planet-mitchell-0.0.0: Planet Mitchell

Safe HaskellSafe
LanguageHaskell2010

MaybeT

Contents

Synopsis

MaybeT

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

Instances
MonadTrans MaybeT 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

lift :: Monad m => m a -> MaybeT m a #

MMonad MaybeT 
Instance details

Defined in Control.Monad.Morph

Methods

embed :: Monad n => (forall a. m a -> MaybeT n a) -> MaybeT m b -> MaybeT n b #

MonadReader r m => MonadReader r (MaybeT m) 
Instance details

Defined in Control.Monad.Reader.Class

Methods

ask :: MaybeT m r #

local :: (r -> r) -> MaybeT m a -> MaybeT m a #

reader :: (r -> a) -> MaybeT m a #

MonadState s m => MonadState s (MaybeT m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: MaybeT m s #

put :: s -> MaybeT m () #

state :: (s -> (a, s)) -> MaybeT m a #

(Functor f, MonadFree f m) => MonadFree f (MaybeT m) 
Instance details

Defined in Control.Monad.Free.Class

Methods

wrap :: f (MaybeT m a) -> MaybeT m a #

MonadError e m => MonadError e (MaybeT m) 
Instance details

Defined in Control.Monad.Error.Class

Methods

throwError :: e -> MaybeT m a #

catchError :: MaybeT m a -> (e -> MaybeT m a) -> MaybeT m a #

MonadWriter w m => MonadWriter w (MaybeT m) 
Instance details

Defined in Control.Monad.Writer.Class

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 #

MonadBase b m => MonadBase b (MaybeT m) 
Instance details

Defined in Control.Monad.Base

Methods

liftBase :: b α -> MaybeT m α #

Monad m => Monad (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

fmap :: (a -> b) -> MaybeT m a -> MaybeT m b #

(<$) :: a -> MaybeT m b -> MaybeT m a #

MonadFix m => MonadFix (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

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

Monad m => MonadFail (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

fail :: String -> MaybeT m a #

(Functor m, Monad m) => Applicative (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

traverse :: Applicative f0 => (a -> f0 b) -> MaybeT f a -> f0 (MaybeT f b) #

sequenceA :: Applicative f0 => MaybeT f (f0 a) -> f0 (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) #

(Functor m, Monad m) => Alternative (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

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] #

Contravariant m => Contravariant (MaybeT m) 
Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a -> b) -> MaybeT m b -> MaybeT m a #

(>$) :: b -> MaybeT m b -> MaybeT m a #

Monad m => MonadPlus (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

mzero :: MaybeT m a #

mplus :: MaybeT m a -> MaybeT m a -> MaybeT m a #

Eq1 m => Eq1 (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

liftEq :: (a -> b -> Bool) -> MaybeT m a -> MaybeT m b -> Bool #

Ord1 m => Ord1 (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

liftCompare :: (a -> b -> Ordering) -> MaybeT m a -> MaybeT m b -> Ordering #

Read1 m => Read1 (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

liftIO :: IO a -> MaybeT m a #

MonadMask m => MonadMask (MaybeT m)

Since: exceptions-0.10.0

Instance details

Defined in Control.Monad.Catch

Methods

mask :: ((forall a. MaybeT m a -> MaybeT m a) -> MaybeT m b) -> MaybeT m b #

uninterruptibleMask :: ((forall a. MaybeT m a -> MaybeT m a) -> MaybeT m b) -> MaybeT m b #

generalBracket :: MaybeT m a -> (a -> ExitCase b -> MaybeT m c) -> (a -> MaybeT m b) -> MaybeT m (b, c) #

MonadCatch m => MonadCatch (MaybeT m)

Catches exceptions from the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

catch :: Exception e => MaybeT m a -> (e -> MaybeT m a) -> MaybeT m a #

MonadThrow m => MonadThrow (MaybeT m)

Throws exceptions into the base monad.

Instance details

Defined in Control.Monad.Catch

Methods

throwM :: Exception e => e -> MaybeT m a #

Divisible m => Divisible (MaybeT m) 
Instance details

Defined in Data.Functor.Contravariant.Divisible

Methods

divide :: (a -> (b, c)) -> MaybeT m b -> MaybeT m c -> MaybeT m a #

conquer :: MaybeT m a #

Divisible m => Decidable (MaybeT m) 
Instance details

Defined in Data.Functor.Contravariant.Divisible

Methods

lose :: (a -> Void) -> MaybeT m a #

choose :: (a -> Either b c) -> MaybeT m b -> MaybeT m c -> MaybeT m a #

PrimMonad m => PrimMonad (MaybeT m) 
Instance details

Defined in Control.Monad.Primitive

Associated Types

type PrimState (MaybeT m) :: * #

Methods

primitive :: (State# (PrimState (MaybeT m)) -> (#State# (PrimState (MaybeT m)), a#)) -> MaybeT m a #

