#661: Serious Data.HashTable bug
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Reporter: [EMAIL PROTECTED] | Owner:
Type: bug | Status: new
Priority: high | Milestone:
Component: libraries/base | Version: 6.4.1
Severity: major | Keywords:
Os: Unknown | Difficulty: Unknown
Architecture: Unknown |
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The program below illustrates a difference between the
description of the semantics of insert (given below)
and the implementation. Try calling the function "test"
with values greater than 2047. For instance:
HT> test 2048
0
1024
The documentation states:
insert :: HashTable key val -> key -> val -> IO ()
Inserts an key/value mapping into the hash table.
Note that insert doesn't remove the old entry from the table
- the behaviour is like an association list, where lookup returns
the most-recently-inserted mapping for a key in the table.
The reason for this is to keep insert as efficient as possible.
If you need to update a mapping, then we provide update.
{{{
module HT where
import Data.HashTable
import qualified Data.HashTable as HT
test :: Int -> IO ()
test n = do ht <- new (==) hashInt
sequence_ [ insert ht key 0 | key <- [0..n]]
sequence_ [ insert ht key 1 | key <- [0..n]]
let check key = do (Just val) <- HT.lookup ht key
if val==1 then return () else putStrLn $
show key
sequence_ [ check key | key <- [0..n]]
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/661>
GHC <http://www.haskell.org/ghc/>
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