Copyright	(c) 2007 Magnus Therning
License	BSD-style (see the file LICENSE)
Maintainer	R.Paterson@city.ac.uk
Stability	experimental
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Control.Monad.Trans.Identity

Contents

The identity monad transformer
Lifting other operations

Description

The identity monad transformer.

This is useful for functions parameterized by a monad transformer.

Synopsis

newtype IdentityT f a = IdentityT {
- runIdentityT :: f a
}
mapIdentityT :: (m a -> n b) -> IdentityT m a -> IdentityT n b
liftCatch :: Catch e m a -> Catch e (IdentityT m) a
liftCallCC :: CallCC m a b -> CallCC (IdentityT m) a b

The identity monad transformer

newtype IdentityT f a Source #

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

Constructors

IdentityT
Fields runIdentityT :: f a

Instances

MonadTrans (IdentityT :: (Type -> Type) -> Type -> Type) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods lift :: Monad m => m a -> IdentityT m a Source #
Monad m => Monad (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods fmap :: (a -> b) -> IdentityT m a -> IdentityT m b # (<$) :: a -> IdentityT m b -> IdentityT m a #
MonadFix m => MonadFix (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods mfix :: (a -> IdentityT m a) -> IdentityT m a #
MonadFail m => MonadFail (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods fail :: String -> IdentityT m a #
Applicative m => Applicative (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods pure :: a -> IdentityT m a # (<>) :: IdentityT m (a -> b) -> IdentityT m a -> IdentityT m b # liftA2 :: (a -> b -> c) -> IdentityT m a -> IdentityT m b -> IdentityT m c # (>) :: IdentityT m a -> IdentityT m b -> IdentityT m b # (<*) :: IdentityT m a -> IdentityT m b -> IdentityT m a #
Foldable f => Foldable (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods traverse :: Applicative f0 => (a -> f0 b) -> IdentityT f a -> f0 (IdentityT f b) # sequenceA :: Applicative f0 => IdentityT f (f0 a) -> f0 (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) #
Contravariant f => Contravariant (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods contramap :: (a -> b) -> IdentityT f b -> IdentityT f a # (>$) :: b -> IdentityT f b -> IdentityT f a #
Eq1 f => Eq1 (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods liftEq :: (a -> b -> Bool) -> IdentityT f a -> IdentityT f b -> Bool #
Ord1 f => Ord1 (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods liftCompare :: (a -> b -> Ordering) -> IdentityT f a -> IdentityT f b -> Ordering #
Read1 f => Read1 (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (IdentityT f a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [IdentityT f a] # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (IdentityT f a) # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [IdentityT f a] #
Show1 f => Show1 (IdentityT f) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods liftIO :: IO a -> IdentityT m a #
Alternative m => Alternative (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods mzero :: IdentityT m a # mplus :: IdentityT m a -> IdentityT m a -> IdentityT m a #
(Eq1 f, Eq a) => Eq (IdentityT f a) Source #
Instance details Defined in Control.Monad.Trans.Identity Methods (==) :: IdentityT f a -> IdentityT f a -> Bool # (/=) :: IdentityT f a -> IdentityT f a -> Bool #
(Ord1 f, Ord a) => Ord (IdentityT f a) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity 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) Source #
Instance details Defined in Control.Monad.Trans.Identity 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 Source #

Lift a unary operation to the new monad.

Lifting other operations

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

Lift a catchE operation to the new monad.

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

Lift a callCC operation to the new monad.