -> n b) -> ReaderT r m a -> ReaderT r n b
withReaderT :: forall r' r (m :: Type -> Type) a. (r' -> r) -> ReaderT r m a -> ReaderT r' m a
ask :: forall (m :: Type -> Type) r. Monad m => ReaderT r m r
local :: forall r (m :: Type -> Type) a. (r -> r) -> ReaderT r m a -> ReaderT r m a
reader :: forall (m :: Type -> Type) r a. Monad m => (r -> a) -> ReaderT r m a
asks :: forall (m :: Type -> Type) r a. Monad m => (r -> a) -> ReaderT r m a
readerS :: Monad m => MSF m (r, a) b -> MSF (ReaderT r m) a b
runReaderS :: Monad m => MSF (ReaderT r m) a b -> MSF m (r, a) b
runReaderS_ :: Monad m => MSF (ReaderT s m) a b -> s -> MSF m a b

Documentation

newtype ReaderT r (m :: Type -> Type) 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.

Constructors

ReaderT
Fields runReaderT :: r -> m a

Instances

Instances details

MonadSplit g m => MonadSplit g (ReaderT r m)
Instance details Defined in Control.Monad.Random.Class Methods getSplit :: ReaderT r m g #
Generic1 (ReaderT r m :: Type -> Type)
Instance details Defined in Control.Monad.Trans.Reader Associated Types type Rep1 (ReaderT r m) :: k -> Type # Methods from1 :: forall (a :: k). ReaderT r m a -> Rep1 (ReaderT r m) a # to1 :: forall (a :: k). Rep1 (ReaderT r m) a -> ReaderT r m a #
MonadBase b m => MonadBase b (ReaderT r m)
Instance details Defined in Control.Monad.Base Methods liftBase :: b α -> ReaderT r m α #
MonadTrans (ReaderT r)
Instance details Defined in Control.Monad.Trans.Reader Methods lift :: Monad m => m a -> ReaderT r m a #
MonadInterleave m => MonadInterleave (ReaderT r m)
Instance details Defined in Control.Monad.Random.Class Methods interleave :: ReaderT r m a -> ReaderT r m a #
MonadRandom m => MonadRandom (ReaderT r m)
Instance details Defined in Control.Monad.Random.Class Methods getRandomR :: Random a => (a, a) -> ReaderT r m a # getRandom :: Random a => ReaderT r m a # getRandomRs :: Random a => (a, a) -> ReaderT r m [a] # getRandoms :: Random a => ReaderT r m [a] #
MonadFail m => MonadFail (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods fail :: String -> ReaderT r m a #
MonadFix m => MonadFix (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods mfix :: (a -> ReaderT r m a) -> ReaderT r m a #
MonadIO m => MonadIO (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods liftIO :: IO a -> ReaderT r m a #
MonadZip m => MonadZip (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods mzip :: ReaderT r m a -> ReaderT r m b -> ReaderT r m (a, b) # mzipWith :: (a -> b -> c) -> ReaderT r m a -> ReaderT r m b -> ReaderT r m c # munzip :: ReaderT r m (a, b) -> (ReaderT r m a, ReaderT r m b) #
Contravariant m => Contravariant (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods contramap :: (a' -> a) -> ReaderT r m a -> ReaderT r m a' # (>$) :: b -> ReaderT r m b -> ReaderT r m a #
Alternative m => Alternative (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods empty :: ReaderT r m a # (<\|>) :: ReaderT r m a -> ReaderT r m a -> ReaderT r m a # some :: ReaderT r m a -> ReaderT r m [a] # many :: ReaderT r m a -> ReaderT r m [a] #
Applicative m => Applicative (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods pure :: a -> ReaderT r m a # (<>) :: ReaderT r m (a -> b) -> ReaderT r m a -> ReaderT r m b # liftA2 :: (a -> b -> c) -> ReaderT r m a -> ReaderT r m b -> ReaderT r m c # (>) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m b # (<*) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m a #
Functor m => Functor (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods fmap :: (a -> b) -> ReaderT r m a -> ReaderT r m b # (<$) :: a -> ReaderT r m b -> ReaderT r m a #
Monad m => Monad (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods (>>=) :: ReaderT r m a -> (a -> ReaderT r m b) -> ReaderT r m b # (>>) :: ReaderT r m a -> ReaderT r m b -> ReaderT r m b # return :: a -> ReaderT r m a #
MonadPlus m => MonadPlus (ReaderT r m)
Instance details Defined in Control.Monad.Trans.Reader Methods mzero :: ReaderT r m a # mplus :: ReaderT r m a -> ReaderT r m a -> ReaderT r m a #
Generic (ReaderT r m a)
Instance details Defined in Control.Monad.Trans.Reader Associated Types type Rep (ReaderT r m a) :: Type -> Type # Methods from :: ReaderT r m a -> Rep (ReaderT r m a) x # to :: Rep (ReaderT r m a) x -> ReaderT r m a #
type Rep1 (ReaderT r m :: Type -> Type)
Instance details Defined in Control.Monad.Trans.Reader type Rep1 (ReaderT r m :: Type -> Type) = D1 ('MetaData "ReaderT" "Control.Monad.Trans.Reader" "transformers-0.6.1.0" 'True) (C1 ('MetaCons "ReaderT" 'PrefixI 'True) (S1 ('MetaSel ('Just "runReaderT") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) ((FUN 'Many r :: Type -> Type) :.: Rec1 m)))
type Rep (ReaderT r m a)
Instance details Defined in Control.Monad.Trans.Reader type Rep (ReaderT r m a) = D1 ('MetaData "ReaderT" "Control.Monad.Trans.Reader" "transformers-0.6.1.0" 'True) (C1 ('MetaCons "ReaderT" 'PrefixI 'True) (S1 ('MetaSel ('Just "runReaderT") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (r -> m a))))

