1 {-# OPTIONS -cpp -fglasgow-exts #-}
2 -----------------------------------------------------------------------------
4 -- Module : Data.IntSet
5 -- Copyright : (c) Daan Leijen 2002
7 -- Maintainer : libraries@haskell.org
8 -- Stability : provisional
9 -- Portability : portable
11 -- An efficient implementation of integer sets.
13 -- This module is intended to be imported @qualified@, to avoid name
14 -- clashes with "Prelude" functions. eg.
16 -- > import Data.IntSet as Set
18 -- The implementation is based on /big-endian patricia trees/. This data
19 -- structure performs especially well on binary operations like 'union'
20 -- and 'intersection'. However, my benchmarks show that it is also
21 -- (much) faster on insertions and deletions when compared to a generic
22 -- size-balanced set implementation (see "Data.Set").
24 -- * Chris Okasaki and Andy Gill, \"/Fast Mergeable Integer Maps/\",
25 -- Workshop on ML, September 1998, pages 77-86,
26 -- <http://www.cse.ogi.edu/~andy/pub/finite.htm>
28 -- * D.R. Morrison, \"/PATRICIA -- Practical Algorithm To Retrieve
29 -- Information Coded In Alphanumeric/\", Journal of the ACM, 15(4),
30 -- October 1968, pages 514-534.
32 -- Many operations have a worst-case complexity of /O(min(n,W))/.
33 -- This means that the operation can become linear in the number of
34 -- elements with a maximum of /W/ -- the number of bits in an 'Int'
36 -----------------------------------------------------------------------------
40 IntSet -- instance Eq,Show
92 import Prelude hiding (lookup,filter,foldr,foldl,null,map)
96 import qualified Data.List as List
103 import List (nub,sort)
104 import qualified List
107 #if __GLASGOW_HASKELL__ >= 503
109 import GHC.Exts ( Word(..), Int(..), shiftRL# )
110 #elif __GLASGOW_HASKELL__
112 import GlaExts ( Word(..), Int(..), shiftRL# )
117 infixl 9 \\{-This comment teaches CPP correct behaviour -}
119 -- A "Nat" is a natural machine word (an unsigned Int)
122 natFromInt :: Int -> Nat
123 natFromInt i = fromIntegral i
125 intFromNat :: Nat -> Int
126 intFromNat w = fromIntegral w
128 shiftRL :: Nat -> Int -> Nat
129 #if __GLASGOW_HASKELL__
130 {--------------------------------------------------------------------
131 GHC: use unboxing to get @shiftRL@ inlined.
132 --------------------------------------------------------------------}
133 shiftRL (W# x) (I# i)
136 shiftRL x i = shiftR x i
139 {--------------------------------------------------------------------
141 --------------------------------------------------------------------}
142 -- | /O(n+m)/. See 'difference'.
143 (\\) :: IntSet -> IntSet -> IntSet
144 m1 \\ m2 = difference m1 m2
146 {--------------------------------------------------------------------
148 --------------------------------------------------------------------}
149 -- | A set of integers.
151 | Tip {-# UNPACK #-} !Int
152 | Bin {-# UNPACK #-} !Prefix {-# UNPACK #-} !Mask !IntSet !IntSet
157 {--------------------------------------------------------------------
159 --------------------------------------------------------------------}
160 -- | /O(1)/. Is the set empty?
161 null :: IntSet -> Bool
165 -- | /O(n)/. Cardinality of the set.
166 size :: IntSet -> Int
169 Bin p m l r -> size l + size r
173 -- | /O(min(n,W))/. Is the value a member of the set?
174 member :: Int -> IntSet -> Bool
178 | nomatch x p m -> False
179 | zero x m -> member x l
180 | otherwise -> member x r
184 -- 'lookup' is used by 'intersection' for left-biasing
185 lookup :: Int -> IntSet -> Maybe Int
187 = let nk = natFromInt k in seq nk (lookupN nk t)
189 lookupN :: Nat -> IntSet -> Maybe Int
193 | zeroN k (natFromInt m) -> lookupN k l
194 | otherwise -> lookupN k r
196 | (k == natFromInt kx) -> Just kx
197 | otherwise -> Nothing
200 {--------------------------------------------------------------------
202 --------------------------------------------------------------------}
203 -- | /O(1)/. The empty set.
