strict-0.5.1: Strict data types and String IO.

Safe Haskell	Safe
Language	Haskell2010

Data.Strict.Maybe

Description

The strict variant of the standard Haskell Maybe type and the corresponding variants of the functions from Data.Maybe.

Note that in contrast to the standard lazy Maybe type, the strict Maybe type is not an applicative functor, and therefore also not a monad. The problem is the homomorphism law, which states that

pure f <*> pure x = pure (f x)  -- must hold for all f

This law does not hold for the expected applicative functor instance of Maybe, as this instance does not satisfy pure f <*> pure _|_ = pure (f _|_) for f = const.

Synopsis

data Maybe a
- = Nothing
- | Just !a
isJust :: Maybe a -> Bool
isNothing :: Maybe a -> Bool
fromJust :: Maybe a -> a
fromMaybe :: a -> Maybe a -> a
maybe :: b -> (a -> b) -> Maybe a -> b
listToMaybe :: [a] -> Maybe a
maybeToList :: Maybe a -> [a]
catMaybes :: [Maybe a] -> [a]
mapMaybe :: (a -> Maybe b) -> [a] -> [b]

Documentation

data Maybe a Source #

The type of strict optional values.

Constructors

Nothing
Just !a

Instances

Instances details

Foldable Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

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

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

Eq1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftEq :: (a -> b -> Bool) -> Maybe a -> Maybe b -> Bool #

Ord1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftCompare :: (a -> b -> Ordering) -> Maybe a -> Maybe b -> Ordering #

Read1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Maybe a) #

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Maybe a] #

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Maybe a) #

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Maybe a] #

Show1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Maybe a -> ShowS #

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Maybe a] -> ShowS #

Traversable Maybe Source #

Instance details

Defined in Data.Strict.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) #

Functor Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

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

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

NFData1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftRnf :: (a -> ()) -> Maybe a -> () #

Hashable1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Maybe a -> Int #

Generic1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

Associated Types

type Rep1 Maybe
Instance details Defined in Data.Strict.Maybe type Rep1 Maybe = D1 ('MetaData "Maybe" "Data.Strict.Maybe" "strict-0.5.1-Lw75xkawdvi6Zdi9613P2j" 'False) (C1 ('MetaCons "Nothing" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "Just" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) Par1))

Methods

from1 :: Maybe a -> Rep1 Maybe a #

to1 :: Rep1 Maybe a -> Maybe a #

Data a => Data (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

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 :: forall r r'. (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) #

Semigroup a => Monoid (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

mempty :: Maybe a #

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

mconcat :: [Maybe a] -> Maybe a #

Semigroup a => Semigroup (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

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

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

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

Generic (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Associated Types

type Rep (Maybe a)
Instance details Defined in Data.Strict.Maybe type Rep (Maybe a) = D1 ('MetaData "Maybe" "Data.Strict.Maybe" "strict-0.5.1-Lw75xkawdvi6Zdi9613P2j" 'False) (C1 ('MetaCons "Nothing" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "Just" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 a)))

Methods

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

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

Read a => Read (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

readsPrec :: Int -> ReadS (Maybe a) #

readList :: ReadS [Maybe a] #

readPrec :: ReadPrec (Maybe a) #

readListPrec :: ReadPrec [Maybe a] #

Show a => Show (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

showsPrec :: Int -> Maybe a -> ShowS #

show :: Maybe a -> String #

showList :: [Maybe a] -> ShowS #

Binary a => Binary (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

put :: Maybe a -> Put #

get :: Get (Maybe a) #

putList :: [Maybe a] -> Put #

NFData a => NFData (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

rnf :: Maybe a -> () #

Eq a => Eq (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

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

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

Ord a => Ord (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

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 #

Hashable a => Hashable (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

Methods

hashWithSalt :: Int -> Maybe a -> Int #

hash :: Maybe a -> Int #

Strict (Maybe a) (Maybe a) Source #

Instance details

Defined in Data.Strict.Classes

Methods

toStrict :: Maybe a -> Maybe a Source #

toLazy :: Maybe a -> Maybe a Source #

type Rep1 Maybe Source #

Instance details

Defined in Data.Strict.Maybe

type Rep1 Maybe = D1 ('MetaData "Maybe" "Data.Strict.Maybe" "strict-0.5.1-Lw75xkawdvi6Zdi9613P2j" 'False) (C1 ('MetaCons "Nothing" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "Just" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) Par1))

type Rep (Maybe a) Source #

Instance details

Defined in Data.Strict.Maybe

type Rep (Maybe a) = D1 ('MetaData "Maybe" "Data.Strict.Maybe" "strict-0.5.1-Lw75xkawdvi6Zdi9613P2j" 'False) (C1 ('MetaCons "Nothing" 'PrefixI 'False) (U1 :: Type -> Type) :+: C1 ('MetaCons "Just" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 a)))

isJust :: Maybe a -> Bool Source #

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

isNothing :: Maybe a -> Bool Source #

Yields True iff the argument is Nothing.

fromJust :: Maybe a -> a Source #

Extracts the element out of a Just and throws an error if the argument is Nothing.

fromMaybe :: a -> Maybe a -> a Source #

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 Source #

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 Source #

Analogous to listToMaybe in Data.Maybe.

maybeToList :: Maybe a -> [a] Source #

Analogous to maybeToList in Data.Maybe.

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

Analogous to catMaybes in Data.Maybe.

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

Analogous to mapMaybe in Data.Maybe.