type Reader r = ReaderT 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.

runReader #

Arguments

:: Reader r a	A `Reader` to run.
-> r	An initial environment.
-> a

Runs a Reader and extracts the final value from it. (The inverse of reader.)

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

Transform the value returned by a Reader.

runReader (mapReader f m) = f . runReader m

withReader #

Arguments

:: (r' -> r)	The function to modify the environment.
-> Reader r a	Computation to run in the modified environment.
-> Reader r' a

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

runReader (withReader f m) = runReader m . f

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

Transform the computation inside a ReaderT.

runReaderT (mapReaderT f m) = f . runReaderT m

withReaderT #

Arguments

:: forall r' r (m :: Type -> Type) a. (r' -> r)	The function to modify the environment.
-> ReaderT r m a	Computation to run in the modified environment.
-> ReaderT r' m a

Execute a computation in a modified environment (a more general version of local).

runReaderT (withReaderT f m) = runReaderT m . f

ask :: forall (m :: Type -> Type) r. Monad m => ReaderT r m r #

Fetch the value of the environment.

local #

Arguments

:: forall r (m :: Type -> Type) a. (r -> r)	The function to modify the environment.
-> ReaderT r m a	Computation to run in the modified environment.
-> ReaderT r m a

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

runReaderT (local f m) = runReaderT m . f

reader :: forall (m :: Type -> Type) r a. Monad m => (r -> a) -> ReaderT r m a #

Constructor for computations in the reader monad (equivalent to asks).

asks #

Arguments

:: forall (m :: Type -> Type) r a. Monad m
=> (r -> a)	The selector function to apply to the environment.
-> ReaderT r m a

Retrieve a function of the current environment.

```
asks f = liftM f ask
```

`Reader` `MSF` running and wrapping.

readerS :: Monad m => MSF m (r, a) b -> MSF (ReaderT r m) a b Source #

Build an MSF in the Reader monad from one that takes the reader environment as an extra input. This is the opposite of runReaderS.

runReaderS :: Monad m => MSF (ReaderT r m) a b -> MSF m (r, a) b Source #

Build an MSF that takes an environment as an extra input from one on the Reader monad. This is the opposite of readerS.

runReaderS_ :: Monad m => MSF (ReaderT s m) a b -> s -> MSF m a b Source #

Build an MSF function that takes a fixed environment as additional input, from an MSF in the Reader monad.

Documentation

Instances

Reader MSF running and wrapping.

`Reader` `MSF` running and wrapping.