208 -- | /O(1)/. A set of one element.
209 singleton :: Int -> IntSet
213 {--------------------------------------------------------------------
215 --------------------------------------------------------------------}
216 -- | /O(min(n,W))/. Add a value to the set. When the value is already
217 -- an element of the set, it is replaced by the new one, ie. 'insert'
219 insert :: Int -> IntSet -> IntSet
223 | nomatch x p m -> join x (Tip x) p t
224 | zero x m -> Bin p m (insert x l) r
225 | otherwise -> Bin p m l (insert x r)
228 | otherwise -> join x (Tip x) y t
231 -- right-biased insertion, used by 'union'
232 insertR :: Int -> IntSet -> IntSet
236 | nomatch x p m -> join x (Tip x) p t
237 | zero x m -> Bin p m (insert x l) r
238 | otherwise -> Bin p m l (insert x r)
241 | otherwise -> join x (Tip x) y t
244 -- | /O(min(n,W))/. Delete a value in the set. Returns the
245 -- original set when the value was not present.
246 delete :: Int -> IntSet -> IntSet
251 | zero x m -> bin p m (delete x l) r
252 | otherwise -> bin p m l (delete x r)
259 {--------------------------------------------------------------------
261 --------------------------------------------------------------------}
262 -- | The union of a list of sets.
263 unions :: [IntSet] -> IntSet
265 = foldlStrict union empty xs
268 -- | /O(n+m)/. The union of two sets.
269 union :: IntSet -> IntSet -> IntSet
270 union t1@(Bin p1 m1 l1 r1) t2@(Bin p2 m2 l2 r2)
271 | shorter m1 m2 = union1
272 | shorter m2 m1 = union2
273 | p1 == p2 = Bin p1 m1 (union l1 l2) (union r1 r2)
274 | otherwise = join p1 t1 p2 t2
276 union1 | nomatch p2 p1 m1 = join p1 t1 p2 t2
277 | zero p2 m1 = Bin p1 m1 (union l1 t2) r1
278 | otherwise = Bin p1 m1 l1 (union r1 t2)
280 union2 | nomatch p1 p2 m2 = join p1 t1 p2 t2
281 | zero p1 m2 = Bin p2 m2 (union t1 l2) r2
282 | otherwise = Bin p2 m2 l2 (union t1 r2)
284 union (Tip x) t = insert x t
285 union t (Tip x) = insertR x t -- right bias
290 {--------------------------------------------------------------------
292 --------------------------------------------------------------------}
293 -- | /O(n+m)/. Difference between two sets.
294 difference :: IntSet -> IntSet -> IntSet
295 difference t1@(Bin p1 m1 l1 r1) t2@(Bin p2 m2 l2 r2)
296 | shorter m1 m2 = difference1
297 | shorter m2 m1 = difference2
298 | p1 == p2 = bin p1 m1 (difference l1 l2) (difference r1 r2)
301 difference1 | nomatch p2 p1 m1 = t1
302 | zero p2 m1 = bin p1 m1 (difference l1 t2) r1
303 | otherwise = bin p1 m1 l1 (difference r1 t2)
305 difference2 | nomatch p1 p2 m2 = t1
306 | zero p1 m2 = difference t1 l2
307 | otherwise = difference t1 r2
309 difference t1@(Tip x) t2
313 difference Nil t = Nil
314 difference t (Tip x) = delete x t
319 {--------------------------------------------------------------------
321 --------------------------------------------------------------------}
322 -- | /O(n+m)/. The intersection of two sets.
