--
-- An efficient implementation of integer sets.
--
--- This module is intended to be imported @qualified@, to avoid name
--- clashes with "Prelude" functions. eg.
+-- Since many function names (but not the type name) clash with
+-- "Prelude" names, this module is usually imported @qualified@, e.g.
--
--- > import Data.IntSet as Set
+-- > import Data.IntSet (IntSet)
+-- > import qualified Data.IntSet as IntSet
--
-- The implementation is based on /big-endian patricia trees/. This data
-- structure performs especially well on binary operations like 'union'
, null
, size
, member
+ , notMember
, isSubsetOf
, isProperSubsetOf
, split
, splitMember
+ -- * Min\/Max
+ , findMin
+ , findMax
+ , deleteMin
+ , deleteMax
+ , deleteFindMin
+ , deleteFindMax
+ , maxView
+ , minView
+
-- * Map
, map
import Prelude hiding (lookup,filter,foldr,foldl,null,map)
import Data.Bits
-import Data.Int
import qualified Data.List as List
import Data.Monoid (Monoid(..))
#if __GLASGOW_HASKELL__
import Text.Read
-import Data.Generics.Basics
-import Data.Generics.Instances
+import Data.Generics.Basics (Data(..), mkNorepType)
+import Data.Generics.Instances ()
#endif
#if __GLASGOW_HASKELL__ >= 503
-import GHC.Word
import GHC.Exts ( Word(..), Int(..), shiftRL# )
#elif __GLASGOW_HASKELL__
import Word
data IntSet = Nil
| Tip {-# UNPACK #-} !Int
| Bin {-# UNPACK #-} !Prefix {-# UNPACK #-} !Mask !IntSet !IntSet
+-- Invariant: Nil is never found as a child of Bin.
+
type Prefix = Int
type Mask = Int
Tip y -> (x==y)
Nil -> False
+-- | /O(min(n,W))/. Is the element not in the set?
+notMember :: Int -> IntSet -> Bool
+notMember k = not . member k
+
-- 'lookup' is used by 'intersection' for left-biasing
lookup :: Int -> IntSet -> Maybe Int
lookup k t
Nil -> (Nil,Nil)
--- | /O(log n)/. The expression (@'split' x set@) is a pair @(set1,set2)@
+-- | /O(min(n,W))/. The expression (@'split' x set@) is a pair @(set1,set2)@
-- where all elements in @set1@ are lower than @x@ and all elements in
-- @set2@ larger than @x@.
--
split x t
= case t of
Bin p m l r
- | zero x m -> let (lt,gt) = split x l in (lt,union gt r)
- | otherwise -> let (lt,gt) = split x r in (union l lt,gt)
+ | m < 0 -> if x >= 0 then let (lt,gt) = split' x l in (union r lt, gt)
+ else let (lt,gt) = split' x r in (lt, union gt l)
+ -- handle negative numbers.
+ | otherwise -> split' x t
+ Tip y
+ | x>y -> (t,Nil)
+ | x<y -> (Nil,t)
+ | otherwise -> (Nil,Nil)
+ Nil -> (Nil, Nil)
+
+split' :: Int -> IntSet -> (IntSet,IntSet)
+split' x t
+ = case t of
+ Bin p m l r
+ | match x p m -> if zero x m then let (lt,gt) = split' x l in (lt,union gt r)
+ else let (lt,gt) = split' x r in (union l lt,gt)
+ | otherwise -> if x < p then (Nil, t)
+ else (t, Nil)
Tip y
| x>y -> (t,Nil)
| x<y -> (Nil,t)
| otherwise -> (Nil,Nil)
Nil -> (Nil,Nil)
--- | /O(log n)/. Performs a 'split' but also returns whether the pivot
+-- | /O(min(n,W))/. Performs a 'split' but also returns whether the pivot
-- element was found in the original set.
splitMember :: Int -> IntSet -> (IntSet,Bool,IntSet)
splitMember x t
= case t of
Bin p m l r
- | zero x m -> let (lt,found,gt) = splitMember x l in (lt,found,union gt r)
- | otherwise -> let (lt,found,gt) = splitMember x r in (union l lt,found,gt)
+ | m < 0 -> if x >= 0 then let (lt,found,gt) = splitMember' x l in (union r lt, found, gt)
+ else let (lt,found,gt) = splitMember' x r in (lt, found, union gt l)
+ -- handle negative numbers.
