| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Maybes
Contents
Synopsis
- data MaybeErr err val
- failME :: err -> MaybeErr err val
- isSuccess :: MaybeErr err val -> Bool
- orElse :: Maybe a -> a -> a
- firstJust :: Maybe a -> Maybe a -> Maybe a
- firstJusts :: [Maybe a] -> Maybe a
- whenIsJust :: Monad m => Maybe a -> (a -> m ()) -> m ()
- expectJust :: HasCallStack => String -> Maybe a -> a
- rightToMaybe :: Either a b -> Maybe b
- newtype MaybeT (m :: Type -> Type) a = MaybeT {}
- liftMaybeT :: Monad m => m a -> MaybeT m a
- tryMaybeT :: IO a -> MaybeT IO a
Documentation
data MaybeErr err val Source #
Instances
| Monad (MaybeErr err) Source # | |
| Functor (MaybeErr err) Source # | |
| Applicative (MaybeErr err) Source # | |
firstJusts :: [Maybe a] -> Maybe a Source #
Takes a list of Maybes and returns the first Just if there is one, or
Nothing otherwise.
whenIsJust :: Monad m => Maybe a -> (a -> m ()) -> m () Source #
expectJust :: HasCallStack => String -> Maybe a -> a Source #
rightToMaybe :: Either a b -> Maybe b Source #
MaybeT
newtype MaybeT (m :: Type -> Type) a #
Instances
| MonadTrans MaybeT | |
Defined in Control.Monad.Trans.Maybe | |
| Monad m => Monad (MaybeT m) | |
| Functor m => Functor (MaybeT m) | |
| MonadFix m => MonadFix (MaybeT m) | |
Defined in Control.Monad.Trans.Maybe | |
| Monad m => MonadFail (MaybeT m) | |
Defined in Control.Monad.Trans.Maybe | |
| (Functor m, Monad m) => Applicative (MaybeT m) | |
| Foldable f => Foldable (MaybeT f) | |
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 # elem :: Eq a => a -> MaybeT f a -> Bool # maximum :: Ord a => MaybeT f a -> a # minimum :: Ord a => MaybeT f a -> a # | |
| Traversable f => Traversable (MaybeT f) | |
Defined in Control.Monad.Trans.Maybe | |
| (Functor m, Monad m) => Alternative (MaybeT m) | |
| Monad m => MonadPlus (MaybeT m) | |
| Eq1 m => Eq1 (MaybeT m) | |
| Ord1 m => Ord1 (MaybeT m) | |
Defined in Control.Monad.Trans.Maybe Methods liftCompare :: (a -> b -> Ordering) -> MaybeT m a -> MaybeT m b -> Ordering | |
| Read1 m => Read1 (MaybeT m) | |
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) | |
Defined in Control.Monad.Trans.Maybe | |
| MonadZip m => MonadZip (MaybeT m) | |
| MonadIO m => MonadIO (MaybeT m) | |
Defined in Control.Monad.Trans.Maybe | |
| Contravariant m => Contravariant (MaybeT m) | |
| (Monad m, HasDynFlags m) => HasDynFlags (MaybeT m) Source # | |
| (Eq1 m, Eq a) => Eq (MaybeT m a) | |
| (Ord1 m, Ord a) => Ord (MaybeT m a) | |
Defined in Control.Monad.Trans.Maybe | |
| (Read1 m, Read a) => Read (MaybeT m a) | |
| (Show1 m, Show a) => Show (MaybeT m a) | |
liftMaybeT :: Monad m => m a -> MaybeT m a Source #