323 intersection :: IntSet -> IntSet -> IntSet
324 intersection t1@(Bin p1 m1 l1 r1) t2@(Bin p2 m2 l2 r2)
325 | shorter m1 m2 = intersection1
326 | shorter m2 m1 = intersection2
327 | p1 == p2 = bin p1 m1 (intersection l1 l2) (intersection r1 r2)
330 intersection1 | nomatch p2 p1 m1 = Nil
331 | zero p2 m1 = intersection l1 t2
332 | otherwise = intersection r1 t2
334 intersection2 | nomatch p1 p2 m2 = Nil
335 | zero p1 m2 = intersection t1 l2
336 | otherwise = intersection t1 r2
338 intersection t1@(Tip x) t2
341 intersection t (Tip x)
345 intersection Nil t = Nil
346 intersection t Nil = Nil
350 {--------------------------------------------------------------------
352 --------------------------------------------------------------------}
353 -- | /O(n+m)/. Is this a proper subset? (ie. a subset but not equal).
354 isProperSubsetOf :: IntSet -> IntSet -> Bool
355 isProperSubsetOf t1 t2
356 = case subsetCmp t1 t2 of
360 subsetCmp t1@(Bin p1 m1 l1 r1) t2@(Bin p2 m2 l2 r2)
362 | shorter m2 m1 = subsetCmpLt
363 | p1 == p2 = subsetCmpEq
364 | otherwise = GT -- disjoint
366 subsetCmpLt | nomatch p1 p2 m2 = GT
367 | zero p1 m2 = subsetCmp t1 l2
368 | otherwise = subsetCmp t1 r2
369 subsetCmpEq = case (subsetCmp l1 l2, subsetCmp r1 r2) of
375 subsetCmp (Bin p m l r) t = GT
376 subsetCmp (Tip x) (Tip y)
378 | otherwise = GT -- disjoint
381 | otherwise = GT -- disjoint
382 subsetCmp Nil Nil = EQ
385 -- | /O(n+m)/. Is this a subset?
386 -- @(s1 `isSubsetOf` s2)@ tells whether s1 is a subset of s2.
388 isSubsetOf :: IntSet -> IntSet -> Bool
389 isSubsetOf t1@(Bin p1 m1 l1 r1) t2@(Bin p2 m2 l2 r2)
390 | shorter m1 m2 = False
391 | shorter m2 m1 = match p1 p2 m2 && (if zero p1 m2 then isSubsetOf t1 l2
392 else isSubsetOf t1 r2)
393 | otherwise = (p1==p2) && isSubsetOf l1 l2 && isSubsetOf r1 r2
394 isSubsetOf (Bin p m l r) t = False
395 isSubsetOf (Tip x) t = member x t
396 isSubsetOf Nil t = True
399 {--------------------------------------------------------------------
401 --------------------------------------------------------------------}
402 -- | /O(n)/. Filter all elements that satisfy some predicate.
403 filter :: (Int -> Bool) -> IntSet -> IntSet
407 -> bin p m (filter pred l) (filter pred r)
413 -- | /O(n)/. partition the set according to some predicate.
414 partition :: (Int -> Bool) -> IntSet -> (IntSet,IntSet)
418 -> let (l1,l2) = partition pred l
419 (r1,r2) = partition pred r
420 in (bin p m l1 r1, bin p m l2 r2)
423 | otherwise -> (Nil,t)
427 -- | /O(log n)/. The expression (@split x set@) is a pair @(set1,set2)@
428 -- where all elements in @set1@ are lower than @x@ and all elements in
429 -- @set2@ larger than @x@.
431 -- > split 3 (fromList [1..5]) == (fromList [1,2], fromList [3,4])
432 split :: Int -> IntSet -> (IntSet,IntSet)
436 | zero x m -> let (lt,gt) = split x l in (lt,union gt r)
437 | otherwise -> let (lt,gt) = split x r in (union l lt,gt)
441 | otherwise -> (Nil,Nil)
444 -- | /O(log n)/. Performs a 'split' but also returns whether the pivot
445 -- element was found in the original set.
446 splitMember :: Int -> IntSet -> (Bool,IntSet,IntSet)
450 | zero x m -> let (found,lt,gt) = splitMember x l in (found,lt,union gt r)
451 | otherwise -> let (found,lt,gt) = splitMember x r in (found,union l lt,gt)
453 | x>y -> (False,t,Nil)
454 | x<y -> (False,Nil,t)
455 | otherwise -> (True,Nil,Nil)
456 Nil -> (False,Nil,Nil)
458 {----------------------------------------------------------------------
460 ----------------------------------------------------------------------}
462 -- | /O(n*min(n,W))/.
