Copyright	(c) Eamon Olive 2020 (c) Louis Hyde 2020
License	AGPL-3
Maintainer	ejolive97@gmail.com
Stability	experimental
Safe Haskell	Safe
Language	Haskell2010

Control.Monad.Trans.Choice.Invariant

Description

Synopsis

newtype ChoiceT f m a = ChoiceT ((forall x. f x -> m x) -> m a)
runChoiceT :: (forall x. f x -> m x) -> ChoiceT f m a -> m a
invmapChoiceT :: (forall x. n x -> m x) -> (m a -> n b) -> ChoiceT f m a -> ChoiceT f n b

Documentation

newtype ChoiceT f m a Source #

The choice monad transformer It takes a monad and enriches it with choice.

Constructors

ChoiceT ((forall x. f x -> m x) -> m a)

Instances

MonadWriter w m => MonadWriter w (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods writer :: (a, w) -> ChoiceT f m a # tell :: w -> ChoiceT f m () # listen :: ChoiceT f m a -> ChoiceT f m (a, w) # pass :: ChoiceT f m (a, w -> w) -> ChoiceT f m a #
MonadState s m => MonadState s (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods get :: ChoiceT f m s # put :: s -> ChoiceT f m () # state :: (s -> (a, s)) -> ChoiceT f m a #
MonadReader r m => MonadReader r (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods ask :: ChoiceT f m r # local :: (r -> r) -> ChoiceT f m a -> ChoiceT f m a # reader :: (r -> a) -> ChoiceT f m a #
MonadError e m => MonadError e (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods throwError :: e -> ChoiceT f m a # catchError :: ChoiceT f m a -> (e -> ChoiceT f m a) -> ChoiceT f m a #
Monad m => MonadChoice f (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods choose :: f a -> ChoiceT f m a Source #
MonadTrans (ChoiceT f) Source #	`ChoiceT` is a functor on the category of monads. However it is an invariant functor. Meaning the traditional `mapChoiceT` cannot be implemented.
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods lift :: Monad m => m a -> ChoiceT f m a #
Monad m => Monad (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods (>>=) :: ChoiceT f m a -> (a -> ChoiceT f m b) -> ChoiceT f m b # (>>) :: ChoiceT f m a -> ChoiceT f m b -> ChoiceT f m b # return :: a -> ChoiceT f m a # fail :: String -> ChoiceT f m a #
Functor m => Functor (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods fmap :: (a -> b) -> ChoiceT f m a -> ChoiceT f m b # (<$) :: a -> ChoiceT f m b -> ChoiceT f m a #
Applicative m => Applicative (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods pure :: a -> ChoiceT f m a # (<>) :: ChoiceT f m (a -> b) -> ChoiceT f m a -> ChoiceT f m b # liftA2 :: (a -> b -> c) -> ChoiceT f m a -> ChoiceT f m b -> ChoiceT f m c # (>) :: ChoiceT f m a -> ChoiceT f m b -> ChoiceT f m b # (<*) :: ChoiceT f m a -> ChoiceT f m b -> ChoiceT f m a #
MonadPlus m => MonadPlus (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods mzero :: ChoiceT f m a # mplus :: ChoiceT f m a -> ChoiceT f m a -> ChoiceT f m a #
MonadIO m => MonadIO (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods liftIO :: IO a -> ChoiceT f m a #
Contravariant m => Contravariant (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods contramap :: (a -> b) -> ChoiceT f m b -> ChoiceT f m a # (>$) :: b -> ChoiceT f m b -> ChoiceT f m a #
Alternative m => Alternative (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods empty :: ChoiceT f m a # (<\|>) :: ChoiceT f m a -> ChoiceT f m a -> ChoiceT f m a # some :: ChoiceT f m a -> ChoiceT f m [a] # many :: ChoiceT f m a -> ChoiceT f m [a] #
Invariant m => Invariant (ChoiceT f m) Source #
Instance details Defined in Control.Monad.Trans.Choice.Invariant Methods invmap :: (a -> b) -> (b -> a) -> ChoiceT f m a -> ChoiceT f m b #

runChoiceT Source #

Arguments

:: (forall x. f x -> m x)

A chooser which can perform selections over fs containing arbitrary xs. This will be used to determine the result of each selection.

This type proves the theorem :

chooser (fmap f x) = fmap f (chooser x)

-> ChoiceT f m a

A monad transformed by ChoiceT to contain choices

-> m a

The initial monad with the ChoiceT removed and thus the choices resolved.

Use a chooser to perform all the selections of a ChoiceT. This uses a sensible argument order unlike many of the other monad transformers.

invmapChoiceT :: (forall x. n x -> m x) -> (m a -> n b) -> ChoiceT f m a -> ChoiceT f n b Source #

Transforms the computation inside the ChoiceT. This function differs from other map functions over the monads in monad transformers in that it requires an additional function of type forall x . n x -> m x. This is because ChoiceT is not a covariant functor over the category of monads, but rather an invariant functor.