Data.HashMap.Lazy

A map from hashable keys to values. A map cannot contain duplicate keys; each key can map to at most one value. A HashMap makes no guarantees as to the order of its elements.

The implementation is based on hash array mapped tries. A HashMap is often faster than other tree-based set types, especially when key comparison is expensive, as in the case of strings.

Many operations have a average-case complexity of O(log n). The implementation uses a large base (i.e. 16) so in practice these operations are constant time.

Strictness properties

This module satisfies the following strictness property:

• Key arguments are evaluated to WHNF

data HashMap k v

A map from keys to values. A map cannot contain duplicate keys; each key can map to at most one value.

Instances

Eq2 HashMap

Methods

liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> HashMap a c -> HashMap b d -> Bool

Show2 HashMap

Methods

liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> HashMap a b -> ShowS

liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [HashMap a b] -> ShowS

Hashable2 HashMap

Methods

liftHashWithSalt2 :: (Int -> a -> Int) -> (Int -> b -> Int) -> Int -> HashMap a b -> Int

Functor (HashMap k)

Methods

fmap :: (a -> b) -> HashMap k a -> HashMap k b

(<$) :: a -> HashMap k b -> HashMap k a

Foldable (HashMap k)

Methods

fold :: Monoid m => HashMap k m -> m

foldMap :: Monoid m => (a -> m) -> HashMap k a -> m

foldr :: (a -> b -> b) -> b -> HashMap k a -> b

foldr' :: (a -> b -> b) -> b -> HashMap k a -> b

foldl :: (b -> a -> b) -> b -> HashMap k a -> b

foldl' :: (b -> a -> b) -> b -> HashMap k a -> b

foldr1 :: (a -> a -> a) -> HashMap k a -> a

foldl1 :: (a -> a -> a) -> HashMap k a -> a

toList :: HashMap k a -> [a]

null :: HashMap k a -> Bool

length :: HashMap k a -> Int

elem :: Eq a => a -> HashMap k a -> Bool

maximum :: Ord a => HashMap k a -> a

minimum :: Ord a => HashMap k a -> a

sum :: Num a => HashMap k a -> a

product :: Num a => HashMap k a -> a

Traversable (HashMap k)

Methods

traverse :: Applicative f => (a -> f b) -> HashMap k a -> f (HashMap k b)

sequenceA :: Applicative f => HashMap k (f a) -> f (HashMap k a)

mapM :: Monad m => (a -> m b) -> HashMap k a -> m (HashMap k b)

sequence :: Monad m => HashMap k (m a) -> m (HashMap k a)

Eq k => Eq1 (HashMap k)

Methods

liftEq :: (a -> b -> Bool) -> HashMap k a -> HashMap k b -> Bool

(Eq k, Hashable k, Read k) => Read1 (HashMap k)

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (HashMap k a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [HashMap k a]

Show k => Show1 (HashMap k)

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> HashMap k a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [HashMap k a] -> ShowS

Hashable k => Hashable1 (HashMap k)

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> HashMap k a -> Int

(Eq k, Hashable k) => IsList (HashMap k v)

Associated Types

type Item (HashMap k v) :: *

Methods

fromList :: [Item (HashMap k v)] -> HashMap k v

fromListN :: Int -> [Item (HashMap k v)] -> HashMap k v

toList :: HashMap k v -> [Item (HashMap k v)]

(Eq k, Eq v) => Eq (HashMap k v)

Methods

(==) :: HashMap k v -> HashMap k v -> Bool

(/=) :: HashMap k v -> HashMap k v -> Bool

(Data k, Data v, Eq k, Hashable k) => Data (HashMap k v)

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HashMap k v -> c (HashMap k v)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HashMap k v)

toConstr :: HashMap k v -> Constr

dataTypeOf :: HashMap k v -> DataType

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

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

gmapT :: (forall b. Data b => b -> b) -> HashMap k v -> HashMap k v

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HashMap k v -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HashMap k v -> r

gmapQ :: (forall d. Data d => d -> u) -> HashMap k v -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> HashMap k v -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> HashMap k v -> m (HashMap k v)

(Eq k, Hashable k, Read k, Read e) => Read (HashMap k e)

Methods

readsPrec :: Int -> ReadS (HashMap k e)

readList :: ReadS [HashMap k e]

readPrec :: ReadPrec (HashMap k e)

readListPrec :: ReadPrec [HashMap k e]

