Data.Strict.Maybe

Strict Maybe.

Same as the standard Haskell Maybe, but Just _|_ = _|_

Note that strict Maybe is not a monad since return _|_ >>= f = _|_ which is not necessarily the same as f _|_.

Documentation

data Maybe a

The type of strict optional values.

Constructors

Nothing

Just !a

Instances

Functor Maybe

Methods

fmap :: (a -> b) -> Maybe a -> Maybe b

(<$) :: a -> Maybe b -> Maybe a

Foldable Maybe

Methods

fold :: Monoid m => Maybe m -> m

foldMap :: Monoid m => (a -> m) -> Maybe a -> m

foldr :: (a -> b -> b) -> b -> Maybe a -> b

foldr' :: (a -> b -> b) -> b -> Maybe a -> b

foldl :: (b -> a -> b) -> b -> Maybe a -> b

foldl' :: (b -> a -> b) -> b -> Maybe a -> b

foldr1 :: (a -> a -> a) -> Maybe a -> a

foldl1 :: (a -> a -> a) -> Maybe a -> a

toList :: Maybe a -> [a]

null :: Maybe a -> Bool

length :: Maybe a -> Int

elem :: Eq a => a -> Maybe a -> Bool

maximum :: Ord a => Maybe a -> a

minimum :: Ord a => Maybe a -> a

sum :: Num a => Maybe a -> a

product :: Num a => Maybe a -> a

Traversable Maybe

Methods

traverse :: Applicative f => (a -> f b) -> Maybe a -> f (Maybe b)

sequenceA :: Applicative f => Maybe (f a) -> f (Maybe a)

mapM :: Monad m => (a -> m b) -> Maybe a -> m (Maybe b)

sequence :: Monad m => Maybe (m a) -> m (Maybe a)

Generic1 Maybe

Associated Types

type Rep1 (Maybe :: * -> *) :: * -> *

Methods

from1 :: Maybe a -> Rep1 Maybe a

to1 :: Rep1 Maybe a -> Maybe a

Eq a => Eq (Maybe a)

Methods

(==) :: Maybe a -> Maybe a -> Bool

(/=) :: Maybe a -> Maybe a -> Bool

Data a => Data (Maybe a)

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Maybe a -> c (Maybe a)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Maybe a)

toConstr :: Maybe a -> Constr

dataTypeOf :: Maybe a -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c (Maybe a))

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Maybe a))

gmapT :: (forall b. Data b => b -> b) -> Maybe a -> Maybe a

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Maybe a -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Maybe a -> r

gmapQ :: (forall d. Data d => d -> u) -> Maybe a -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Maybe a -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Maybe a -> m (Maybe a)

Ord a => Ord (Maybe a)

Methods

compare :: Maybe a -> Maybe a -> Ordering

(<) :: Maybe a -> Maybe a -> Bool

(<=) :: Maybe a -> Maybe a -> Bool

(>) :: Maybe a -> Maybe a -> Bool

(>=) :: Maybe a -> Maybe a -> Bool

max :: Maybe a -> Maybe a -> Maybe a

min :: Maybe a -> Maybe a -> Maybe a

Read a => Read (Maybe a)

Methods

readsPrec :: Int -> ReadS (Maybe a)

readList :: ReadS [Maybe a]

readPrec :: ReadPrec (Maybe a)

readListPrec :: ReadPrec [Maybe a]

Show a => Show (Maybe a)

Methods

showsPrec :: Int -> Maybe a -> ShowS

show :: Maybe a -> String

showList :: [Maybe a] -> ShowS

Generic (Maybe a)

Associated Types

type Rep (Maybe a) :: * -> *

Methods

from :: Maybe a -> Rep (Maybe a) x

to :: Rep (Maybe a) x -> Maybe a

Semigroup a => Semigroup (Maybe a)

Methods

(<>) :: Maybe a -> Maybe a -> Maybe a

sconcat :: NonEmpty (Maybe a) -> Maybe a

stimes :: Integral b => b -> Maybe a -> Maybe a

Monoid a => Monoid (Maybe a)

Methods

mempty :: Maybe a

mappend :: Maybe a -> Maybe a -> Maybe a

mconcat :: [Maybe a] -> Maybe a

type Rep1 Maybe

type Rep1 Maybe = D1 (MetaData "Maybe" "Data.Strict.Maybe" "strict-base-0.4.0.0-1k3wDu59CS22iu6yIZo2Dn" False) ((:+:) (C1 (MetaCons "Nothing" PrefixI False) U1) (C1 (MetaCons "Just" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness SourceStrict DecidedStrict) Par1)))

type Rep (Maybe a)

type Rep (Maybe a) = D1 (MetaData "Maybe" "Data.Strict.Maybe" "strict-base-0.4.0.0-1k3wDu59CS22iu6yIZo2Dn" False) ((:+:) (C1 (MetaCons "Nothing" PrefixI False) U1) (C1 (MetaCons "Just" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness SourceStrict DecidedStrict) (Rec0 a))))

isJust :: Maybe a -> Bool

Yields True iff the argument is of the form Just _.

isNothing :: Maybe a -> Bool

Yields True iff the argument is Nothing.

fromMaybe :: a -> Maybe a -> a

Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.

maybe :: b -> (a -> b) -> Maybe a -> b

Given a default value, a function and a Maybe value, yields the default value if the Maybe value is Nothing and applies the function to the value stored in the Just otherwise.

listToMaybe :: [a] -> Maybe a

Analogous to listToMaybe in Data.Maybe.

maybeToList :: Maybe a -> [a]

Analogous to maybeToList in Data.Maybe.

mapMaybe :: (a -> Maybe b) -> [a] -> [b]

Analogous to mapMaybe in Data.Maybe.

catMaybes :: [Maybe a] -> [a]

Analogous to catMaybes in Data.Maybe.

Orphan instances

IsStrict (Maybe a) (Maybe a)

Methods

fromStrict :: Maybe a -> Maybe a

toStrict :: Maybe a -> Maybe a