[project @ 2004-09-15 13:51:00 by stolz]

[ghc-base.git] / Data / HashTable.hs

diff --git a/Data/HashTable.hs b/Data/HashTable.hs
index 0429797..37ddb5e 100644 (file)
--- a/Data/HashTable.hs
+++ b/Data/HashTable.hs
@@ -41,7 +41,7 @@ import Prelude        hiding  ( lookup )
 import Data.Tuple      ( fst )
 import Data.Bits
 import Data.Maybe
-import Data.List       ( maximumBy, filter, length, concat )
+import Data.List       ( maximumBy, filter, length, concat, foldl )
 import Data.Int                ( Int32 )
 
 #if defined(__GLASGOW_HASKELL__)
@@ -153,11 +153,12 @@ hashInt = (`rem` prime) . fromIntegral
 -- which seems to give reasonable results.
 --
 hashString :: String -> Int32
-hashString = fromIntegral . foldr f 0
-  where f c m = ord c + (m * 128) `rem` fromIntegral prime
+hashString = fromIntegral . foldl f 0
+  where f m c = ord c + (m * 128) `rem` fromIntegral prime
 
 -- | A prime larger than the maximum hash table size
-prime = 1500007 :: Int32
+prime :: Int32
+prime = 1500007
 
 -- -----------------------------------------------------------------------------
 -- Parameters
@@ -174,10 +175,14 @@ hLOAD = 4 :: Int32 -- Maximum average load of a single hash bucket
 -- -----------------------------------------------------------------------------
 -- Creating a new hash table
 
--- | Creates a new hash table
+-- | Creates a new hash table.  The following property should hold for the @eq@
+-- and @hash@ functions passed to 'new':
+--
+-- >   eq A B  =>  hash A == hash B
+--
 new
-  :: (key -> key -> Bool)    -- ^ An equality comparison on keys
-  -> (key -> Int32)         -- ^ A hash function on keys
+  :: (key -> key -> Bool)    -- ^ @eq@: An equality comparison on keys
+  -> (key -> Int32)         -- ^ @hash@: A hash function on keys
   -> IO (HashTable key val)  -- ^ Returns: an empty hash table
 
 new cmp hash_fn = do
@@ -215,7 +220,7 @@ insert (HashTable ref) key val = do
           then expandHashTable table1
           else return table1
   writeIORef ref table2
-  (segment_index,segment_offset) <- tableLocation table key
+  (segment_index,segment_offset) <- tableLocation table2 key
   segment <- myReadArray dir segment_index
   bucket <- myReadArray segment segment_offset
   myWriteArray segment segment_offset ((key,val):bucket)
@@ -249,6 +254,7 @@ expandHashTable
       table@HT{ dir=dir,
                split=split,
                max_bucket=max,
+               bcount=bcount,
                mask2=mask2 } = do
   let
       oldsegment = split `shiftR` sEGMENT_SHIFT
@@ -264,10 +270,12 @@ expandHashTable
   --
   let table' =
        if (split+1) < max
-           then table{ split = split+1 }
+           then table{ split = split+1,
+                       bcount = bcount+1 }
                -- we've expanded all the buckets in this table, so start from
                -- the beginning again.
            else table{ split = 0,
+                       bcount = bcount+1,
                        max_bucket = max * 2,
                        mask1 = mask2,
                        mask2 = mask2 `shiftL` 1 .|. 1 }