463 -- @map f s@ is the set obtained by applying @f@ to each element of @s@.
465 -- It's worth noting that the size of the result may be smaller if,
466 -- for some @(x,y)@, @x \/= y && f x == f y@
468 map :: (Int->Int) -> IntSet -> IntSet
469 map f = fromList . List.map f . toList
471 {--------------------------------------------------------------------
473 --------------------------------------------------------------------}
474 -- | /O(n)/. Fold over the elements of a set in an unspecified order.
476 -- > sum set == fold (+) 0 set
477 -- > elems set == fold (:) [] set
478 fold :: (Int -> b -> b) -> b -> IntSet -> b
482 foldr :: (Int -> b -> b) -> b -> IntSet -> b
485 Bin p m l r -> foldr f (foldr f z r) l
489 {--------------------------------------------------------------------
491 --------------------------------------------------------------------}
492 -- | /O(n)/. The elements of a set. (For sets, this is equivalent to toList)
493 elems :: IntSet -> [Int]
497 {--------------------------------------------------------------------
499 --------------------------------------------------------------------}
500 -- | /O(n)/. Convert the set to a list of elements.
501 toList :: IntSet -> [Int]
505 -- | /O(n)/. Convert the set to an ascending list of elements.
506 toAscList :: IntSet -> [Int]
508 = -- NOTE: the following algorithm only works for big-endian trees
509 let (pos,neg) = span (>=0) (foldr (:) [] t) in neg ++ pos
511 -- | /O(n*min(n,W))/. Create a set from a list of integers.
512 fromList :: [Int] -> IntSet
514 = foldlStrict ins empty xs
518 -- | /O(n*min(n,W))/. Build a set from an ascending list of elements.
519 fromAscList :: [Int] -> IntSet
523 -- | /O(n*min(n,W))/. Build a set from an ascending list of distinct elements.
524 fromDistinctAscList :: [Int] -> IntSet
525 fromDistinctAscList xs
529 {--------------------------------------------------------------------
531 --------------------------------------------------------------------}
532 instance Eq IntSet where
533 t1 == t2 = equal t1 t2
534 t1 /= t2 = nequal t1 t2
536 equal :: IntSet -> IntSet -> Bool
537 equal (Bin p1 m1 l1 r1) (Bin p2 m2 l2 r2)
538 = (m1 == m2) && (p1 == p2) && (equal l1 l2) && (equal r1 r2)
539 equal (Tip x) (Tip y)
544 nequal :: IntSet -> IntSet -> Bool
545 nequal (Bin p1 m1 l1 r1) (Bin p2 m2 l2 r2)
546 = (m1 /= m2) || (p1 /= p2) || (nequal l1 l2) || (nequal r1 r2)
547 nequal (Tip x) (Tip y)
549 nequal Nil Nil = False
552 {--------------------------------------------------------------------
554 --------------------------------------------------------------------}
556 instance Ord IntSet where
557 compare s1 s2 = compare (toAscList s1) (toAscList s2)
558 -- tentative implementation. See if more efficient exists.
560 {--------------------------------------------------------------------
562 --------------------------------------------------------------------}
564 instance Monoid IntSet where
569 {--------------------------------------------------------------------
571 --------------------------------------------------------------------}
572 instance Show IntSet where
573 showsPrec d s = showSet (toList s)
575 showSet :: [Int] -> ShowS
579 = showChar '{' . shows x . showTail xs
581 showTail [] = showChar '}'
582 showTail (x:xs) = showChar ',' . shows x . showTail xs
584 {--------------------------------------------------------------------
586 --------------------------------------------------------------------}
588 #include "Typeable.h"
589 INSTANCE_TYPEABLE0(IntSet,intSetTc,"IntSet")
591 {--------------------------------------------------------------------
593 --------------------------------------------------------------------}
594 -- | /O(n)/. Show the tree that implements the set. The tree is shown
595 -- in a compressed, hanging format.
