Data.ByteString.Lazy.elemIndices returns wrong results
elemIndices for Lazy ByteString returns wrong results occasionally for huge input.
-- lei.hs
import qualified Data.ByteString.Lazy as L
import Control.Monad
main = do
n <- fmap (length . L.elemIndices 10) L.getContents
putStrLn (show n)
$ ghc --make lei
[1 of 1] Compiling Main ( lei.hs, lei.o )
Linking lei ...
$ yes | head -1000000 | ./lei
1000000
$ yes | head -1000000 | ./lei
999992
$ yes | head -1000000 | ./lei
999960
$ yes | head -1000000 | ./lei
1000000
$ yes | head -1000000 | ./lei
999976
Without getContents, elemIndices works fine.
import qualified Data.ByteString.Lazy as L
import System.Environment
main = do
n <- fmap (read . head) getArgs
let cs = L.pack . take (2*n) . cycle $ [48,10]
ps = L.elemIndices 10 cs
print (length ps)
$ ghc --make lei2.hs
[1 of 1] Compiling Main ( lei2.hs, lei2.o )
Linking lei2 ...
$ ./lei2 1000000
1000000
$ ./lei2 1000000
1000000
So I think there is a problem about bytestring IO.
And I heard this isn't reproduced in Windows' command prompt.
This ticket is based on a thread of haskell-jp.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.4 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | libraries/base |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |