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

IdentityT :: (* -> *) -> * -> *) Source #

Instance details

Methods

lift :: Monad m => m a -> IdentityT m a Source #

Monad m => Monad (IdentityT m) Source #

Instance details

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

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

Methods

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

MonadFail m => MonadFail (IdentityT m) Source #

Instance details

Methods

fail :: String -> IdentityT m a #

Applicative m => Applicative (IdentityT m) Source #

Instance details

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

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

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) #

Eq1 f => Eq1 (IdentityT f) Source #

Instance details

Methods

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

Ord1 f => Ord1 (IdentityT f) Source #

Instance details

Methods

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

Read1 f => Read1 (IdentityT f) Source #

Instance details

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

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

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

Methods

liftIO :: IO a -> IdentityT m a #

Alternative m => Alternative (IdentityT m) Source #

Instance details

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

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

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

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

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

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.