Safe Haskell	Safe
Language	Haskell2010

Language.Haskell.Tools.Refactor.Utils.Maybe

Synopsis

Documentation

liftMaybe :: Monad m => Maybe a -> MaybeT m a Source #

maybeT :: Monad m => b -> (a -> b) -> MaybeT m a -> m b Source #

maybeTM :: Monad m => m b -> (a -> m b) -> MaybeT m a -> m b Source #

module Data.Maybe

newtype MaybeT (m :: * -> *) a :: (* -> *) -> * -> * #

The parameterizable maybe monad, obtained by composing an arbitrary monad with the Maybe monad.

Computations are actions that may produce a value or exit.

The return function yields a computation that produces that value, while >>= sequences two subcomputations, exiting if either computation does.

Constructors

MaybeT
Fields runMaybeT :: m (Maybe a)

Instances

MonadTrans MaybeT
Methods lift :: Monad m => m a -> MaybeT m a #
MonadWriter w m => MonadWriter w (MaybeT m)
Methods writer :: (a, w) -> MaybeT m a # tell :: w -> MaybeT m () # listen :: MaybeT m a -> MaybeT m (a, w) # pass :: MaybeT m (a, w -> w) -> MaybeT m a #
MonadState s m => MonadState s (MaybeT m)
Methods get :: MaybeT m s # put :: s -> MaybeT m () # state :: (s -> (a, s)) -> MaybeT m a #
MonadReader r m => MonadReader r (MaybeT m)
Methods ask :: MaybeT m r # local :: (r -> r) -> MaybeT m a -> MaybeT m a # reader :: (r -> a) -> MaybeT m a #
Monad m => MorphControl m (MaybeT m)
Associated Types data MSt (m :: * -> ) (MaybeT m :: -> ) a :: # Methods sink :: MaybeT m a -> m (MSt m (MaybeT m) a) # pullBack :: m (MSt m (MaybeT m) a) -> MaybeT m a #
Monad m => Monad (MaybeT m)
Methods (>>=) :: MaybeT m a -> (a -> MaybeT m b) -> MaybeT m b # (>>) :: MaybeT m a -> MaybeT m b -> MaybeT m b # return :: a -> MaybeT m a # fail :: String -> MaybeT m a #
Functor m => Functor (MaybeT m)
Methods fmap :: (a -> b) -> MaybeT m a -> MaybeT m b # (<$) :: a -> MaybeT m b -> MaybeT m a #
MonadFix m => MonadFix (MaybeT m)
Methods mfix :: (a -> MaybeT m a) -> MaybeT m a #
Monad m => MonadFail (MaybeT m)
Methods fail :: String -> MaybeT m a #
(Functor m, Monad m) => Applicative (MaybeT m)
Methods pure :: a -> MaybeT m a # (<>) :: MaybeT m (a -> b) -> MaybeT m a -> MaybeT m b # liftA2 :: (a -> b -> c) -> MaybeT m a -> MaybeT m b -> MaybeT m c # (>) :: MaybeT m a -> MaybeT m b -> MaybeT m b # (<*) :: MaybeT m a -> MaybeT m b -> MaybeT m a #
Foldable f => Foldable (MaybeT f)
Methods fold :: Monoid m => MaybeT f m -> m # foldMap :: Monoid m => (a -> m) -> MaybeT f a -> m # foldr :: (a -> b -> b) -> b -> MaybeT f a -> b # foldr' :: (a -> b -> b) -> b -> MaybeT f a -> b # foldl :: (b -> a -> b) -> b -> MaybeT f a -> b # foldl' :: (b -> a -> b) -> b -> MaybeT f a -> b # foldr1 :: (a -> a -> a) -> MaybeT f a -> a # foldl1 :: (a -> a -> a) -> MaybeT f a -> a # toList :: MaybeT f a -> [a] # null :: MaybeT f a -> Bool # length :: MaybeT f a -> Int # elem :: Eq a => a -> MaybeT f a -> Bool # maximum :: Ord a => MaybeT f a -> a # minimum :: Ord a => MaybeT f a -> a # sum :: Num a => MaybeT f a -> a # product :: Num a => MaybeT f a -> a #