(Show k, Show v) => Show (HashMap k v)

Methods

showsPrec :: Int -> HashMap k v -> ShowS

show :: HashMap k v -> String

showList :: [HashMap k v] -> ShowS

(Eq k, Hashable k) => Semigroup (HashMap k v)

Methods

(<>) :: HashMap k v -> HashMap k v -> HashMap k v

sconcat :: NonEmpty (HashMap k v) -> HashMap k v

stimes :: Integral b => b -> HashMap k v -> HashMap k v

(Eq k, Hashable k) => Monoid (HashMap k v)

Methods

mempty :: HashMap k v

mappend :: HashMap k v -> HashMap k v -> HashMap k v

mconcat :: [HashMap k v] -> HashMap k v

(NFData k, NFData v) => NFData (HashMap k v)

Methods

rnf :: HashMap k v -> ()

(Hashable k, Hashable v) => Hashable (HashMap k v)

Methods

hashWithSalt :: Int -> HashMap k v -> Int

hash :: HashMap k v -> Int

type Item (HashMap k v)

type Item (HashMap k v) = (k, v)

Construction

empty :: HashMap k v

O(1) Construct an empty map.

singleton :: Hashable k => k -> v -> HashMap k v

O(1) Construct a map with a single element.

Basic interface

null :: HashMap k v -> Bool

O(1) Return True if this map is empty, False otherwise.

size :: HashMap k v -> Int

O(n) Return the number of key-value mappings in this map.

member :: (Eq k, Hashable k) => k -> HashMap k a -> Bool

O(log n) Return True if the specified key is present in the map, False otherwise.

lookup :: (Eq k, Hashable k) => k -> HashMap k v -> Maybe v

O(log n) Return the value to which the specified key is mapped, or Nothing if this map contains no mapping for the key.

lookupDefault

Arguments

:: (Eq k, Hashable k)

=> v

Default value to return.

-> k

-> HashMap k v

-> v

O(log n) Return the value to which the specified key is mapped, or the default value if this map contains no mapping for the key.

(!) :: (Eq k, Hashable k) => HashMap k v -> k -> v infixl 9

O(log n) Return the value to which the specified key is mapped. Calls error if this map contains no mapping for the key.

insert :: (Eq k, Hashable k) => k -> v -> HashMap k v -> HashMap k v

O(log n) Associate the specified value with the specified key in this map. If this map previously contained a mapping for the key, the old value is replaced.

insertWith :: (Eq k, Hashable k) => (v -> v -> v) -> k -> v -> HashMap k v -> HashMap k v

O(log n) Associate the value with the key in this map. If this map previously contained a mapping for the key, the old value is replaced by the result of applying the given function to the new and old value. Example:

insertWith f k v map
  where f new old = new + old

delete :: (Eq k, Hashable k) => k -> HashMap k v -> HashMap k v

O(log n) Remove the mapping for the specified key from this map if present.

adjust :: (Eq k, Hashable k) => (v -> v) -> k -> HashMap k v -> HashMap k v

O(log n) Adjust the value tied to a given key in this map only if it is present. Otherwise, leave the map alone.

update :: (Eq k, Hashable k) => (a -> Maybe a) -> k -> HashMap k a -> HashMap k a

O(log n) The expression (update f k map) updates the value x at k, (if it is in the map). If (f k x) is Nothing, the element is deleted. If it is (Just y), the key k is bound to the new value y.

alter :: (Eq k, Hashable k) => (Maybe v -> Maybe v) -> k -> HashMap k v -> HashMap k v

O(log n) The expression (alter f k map) alters the value x at k, or absence thereof. alter can be used to insert, delete, or update a value in a map. In short : lookup k (alter f k m) = f (lookup k m).

Combine

Union

union :: (Eq k, Hashable k) => HashMap k v -> HashMap k v -> HashMap k v

O(n+m) The union of two maps. If a key occurs in both maps, the mapping from the first will be the mapping in the result.

unionWith :: (Eq k, Hashable k) => (v -> v -> v) -> HashMap k v -> HashMap k v -> HashMap k v

O(n+m) The union of two maps. If a key occurs in both maps, the provided function (first argument) will be used to compute the result.

unionWithKey :: (Eq k, Hashable k) => (k -> v -> v -> v) -> HashMap k v -> HashMap k v -> HashMap k v

O(n+m) The union of two maps. If a key occurs in both maps, the provided function (first argument) will be used to compute the result.

unions :: (Eq k, Hashable k) => [HashMap k v] -> HashMap k v

Construct a set containing all elements from a list of sets.