596 showTree :: IntSet -> String
598 = showTreeWith True False s
601 {- | /O(n)/. The expression (@showTreeWith hang wide map@) shows
602 the tree that implements the set. If @hang@ is
603 @True@, a /hanging/ tree is shown otherwise a rotated tree is shown. If
604 @wide@ is true, an extra wide version is shown.
606 showTreeWith :: Bool -> Bool -> IntSet -> String
607 showTreeWith hang wide t
608 | hang = (showsTreeHang wide [] t) ""
609 | otherwise = (showsTree wide [] [] t) ""
611 showsTree :: Bool -> [String] -> [String] -> IntSet -> ShowS
612 showsTree wide lbars rbars t
615 -> showsTree wide (withBar rbars) (withEmpty rbars) r .
616 showWide wide rbars .
617 showsBars lbars . showString (showBin p m) . showString "\n" .
618 showWide wide lbars .
619 showsTree wide (withEmpty lbars) (withBar lbars) l
621 -> showsBars lbars . showString " " . shows x . showString "\n"
622 Nil -> showsBars lbars . showString "|\n"
624 showsTreeHang :: Bool -> [String] -> IntSet -> ShowS
625 showsTreeHang wide bars t
628 -> showsBars bars . showString (showBin p m) . showString "\n" .
630 showsTreeHang wide (withBar bars) l .
632 showsTreeHang wide (withEmpty bars) r
634 -> showsBars bars . showString " " . shows x . showString "\n"
635 Nil -> showsBars bars . showString "|\n"
638 = "*" -- ++ show (p,m)
641 | wide = showString (concat (reverse bars)) . showString "|\n"
644 showsBars :: [String] -> ShowS
648 _ -> showString (concat (reverse (tail bars))) . showString node
651 withBar bars = "| ":bars
652 withEmpty bars = " ":bars
655 {--------------------------------------------------------------------
657 --------------------------------------------------------------------}
658 {--------------------------------------------------------------------
660 --------------------------------------------------------------------}
661 join :: Prefix -> IntSet -> Prefix -> IntSet -> IntSet
663 | zero p1 m = Bin p m t1 t2
664 | otherwise = Bin p m t2 t1
669 {--------------------------------------------------------------------
670 @bin@ assures that we never have empty trees within a tree.
671 --------------------------------------------------------------------}
672 bin :: Prefix -> Mask -> IntSet -> IntSet -> IntSet
675 bin p m l r = Bin p m l r
678 {--------------------------------------------------------------------
679 Endian independent bit twiddling
680 --------------------------------------------------------------------}
681 zero :: Int -> Mask -> Bool
683 = (natFromInt i) .&. (natFromInt m) == 0
685 nomatch,match :: Int -> Prefix -> Mask -> Bool
692 mask :: Int -> Mask -> Prefix
694 = maskW (natFromInt i) (natFromInt m)
696 zeroN :: Nat -> Nat -> Bool
697 zeroN i m = (i .&. m) == 0
699 {--------------------------------------------------------------------
700 Big endian operations
701 --------------------------------------------------------------------}
702 maskW :: Nat -> Nat -> Prefix
704 = intFromNat (i .&. (complement (m-1) `xor` m))
706 shorter :: Mask -> Mask -> Bool
708 = (natFromInt m1) > (natFromInt m2)
710 branchMask :: Prefix -> Prefix -> Mask
712 = intFromNat (highestBitMask (natFromInt p1 `xor` natFromInt p2))
714 {----------------------------------------------------------------------
715 Finding the highest bit (mask) in a word [x] can be done efficiently in
717 * convert to a floating point value and the mantissa tells us the
718 [log2(x)] that corresponds with the highest bit position. The mantissa
719 is retrieved either via the standard C function [frexp] or by some bit
720 twiddling on IEEE compatible numbers (float). Note that one needs to
721 use at least [double] precision for an accurate mantissa of 32 bit
723 * use bit twiddling, a logarithmic sequence of bitwise or's and shifts (bit).
