Control.Monad.Trans.Choice.Invariant

Documentation

newtype ChoiceT f m a

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)

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)

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)

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)

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)

Defined in Control.Monad.Trans.Choice.Invariant

Methods

choose :: f a -> ChoiceT f m a

MonadTrans (ChoiceT f)

ChoiceT is a functor on the category of monads. However it is an invariant functor. Meaning the traditional mapChoiceT cannot be implemented.

Defined in Control.Monad.Trans.Choice.Invariant

Methods

lift :: Monad m => m a -> ChoiceT f m a

Monad m => Monad (ChoiceT f m)

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)

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)

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)

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)

Defined in Control.Monad.Trans.Choice.Invariant

Methods

liftIO :: IO a -> ChoiceT f m a

Contravariant m => Contravariant (ChoiceT f m)

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)

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)

Defined in Control.Monad.Trans.Choice.Invariant

Methods

invmap :: (a -> b) -> (b -> a) -> ChoiceT f m a -> ChoiceT f m b

runChoiceT

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

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.