MonadTest m => MonadTest (MaybeT m) 
Instance details

Defined in Hedgehog.Internal.Property

Methods

liftTest :: Test a -> MaybeT m a #

MonadGen m => MonadGen (MaybeT m) 
Instance details

Defined in Hedgehog.Internal.Gen

Methods

liftGen :: Gen a -> MaybeT m a #

shrinkGen :: (a -> [a]) -> MaybeT m a -> MaybeT m a #

pruneGen :: MaybeT m a -> MaybeT m a #

scaleGen :: (Size -> Size) -> MaybeT m a -> MaybeT m a #

freezeGen :: MaybeT m a -> MaybeT m (a, MaybeT m a) #

(Functor m, Monad m) => Apply (MaybeT m) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: MaybeT m (a -> b) -> MaybeT m a -> MaybeT m b #

(.>) :: MaybeT m a -> MaybeT m b -> MaybeT m b #

(<.) :: MaybeT m a -> MaybeT m b -> MaybeT m a #

liftF2 :: (a -> b -> c) -> MaybeT m a -> MaybeT m b -> MaybeT m c #

MonadManaged m => MonadManaged (MaybeT m) 
Instance details

Defined in Control.Monad.Managed

Methods

using :: Managed a -> MaybeT m a #

MonadCont m => MonadCont (MaybeT m) 
Instance details

Defined in Control.Monad.Cont.Class

Methods

callCC :: ((a -> MaybeT m b) -> MaybeT m a) -> MaybeT m a #

Pointed m => Pointed (MaybeT m) 
Instance details

Defined in Data.Pointed

Methods

point :: a -> MaybeT m a #

(Bind f, Monad f) => Plus (MaybeT f) 
Instance details

Defined in Data.Functor.Plus

Methods

zero :: MaybeT f a #

(Bind f, Monad f) => Alt (MaybeT f) 
Instance details

Defined in Data.Functor.Alt

Methods

(<!>) :: MaybeT f a -> MaybeT f a -> MaybeT f a #

some :: Applicative (MaybeT f) => MaybeT f a -> MaybeT f [a] #

many :: Applicative (MaybeT f) => MaybeT f a -> MaybeT f [a] #

(Functor m, Monad m) => Bind (MaybeT m) 
Instance details

Defined in Data.Functor.Bind.Class

Methods

(>>-) :: MaybeT m a -> (a -> MaybeT m b) -> MaybeT m b #

join :: MaybeT m (MaybeT m a) -> MaybeT m a #

MFunctor MaybeT 
Instance details

Defined in Control.Monad.Morph

Methods

hoist :: Monad m => (forall a. m a -> n a) -> MaybeT m b -> MaybeT n b #

Zoom m n s t => Zoom (MaybeT m) (MaybeT n) s t 
Instance details

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (MaybeT m) c) t s -> MaybeT m c -> MaybeT n c #

(Eq1 m, Eq a) => Eq (MaybeT m a) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

(==) :: MaybeT m a -> MaybeT m a -> Bool #

(/=) :: MaybeT m a -> MaybeT m a -> Bool #

(Ord1 m, Ord a) => Ord (MaybeT m a) 
Instance details

Defined in Control.Monad.Trans.Maybe

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) 
Instance details

Defined in Control.Monad.Trans.Maybe

(Show1 m, Show a) => Show (MaybeT m a) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

showsPrec :: Int -> MaybeT m a -> ShowS #

show :: MaybeT m a -> String #

showList :: [MaybeT m a] -> ShowS #

Wrapped (MaybeT m a) 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped (MaybeT m a) :: * #

Methods

_Wrapped' :: Iso' (MaybeT m a) (Unwrapped (MaybeT m a)) #

t ~ MaybeT n b => Rewrapped (MaybeT m a) t 
Instance details

Defined in Control.Lens.Wrapped

type Zoomed (MaybeT m) 
Instance details

Defined in Control.Lens.Zoom

type PrimState (MaybeT m) 
Instance details

Defined in Control.Monad.Primitive

type Unwrapped (MaybeT m a) 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped (MaybeT m a) = m (Maybe a)

mapMaybeT :: (m (Maybe a) -> n (Maybe b)) -> MaybeT m a -> MaybeT n b #

Transform the computation inside a MaybeT.