Traversable f => Traversable (MaybeT f)
Methods traverse :: Applicative f => (a -> f b) -> MaybeT f a -> f (MaybeT f b) # sequenceA :: Applicative f => MaybeT f (f a) -> f (MaybeT f a) # mapM :: Monad m => (a -> m b) -> MaybeT f a -> m (MaybeT f b) # sequence :: Monad m => MaybeT f (m a) -> m (MaybeT f a) #
Monad m => MonadPlus (MaybeT m)
Methods mzero :: MaybeT m a # mplus :: MaybeT m a -> MaybeT m a -> MaybeT m a #
(Functor m, Monad m) => Alternative (MaybeT m)
Methods empty :: MaybeT m a # (<\|>) :: MaybeT m a -> MaybeT m a -> MaybeT m a # some :: MaybeT m a -> MaybeT m [a] # many :: MaybeT m a -> MaybeT m [a] #
Eq1 m => Eq1 (MaybeT m)
Methods liftEq :: (a -> b -> Bool) -> MaybeT m a -> MaybeT m b -> Bool #
Ord1 m => Ord1 (MaybeT m)
Methods liftCompare :: (a -> b -> Ordering) -> MaybeT m a -> MaybeT m b -> Ordering #
Read1 m => Read1 (MaybeT m)
Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (MaybeT m a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [MaybeT m a] # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (MaybeT m a) # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [MaybeT m a] #
Show1 m => Show1 (MaybeT m)
Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> MaybeT m a -> ShowS # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [MaybeT m a] -> ShowS #
MonadZip m => MonadZip (MaybeT m)
Methods mzip :: MaybeT m a -> MaybeT m b -> MaybeT m (a, b) # mzipWith :: (a -> b -> c) -> MaybeT m a -> MaybeT m b -> MaybeT m c # munzip :: MaybeT m (a, b) -> (MaybeT m a, MaybeT m b) #
MonadIO m => MonadIO (MaybeT m)
Methods liftIO :: IO a -> MaybeT m a #
(Monad m, HasDynFlags m) => HasDynFlags (MaybeT m)
Methods getDynFlags :: MaybeT m DynFlags #
PrimMonad m => PrimMonad (MaybeT m)
Associated Types type PrimState (MaybeT m :: * -> ) :: # Methods primitive :: (State# (PrimState (MaybeT m)) -> (#TupleRep [RuntimeRep], LiftedRep, State# (PrimState (MaybeT m)), a#)) -> MaybeT m a #
(Eq1 m, Eq a) => Eq (MaybeT m a)
Methods (==) :: MaybeT m a -> MaybeT m a -> Bool # (/=) :: MaybeT m a -> MaybeT m a -> Bool #
(Ord1 m, Ord a) => Ord (MaybeT m a)
Methods compare :: MaybeT m a -> MaybeT m a -> Ordering # (<) :: MaybeT m a -> MaybeT m a -> Bool # (<=) :: MaybeT m a -> MaybeT m a -> Bool # (>) :: MaybeT m a -> MaybeT m a -> Bool # (>=) :: MaybeT m a -> MaybeT m a -> Bool # max :: MaybeT m a -> MaybeT m a -> MaybeT m a # min :: MaybeT m a -> MaybeT m a -> MaybeT m a #
(Read1 m, Read a) => Read (MaybeT m a)
Methods readsPrec :: Int -> ReadS (MaybeT m a) # readList :: ReadS [MaybeT m a] # readPrec :: ReadPrec (MaybeT m a) # readListPrec :: ReadPrec [MaybeT m a] #
(Show1 m, Show a) => Show (MaybeT m a)
Methods showsPrec :: Int -> MaybeT m a -> ShowS # show :: MaybeT m a -> String # showList :: [MaybeT m a] -> ShowS #
data MSt m (MaybeT m)
data MSt m (MaybeT m) = MaybeMSt { fromMaybeMSt :: Maybe a }
type PrimState (MaybeT m)
type PrimState (MaybeT m) = PrimState m