Control.Monad.Trans.MultiReader

The multi-valued version of mtl's Reader / ReaderT / MonadReader

MultiReaderT

newtype MultiReaderT x m a

A Reader transformer monad patameterized by:

• x - The list of types constituting the environment / input (to be read),
• m - The inner monad.

MultiReaderT corresponds to mtl's ReaderT, but can contain a heterogenous list of types.

This heterogenous list is represented using Types.Data.List, i.e:

• '[] - The empty list,
• a ': b - A list where a is an arbitrary type and b is the rest list.

For example,

MultiReaderT '[Int, Bool] :: (* -> *) -> (* -> *)

is a Reader transformer containing the types [Int, Bool].

Constructors

MultiReaderT

Fields

runMultiReaderTRaw :: StateT (HList x) m a

Instances

MonadState s m => MonadState s (MultiReaderT c m)

MonadWriter w m => MonadWriter w (MultiReaderT c m)

(Monad m, ContainsType a c) => MonadMultiReader a (MultiReaderT c m)

MonadTrans (MultiReaderT x)

Monad m => Monad (MultiReaderT x m)

Functor f => Functor (MultiReaderT x f)

MonadFix m => MonadFix (MultiReaderT r m)

(Applicative m, Monad m) => Applicative (MultiReaderT x m)

type MultiReaderTNull = MultiReaderT []

A MultiReader transformer carrying an empty state.

type MultiReader x = MultiReaderT x Identity

A reader monad parameterized by the list of types x of the environment / input to carry.

Similar to Reader r = ReaderT r Identity

MonadMultiReader class

class Monad m => MonadMultiReader a m where

All methods must be defined.

The idea is: Any monad stack is instance of MonadMultiReader a, iff the stack contains a MultiReaderT x with a element of x.

Methods

mAsk

Arguments

:: m a

Access to a specific type in the environment.

Instances

(MonadTrans t, Monad (t m), MonadMultiReader a m) => MonadMultiReader a (t m)

(Monad m, ContainsType a c) => MonadMultiReader a (MultiReaderT c m)

(Monad m, ContainsType a c) => MonadMultiReader a (MultiReaderT c m)

(Monad m, ContainsType a r) => MonadMultiReader a (MultiRWST r w s m)

(Monad m, ContainsType a r) => MonadMultiReader a (MultiRWST r w s m)

run-functions

runMultiReaderT :: Monad m => HList r -> MultiReaderT r m a -> m a

runMultiReaderT_ :: Functor m => HList r -> MultiReaderT r m a -> m ()

runMultiReaderTNil :: Monad m => MultiReaderT [] m a -> m a

runMultiReaderTNil_ :: Functor m => MultiReaderT [] m a -> m ()

with-functions (single Reader)

withMultiReader :: Monad m => r -> MultiReaderT (r : rs) m a -> MultiReaderT rs m a

withMultiReader_ :: (Functor m, Monad m) => r -> MultiReaderT (r : rs) m a -> MultiReaderT rs m ()

with-functions (multiple Readers)

withMultiReaders :: Monad m => HList r1 -> MultiReaderT (Append r1 r2) m a -> MultiReaderT r2 m a

withMultiReaders_ :: (Functor m, Monad m) => HList r1 -> MultiReaderT (Append r1 r2) m a -> MultiReaderT r2 m ()

inflate-function (run ReaderT in MultiReaderT)

inflateReader :: (Monad m, ContainsType r rs) => ReaderT r m a -> MultiReaderT rs m a

other functions

mapMultiReaderT :: (m (a, HList w) -> m' (a', HList w)) -> MultiReaderT w m a -> MultiReaderT w m' a'

Map both the return value and the environment of a computation using the given function.

Note that there is a difference to mtl's ReaderT, where it is not possible to modify the environment.

mGetRaw :: Monad m => MultiReaderT a m (HList a)

A raw extractor of the contained HList (i.e. the complete Reader).

mPutRaw :: Monad m => HList s -> MultiReaderT s m ()