+ | otherwise -> splitMember' x t
+ Tip y
+ | x>y -> (t,False,Nil)
+ | x<y -> (Nil,False,t)
+ | otherwise -> (Nil,True,Nil)
+ Nil -> (Nil,False,Nil)
+
+splitMember' :: Int -> IntSet -> (IntSet,Bool,IntSet)
+splitMember' x t
+ = case t of
+ Bin p m l r
+ | match x p m -> if zero x m then let (lt,found,gt) = splitMember x l in (lt,found,union gt r)
+ else let (lt,found,gt) = splitMember x r in (union l lt,found,gt)
+ | otherwise -> if x < p then (Nil, False, t)
+ else (t, False, Nil)
Tip y
| x>y -> (t,False,Nil)
| x<y -> (Nil,False,t)
Nil -> (Nil,False,Nil)
{----------------------------------------------------------------------
+ Min/Max
+----------------------------------------------------------------------}
+
+-- | /O(min(n,W))/. Retrieves the maximal key of the set, and the set stripped from that element
+-- @fail@s (in the monad) when passed an empty set.
+maxView :: (Monad m) => IntSet -> m (Int, IntSet)
+maxView t
+ = case t of
+ Bin p m l r | m < 0 -> let (result,t') = maxViewUnsigned l in return (result, bin p m t' r)
+ Bin p m l r -> let (result,t') = maxViewUnsigned r in return (result, bin p m l t')
+ Tip y -> return (y,Nil)
+ Nil -> fail "maxView: empty set has no maximal element"
+
+maxViewUnsigned :: IntSet -> (Int, IntSet)
+maxViewUnsigned t
+ = case t of
+ Bin p m l r -> let (result,t') = maxViewUnsigned r in (result, bin p m l t')
+ Tip y -> (y, Nil)
+
+-- | /O(min(n,W))/. Retrieves the minimal key of the set, and the set stripped from that element
+-- @fail@s (in the monad) when passed an empty set.
+minView :: (Monad m) => IntSet -> m (Int, IntSet)
+minView t
+ = case t of
+ Bin p m l r | m < 0 -> let (result,t') = minViewUnsigned r in return (result, bin p m l t')
+ Bin p m l r -> let (result,t') = minViewUnsigned l in return (result, bin p m t' r)
+ Tip y -> return (y, Nil)
+ Nil -> fail "minView: empty set has no minimal element"
+
+minViewUnsigned :: IntSet -> (Int, IntSet)
+minViewUnsigned t
+ = case t of
+ Bin p m l r -> let (result,t') = minViewUnsigned l in (result, bin p m t' r)
+ Tip y -> (y, Nil)
+
+
+-- Duplicate the Identity monad here because base < mtl.
+newtype Identity a = Identity { runIdentity :: a }
+instance Monad Identity where
+ return a = Identity a
+ m >>= k = k (runIdentity m)
+
+
+-- | /O(min(n,W))/. Delete and find the minimal element.
+--
+-- > deleteFindMin set = (findMin set, deleteMin set)
+deleteFindMin :: IntSet -> (Int, IntSet)
+deleteFindMin = runIdentity . minView
+
+-- | /O(min(n,W))/. Delete and find the maximal element.
+--
+-- > deleteFindMax set = (findMax set, deleteMax set)
+deleteFindMax :: IntSet -> (Int, IntSet)
+deleteFindMax = runIdentity . maxView
+
+-- | /O(min(n,W))/. The minimal element of a set.
+findMin :: IntSet -> Int
+findMin = fst . runIdentity . minView
+
+-- | /O(min(n,W))/. The maximal element of a set.
+findMax :: IntSet -> Int
+findMax = fst . runIdentity . maxView
+
+-- | /O(min(n,W))/. Delete the minimal element.
+deleteMin :: IntSet -> IntSet
+deleteMin = snd . runIdentity . minView
+
+-- | /O(min(n,W))/. Delete the maximal element.
+deleteMax :: IntSet -> IntSet
+deleteMax = snd . runIdentity . maxView
+
+
+
+{----------------------------------------------------------------------
Map
----------------------------------------------------------------------}
-- > elems set == fold (:) [] set
fold :: (Int -> b -> b) -> b -> IntSet -> b
fold f z t
- = foldr f z t
+ = case t of
+ Bin 0 m l r | m < 0 -> foldr f (foldr f z l) r
+ -- put negative numbers before.
+ Bin p m l r -> foldr f z t
+ Tip x -> f x z
+ Nil -> z
foldr :: (Int -> b -> b) -> b -> IntSet -> b
foldr f z t
-- | /O(n)/. Convert the set to an ascending list of elements.
toAscList :: IntSet -> [Int]
-toAscList t
- = -- NOTE: the following algorithm only works for big-endian trees
- let (pos,neg) = span (>=0) (foldr (:) [] t) in neg ++ pos
+toAscList t = toList t
-- | /O(n*min(n,W))/. Create a set from a list of integers.
fromList :: [Int] -> IntSet
projects / haskell-directory.git / blobdiff