724 * use processor specific assembler instruction (asm).
726 The most portable way would be [bit], but is it efficient enough?
727 I have measured the cycle counts of the different methods on an AMD
728 Athlon-XP 1800 (~ Pentium III 1.8Ghz) using the RDTSC instruction:
730 highestBitMask: method cycles
737 highestBit: method cycles
744 Wow, the bit twiddling is on today's RISC like machines even faster
745 than a single CISC instruction (BSR)!
746 ----------------------------------------------------------------------}
748 {----------------------------------------------------------------------
749 [highestBitMask] returns a word where only the highest bit is set.
750 It is found by first setting all bits in lower positions than the
751 highest bit and than taking an exclusive or with the original value.
752 Allthough the function may look expensive, GHC compiles this into
753 excellent C code that subsequently compiled into highly efficient
754 machine code. The algorithm is derived from Jorg Arndt's FXT library.
755 ----------------------------------------------------------------------}
756 highestBitMask :: Nat -> Nat
758 = case (x .|. shiftRL x 1) of
759 x -> case (x .|. shiftRL x 2) of
760 x -> case (x .|. shiftRL x 4) of
761 x -> case (x .|. shiftRL x 8) of
762 x -> case (x .|. shiftRL x 16) of
763 x -> case (x .|. shiftRL x 32) of -- for 64 bit platforms
764 x -> (x `xor` (shiftRL x 1))
767 {--------------------------------------------------------------------
769 --------------------------------------------------------------------}
773 (x:xx) -> let z' = f z x in seq z' (foldlStrict f z' xx)
777 {--------------------------------------------------------------------
779 --------------------------------------------------------------------}
780 testTree :: [Int] -> IntSet
781 testTree xs = fromList xs
782 test1 = testTree [1..20]
783 test2 = testTree [30,29..10]
784 test3 = testTree [1,4,6,89,2323,53,43,234,5,79,12,9,24,9,8,423,8,42,4,8,9,3]
786 {--------------------------------------------------------------------
788 --------------------------------------------------------------------}
793 { configMaxTest = 500
794 , configMaxFail = 5000
795 , configSize = \n -> (div n 2 + 3)
796 , configEvery = \n args -> let s = show n in s ++ [ '\b' | _ <- s ]
800 {--------------------------------------------------------------------
801 Arbitrary, reasonably balanced trees
802 --------------------------------------------------------------------}
803 instance Arbitrary IntSet where
804 arbitrary = do{ xs <- arbitrary
805 ; return (fromList xs)
809 {--------------------------------------------------------------------
810 Single, Insert, Delete
811 --------------------------------------------------------------------}
812 prop_Single :: Int -> Bool
814 = (insert x empty == singleton x)
816 prop_InsertDelete :: Int -> IntSet -> Property
817 prop_InsertDelete k t
818 = not (member k t) ==> delete k (insert k t) == t
821 {--------------------------------------------------------------------
823 --------------------------------------------------------------------}
824 prop_UnionInsert :: Int -> IntSet -> Bool
826 = union t (singleton x) == insert x t
828 prop_UnionAssoc :: IntSet -> IntSet -> IntSet -> Bool
829 prop_UnionAssoc t1 t2 t3
830 = union t1 (union t2 t3) == union (union t1 t2) t3
832 prop_UnionComm :: IntSet -> IntSet -> Bool
834 = (union t1 t2 == union t2 t1)
836 prop_Diff :: [Int] -> [Int] -> Bool
838 = toAscList (difference (fromList xs) (fromList ys))
839 == List.sort ((List.\\) (nub xs) (nub ys))
841 prop_Int :: [Int] -> [Int] -> Bool
843 = toAscList (intersection (fromList xs) (fromList ys))
844 == List.sort (nub ((List.intersect) (xs) (ys)))
846 {--------------------------------------------------------------------
848 --------------------------------------------------------------------}
850 = forAll (choose (5,100)) $ \n ->
852 in fromAscList xs == fromList xs
854 prop_List :: [Int] -> Bool
856 = (sort (nub xs) == toAscList (fromList xs))