Control.Monad.Trans.Identity

The identity monad transformer.

This is useful for functions parameterized by a monad transformer.

The identity monad transformer

newtype IdentityT f a

The trivial monad transformer, which maps a monad to an equivalent monad.

Constructors

IdentityT

Fields

• runIdentityT :: f a

Instances

MonadTrans (IdentityT *)

Methods

lift :: Monad m => m a -> IdentityT * m a

Monad m => Monad (IdentityT * m)

Methods

(>>=) :: IdentityT * m a -> (a -> IdentityT * m b) -> IdentityT * m b

(>>) :: IdentityT * m a -> IdentityT * m b -> IdentityT * m b

return :: a -> IdentityT * m a

fail :: String -> IdentityT * m a

Functor m => Functor (IdentityT * m)

Methods

fmap :: (a -> b) -> IdentityT * m a -> IdentityT * m b

(<$) :: a -> IdentityT * m b -> IdentityT * m a

MonadFix m => MonadFix (IdentityT * m)

Methods

mfix :: (a -> IdentityT * m a) -> IdentityT * m a

MonadFail m => MonadFail (IdentityT * m)

Methods

fail :: String -> IdentityT * m a

Applicative m => Applicative (IdentityT * m)

Methods

pure :: a -> IdentityT * m a

(<*>) :: IdentityT * m (a -> b) -> IdentityT * m a -> IdentityT * m b

(*>) :: IdentityT * m a -> IdentityT * m b -> IdentityT * m b

(<*) :: IdentityT * m a -> IdentityT * m b -> IdentityT * m a

Foldable f => Foldable (IdentityT * f)

Methods

fold :: Monoid m => IdentityT * f m -> m

foldMap :: Monoid m => (a -> m) -> IdentityT * f a -> m

foldr :: (a -> b -> b) -> b -> IdentityT * f a -> b

foldr' :: (a -> b -> b) -> b -> IdentityT * f a -> b

foldl :: (b -> a -> b) -> b -> IdentityT * f a -> b

foldl' :: (b -> a -> b) -> b -> IdentityT * f a -> b

foldr1 :: (a -> a -> a) -> IdentityT * f a -> a

foldl1 :: (a -> a -> a) -> IdentityT * f a -> a

toList :: IdentityT * f a -> [a]

null :: IdentityT * f a -> Bool

length :: IdentityT * f a -> Int

elem :: Eq a => a -> IdentityT * f a -> Bool

maximum :: Ord a => IdentityT * f a -> a

minimum :: Ord a => IdentityT * f a -> a

sum :: Num a => IdentityT * f a -> a

product :: Num a => IdentityT * f a -> a

Traversable f => Traversable (IdentityT * f)

Methods

traverse :: Applicative f => (a -> f b) -> IdentityT * f a -> f (IdentityT * f b)

sequenceA :: Applicative f => IdentityT * f (f a) -> f (IdentityT * f a)

mapM :: Monad m => (a -> m b) -> IdentityT * f a -> m (IdentityT * f b)

sequence :: Monad m => IdentityT * f (m a) -> m (IdentityT * f a)

Eq1 f => Eq1 (IdentityT * f)

Methods

liftEq :: (a -> b -> Bool) -> IdentityT * f a -> IdentityT * f b -> Bool

Ord1 f => Ord1 (IdentityT * f)

Methods

liftCompare :: (a -> b -> Ordering) -> IdentityT * f a -> IdentityT * f b -> Ordering

Read1 f => Read1 (IdentityT * f)

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (IdentityT * f a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [IdentityT * f a]

Show1 f => Show1 (IdentityT * f)

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> IdentityT * f a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [IdentityT * f a] -> ShowS

MonadZip m => MonadZip (IdentityT * m)

Methods

mzip :: IdentityT * m a -> IdentityT * m b -> IdentityT * m (a, b)

mzipWith :: (a -> b -> c) -> IdentityT * m a -> IdentityT * m b -> IdentityT * m c

munzip :: IdentityT * m (a, b) -> (IdentityT * m a, IdentityT * m b)

MonadIO m => MonadIO (IdentityT * m)

Methods

liftIO :: IO a -> IdentityT * m a

Alternative m => Alternative (IdentityT * m)

Methods

empty :: IdentityT * m a

(<|>) :: IdentityT * m a -> IdentityT * m a -> IdentityT * m a

some :: IdentityT * m a -> IdentityT * m [a]

many :: IdentityT * m a -> IdentityT * m [a]

MonadPlus m => MonadPlus (IdentityT * m)

Methods

mzero :: IdentityT * m a

mplus :: IdentityT * m a -> IdentityT * m a -> IdentityT * m a

(Eq1 f, Eq a) => Eq (IdentityT * f a)

Methods

(==) :: IdentityT * f a -> IdentityT * f a -> Bool

(/=) :: IdentityT * f a -> IdentityT * f a -> Bool

(Ord1 f, Ord a) => Ord (IdentityT * f a)

Methods

compare :: IdentityT * f a -> IdentityT * f a -> Ordering

(<) :: IdentityT * f a -> IdentityT * f a -> Bool

(<=) :: IdentityT * f a -> IdentityT * f a -> Bool

(>) :: IdentityT * f a -> IdentityT * f a -> Bool

(>=) :: IdentityT * f a -> IdentityT * f a -> Bool

max :: IdentityT * f a -> IdentityT * f a -> IdentityT * f a

min :: IdentityT * f a -> IdentityT * f a -> IdentityT * f a

(Read1 f, Read a) => Read (IdentityT * f a)

Methods

readsPrec :: Int -> ReadS (IdentityT * f a)

readList :: ReadS [IdentityT * f a]

readPrec :: ReadPrec (IdentityT * f a)

readListPrec :: ReadPrec [IdentityT * f a]

(Show1 f, Show a) => Show (IdentityT * f a)

Methods

showsPrec :: Int -> IdentityT * f a -> ShowS

show :: IdentityT * f a -> String

showList :: [IdentityT * f a] -> ShowS

mapIdentityT :: (m a -> n b) -> IdentityT m a -> IdentityT n b

Lift a unary operation to the new monad.

Lifting other operations

liftCatch :: Catch e m a -> Catch e (IdentityT m) a

Lift a catchE operation to the new monad.

liftCallCC :: CallCC m a b -> CallCC (IdentityT m) a b

Lift a callCC operation to the new monad.