bitset (empty) → 0.5

raw patch · 4 files changed

+301/−0 lines, 4 filesdep +QuickCheckdep +basesetup-changed

Dependencies added: QuickCheck, base

Files

• COPYING +165/−0
• Data/BitSet.hs +117/−0
• Setup.lhs +4/−0
• bitset.cabal +15/−0

@@ -0,0 +1,165 @@+		   GNU LESSER GENERAL PUBLIC LICENSE+                       Version 3, 29 June 2007++ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>+ Everyone is permitted to copy and distribute verbatim copies+ of this license document, but changing it is not allowed.+++  This version of the GNU Lesser General Public License incorporates+the terms and conditions of version 3 of the GNU General Public+License, supplemented by the additional permissions listed below.++  0. 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@@ -0,0 +1,117 @@+-- | An efficient membership-testing module, for types that can be mapped into+-- @Int@s.+--+-- The implementation is quite simple: we rely on the @Bits Integer@ instance+-- from @Data.Bits@ for the three main operations.  An advantage of this+-- library is the phantom parameter used in the BitSet type.  Since there is+-- no exported way to construct a value of type `BitSet' directly, the+-- interface we expose ensures client code will not typecheck if it confuses+-- two bit sets intended to keep track of different types.+--+-- It is important that the values you intend to keep track of start from 0+-- and go up.  Each @Int@ mapped to be hash corresponds to that bit location in+-- an @Integer@, and thus requires that @Integer@ to have at least that many+-- bits.  Don't shoot yourself in the foot.+module Data.BitSet+    ( Hash(..)+    , BitSet+    , empty+    , insert+    , delete+    , member+    ) where++import Data.Bits++import Test.QuickCheck++-- | Map a value to an non-negative @Int@.+--+-- For the implementation to give reliable results, it must be that if @hash x+-- == hash y@, @x@ and @y@ are equivalent under the relevant relation used in+-- the client code.  (We don't depend on equality, but the client code will+-- certainly want to use the above sort of inference.)+--+-- In fact, if your equivalence relation is @==@, the following quickcheck+-- test should pass, for arbitrary @x@ and @y@:+--+-- @prop_hash x y =+--     if hash x == hash y then x == y+--     else x /= y+--     && if x == y then hash x == hash y+--        else hash x /= hash y@+class Hash a where+    hash :: a -> Int++-- | The @Show@ instance kind of sucks.  It just shows the @Integer@+-- representation.  A good show would probably show all the present hashes.+newtype BitSet a = BS { unBS :: Integer }+    deriving (Eq)++instance Show (BitSet a) where+    show s = "BitSet " ++ show (unBS s)++-- | The empty bit set.+empty :: BitSet a++-- | /O(setBit on Integer)/ Insert an item into the bit set.+insert :: Hash a => a -> BitSet a -> BitSet a++-- | /O(clearBit on Integer)/ Delete an item from the bit set.+delete :: Hash a => a -> BitSet a -> BitSet a++-- | /O(testBit on Integer)/ Ask whether the item is in the bit set.+member :: Hash a => a -> BitSet a -> Bool+++-- * Implementation++empty = BS 0++{-# INLINE insert #-}+insert x s = BS $ setBit (unBS s) (hash x)++{-# INLINE delete #-}+delete x s = BS $ clearBit (unBS s) (hash x)++{-# INLINE member #-}+member x s = testBit (unBS s) (hash x)++-- * Default instances++instance Hash Int where+    hash = id++instance Hash Integer where+    hash = fromIntegral++-- Needs UndecidableInstances?+-- instance Integral a => Hash a where+--     hash = fromIntegral++-- * Quickcheck properties++instance Arbitrary (BitSet a) where+    arbitrary = sized $ \n -> return $ BS $ fromIntegral n++prop_insert x s = xa `member` insert xa s+    where xa = abs x :: Int++prop_delete x s = not $ xa `member` delete xa s+    where xa = abs x :: Int++prop_insDelIdempotent x = empty == (delete xa . insert xa $ empty)+    where xa = abs x :: Int++prop_delDelIdempotent x s = delete xa s == (delete xa . delete xa $ s)+    where xa = abs x :: Int++prop_insInsIdempotent x s = insert xa s == (insert xa . insert xa $ s)+    where xa = abs x :: Int++prop_extensional xs = and $ map (`member` s) xsa+    where s = foldr insert empty xsa+          xsa = map abs xs :: [Int]++prop_empty x = not $ xa `member` empty+    where xa = abs x :: Int

@@ -0,0 +1,4 @@+#! /usr/bin/env runhaskell++> import Distribution.Simple+> main = defaultMain

@@ -0,0 +1,15 @@+Name:                bitset+Version:             0.5+Synopsis:            A functional data structure for efficient membership testing.+Description:         A bit set is a data structure for keeping membership information efficiently.  This implementation uses Data.Bits on Integers, and thus should achieve reasonable speed.+Category:            Data Structures+License:             LGPL+License-file:        COPYING+Author:              Denis Bueno+Maintainer:          Denis Bueno <dbueno@gmail.com>+Stability:           provisional+Build-Depends:       base, QuickCheck+Build-type:          Simple++Exposed-modules:     Data.BitSet+Ghc-options:         -W