Transformations

map :: (v1 -> v2) -> HashMap k v1 -> HashMap k v2

O(n) Transform this map by applying a function to every value.

mapWithKey :: (k -> v1 -> v2) -> HashMap k v1 -> HashMap k v2

O(n) Transform this map by applying a function to every value.

traverseWithKey :: Applicative f => (k -> v1 -> f v2) -> HashMap k v1 -> f (HashMap k v2)

O(n) Transform this map by accumulating an Applicative result from every value.

Difference and intersection

difference :: (Eq k, Hashable k) => HashMap k v -> HashMap k w -> HashMap k v

O(n*log m) Difference of two maps. Return elements of the first map not existing in the second.

differenceWith :: (Eq k, Hashable k) => (v -> w -> Maybe v) -> HashMap k v -> HashMap k w -> HashMap k v

O(n*log m) Difference with a combining function. When two equal keys are encountered, the combining function is applied to the values of these keys. If it returns Nothing, the element is discarded (proper set difference). If it returns (Just y), the element is updated with a new value y.

intersection :: (Eq k, Hashable k) => HashMap k v -> HashMap k w -> HashMap k v

O(n*log m) Intersection of two maps. Return elements of the first map for keys existing in the second.

intersectionWith :: (Eq k, Hashable k) => (v1 -> v2 -> v3) -> HashMap k v1 -> HashMap k v2 -> HashMap k v3

O(n+m) Intersection of two maps. If a key occurs in both maps the provided function is used to combine the values from the two maps.

intersectionWithKey :: (Eq k, Hashable k) => (k -> v1 -> v2 -> v3) -> HashMap k v1 -> HashMap k v2 -> HashMap k v3

O(n+m) Intersection of two maps. If a key occurs in both maps the provided function is used to combine the values from the two maps.

Folds

foldl' :: (a -> v -> a) -> a -> HashMap k v -> a

O(n) Reduce this map by applying a binary operator to all elements, using the given starting value (typically the left-identity of the operator). Each application of the operator is evaluated before before using the result in the next application. This function is strict in the starting value.

foldlWithKey' :: (a -> k -> v -> a) -> a -> HashMap k v -> a

O(n) Reduce this map by applying a binary operator to all elements, using the given starting value (typically the left-identity of the operator). Each application of the operator is evaluated before before using the result in the next application. This function is strict in the starting value.

foldr :: (v -> a -> a) -> a -> HashMap k v -> a

O(n) Reduce this map by applying a binary operator to all elements, using the given starting value (typically the right-identity of the operator).

foldrWithKey :: (k -> v -> a -> a) -> a -> HashMap k v -> a

O(n) Reduce this map by applying a binary operator to all elements, using the given starting value (typically the right-identity of the operator).

Filter

filter :: (v -> Bool) -> HashMap k v -> HashMap k v

O(n) Filter this map by retaining only elements which values satisfy a predicate.

filterWithKey :: forall k v. (k -> v -> Bool) -> HashMap k v -> HashMap k v

O(n) Filter this map by retaining only elements satisfying a predicate.

mapMaybe :: (v1 -> Maybe v2) -> HashMap k v1 -> HashMap k v2

O(n) Transform this map by applying a function to every value and retaining only some of them.

mapMaybeWithKey :: (k -> v1 -> Maybe v2) -> HashMap k v1 -> HashMap k v2

O(n) Transform this map by applying a function to every value and retaining only some of them.

Conversions

keys :: HashMap k v -> [k]

O(n) Return a list of this map's keys. The list is produced lazily.

elems :: HashMap k v -> [v]

O(n) Return a list of this map's values. The list is produced lazily.

Lists

toList :: HashMap k v -> [(k, v)]

O(n) Return a list of this map's elements. The list is produced lazily. The order of its elements is unspecified.

fromList :: (Eq k, Hashable k) => [(k, v)] -> HashMap k v

O(n) Construct a map with the supplied mappings. If the list contains duplicate mappings, the later mappings take precedence.

fromListWith :: (Eq k, Hashable k) => (v -> v -> v) -> [(k, v)] -> HashMap k v

O(n*log n) Construct a map from a list of elements. Uses the provided function to merge duplicate entries.