{-# LANGUAGE CPP, DeriveDataTypeable #-} ------------------------------------------------------------------------ -- | -- Module : Data.HashSet -- Copyright : 2011 Bryan O'Sullivan -- License : BSD-style -- Maintainer : johan.tibell@gmail.com -- Stability : provisional -- Portability : portable -- -- A set of /hashable/ values. A set cannot contain duplicate items. -- A 'HashSet' makes no guarantees as to the order of its elements. -- -- The implementation is based on /hash array mapped trie/. A -- 'HashSet' is often faster than other tree-based set types, -- especially when value 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. module Data.HashSet ( HashSet -- * Construction , empty , singleton -- * Combine , union , unions -- * Basic interface , null , size , member , insert , delete -- * Transformations , map -- * Difference and intersection , difference , intersection -- * Folds , foldl' , foldr -- * Filter , filter -- ** Lists , toList , fromList ) where import Control.DeepSeq (NFData(..)) import Data.Data hiding (Typeable) import Data.HashMap.Base (HashMap, foldrWithKey) import Data.Hashable (Hashable) import Data.Monoid (Monoid(..)) import GHC.Exts (build) import Prelude hiding (filter, foldr, map, null) import qualified Data.Foldable as Foldable import qualified Data.HashMap.Lazy as H import qualified Data.List as List import Data.Typeable (Typeable) -- | A set of values. A set cannot contain duplicate values. newtype HashSet a = HashSet { asMap :: HashMap a () } deriving (Typeable) instance (NFData a) => NFData (HashSet a) where rnf = rnf . asMap {-# INLINE rnf #-} instance (Hashable a, Eq a) => Eq (HashSet a) where -- This performs two passes over the tree. a == b = foldr f True b && size a == size b where f i = (&& i `member` a) {-# INLINE (==) #-} instance Foldable.Foldable HashSet where foldr = Data.HashSet.foldr {-# INLINE foldr #-} instance (Hashable a, Eq a) => Monoid (HashSet a) where mempty = empty {-# INLINE mempty #-} mappend = union {-# INLINE mappend #-} instance (Show a) => Show (HashSet a) where showsPrec d m = showParen (d > 10) $ showString "fromList " . shows (toList m) instance (Data a, Eq a, Hashable a) => Data (HashSet a) where gfoldl f z m = z fromList `f` toList m toConstr _ = fromListConstr gunfold k z c = case constrIndex c of 1 -> k (z fromList) _ -> error "gunfold" dataTypeOf _ = hashSetDataType dataCast1 f = gcast1 f fromListConstr :: Constr fromListConstr = mkConstr hashSetDataType "fromList" [] Prefix hashSetDataType :: DataType hashSetDataType = mkDataType "Data.HashSet" [fromListConstr] -- | /O(1)/ Construct an empty set. empty :: HashSet a empty = HashSet H.empty -- | /O(1)/ Construct a set with a single element. singleton :: Hashable a => a -> HashSet a singleton a = HashSet (H.singleton a ()) {-# INLINABLE singleton #-} -- | /O(n+m)/ Construct a set containing all elements from both sets. -- -- To obtain good performance, the smaller set must be presented as -- the first argument. union :: (Eq a, Hashable a) => HashSet a -> HashSet a -> HashSet a union s1 s2 = HashSet $ H.union (asMap s1) (asMap s2) {-# INLINE union #-} -- TODO: Figure out the time complexity of 'unions'. -- | Construct a set containing all elements from a list of sets. unions :: (Eq a, Hashable a) => [HashSet a] -> HashSet a unions = List.foldl' union empty {-# INLINE unions #-} -- | /O(1)/ Return 'True' if this set is empty, 'False' otherwise. null :: HashSet a -> Bool null = H.null . asMap {-# INLINE null #-} -- | /O(n)/ Return the number of elements in this set. size :: HashSet a -> Int size = H.size . asMap {-# INLINE size #-} -- | /O(min(n,W))/ Return 'True' if the given value is present in this -- set, 'False' otherwise. member :: (Eq a, Hashable a) => a -> HashSet a -> Bool member a s = case H.lookup a (asMap s) of Just _ -> True _ -> False {-# INLINABLE member #-} -- | /O(min(n,W))/ Add the specified value to this set. insert :: (Eq a, Hashable a) => a -> HashSet a -> HashSet a insert a = HashSet . H.insert a () . asMap {-# INLINABLE insert #-} -- | /O(min(n,W))/ Remove the specified value from this set if -- present. delete :: (Eq a, Hashable a) => a -> HashSet a -> HashSet a delete a = HashSet . H.delete a . asMap {-# INLINABLE delete #-} -- | /O(n)/ Transform this set by applying a function to every value. -- The resulting set may be smaller than the source. map :: (Hashable b, Eq b) => (a -> b) -> HashSet a -> HashSet b map f = fromList . List.map f . toList {-# INLINE map #-} -- | /O(n)/ Difference of two sets. Return elements of the first set -- not existing in the second. difference :: (Eq a, Hashable a) => HashSet a -> HashSet a -> HashSet a difference (HashSet a) (HashSet b) = HashSet (H.difference a b) {-# INLINABLE difference #-} -- | /O(n)/ Intersection of two sets. Return elements present in both -- the first set and the second. intersection :: (Eq a, Hashable a) => HashSet a -> HashSet a -> HashSet a intersection (HashSet a) (HashSet b) = HashSet (H.intersection a b) {-# INLINABLE intersection #-} -- | /O(n)/ Reduce this set 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. foldl' :: (a -> b -> a) -> a -> HashSet b -> a foldl' f z0 = H.foldlWithKey' g z0 . asMap where g z k _ = f z k {-# INLINE foldl' #-} -- | /O(n)/ Reduce this set by applying a binary operator to all -- elements, using the given starting value (typically the -- right-identity of the operator). foldr :: (b -> a -> a) -> a -> HashSet b -> a foldr f z0 = foldrWithKey g z0 . asMap where g k _ z = f k z {-# INLINE foldr #-} -- | /O(n)/ Filter this set by retaining only elements satisfying a -- predicate. filter :: (a -> Bool) -> HashSet a -> HashSet a filter p = HashSet . H.filterWithKey q . asMap where q k _ = p k {-# INLINE filter #-} -- | /O(n)/ Return a list of this set's elements. The list is -- produced lazily. toList :: HashSet a -> [a] toList t = build (\ c z -> foldrWithKey ((const .) c) z (asMap t)) {-# INLINE toList #-} -- | /O(n*min(W, n))/ Construct a set from a list of elements. fromList :: (Eq a, Hashable a) => [a] -> HashSet a fromList = HashSet . List.foldl' (\ m k -> H.insert k () m) H.empty {-# INLINE fromList #-}