Re: [Haskell-cafe] Bug in writeArray?
2009/9/23 Bulat Ziganshin bulat.zigans...@gmail.com: Hello Grzegorz, Wednesday, September 23, 2009, 7:19:59 PM, you wrote: This seems like a bug in the implementation of writeArray: when passed let (l,u) = ((0,10),(20,20)) writeArray computes raw index (from 0 to total number of array elements) and check that this index is correct. with multi-dimensional arrays this approach may lead to wrong results, as you mentioned. it's known problem that isn't fixed for a long time probably due to efficiency cautions. Hmm, I understand that efficiency is an issue, but in that case shouldn't unsafe writing be provided by and unsafeWriteArray function, while writeArray does proper range checking? Or at least this problem with writeArray should be clearly indicated in the documentation. I for one spent several hours debugging before finding out about this lack of proper range checks so it's not an imaginary problem. -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bug in writeArray?
I agree with Grzegorz. Perhaps we should file a bug-report, if there isn't one already? -Iavor 2009/9/24 Grzegorz Chrupała pite...@gmail.com: 2009/9/23 Bulat Ziganshin bulat.zigans...@gmail.com: Hello Grzegorz, Wednesday, September 23, 2009, 7:19:59 PM, you wrote: This seems like a bug in the implementation of writeArray: when passed let (l,u) = ((0,10),(20,20)) writeArray computes raw index (from 0 to total number of array elements) and check that this index is correct. with multi-dimensional arrays this approach may lead to wrong results, as you mentioned. it's known problem that isn't fixed for a long time probably due to efficiency cautions. Hmm, I understand that efficiency is an issue, but in that case shouldn't unsafe writing be provided by and unsafeWriteArray function, while writeArray does proper range checking? Or at least this problem with writeArray should be clearly indicated in the documentation. I for one spent several hours debugging before finding out about this lack of proper range checks so it's not an imaginary problem. -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bug in writeArray?
2009/9/24 Iavor Diatchki iavor.diatc...@gmail.com: I agree with Grzegorz. Perhaps we should file a bug-report, if there isn't one already? http://hackage.haskell.org/trac/ghc/ticket/2120 Apparently, it's fixed in GHC 6.12. -- Dave Menendez d...@zednenem.com http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bug in writeArray?
On Thu, 2009-09-24 at 13:53 +0200, Grzegorz Chrupała wrote: 2009/9/23 Bulat Ziganshin bulat.zigans...@gmail.com: Hello Grzegorz, Wednesday, September 23, 2009, 7:19:59 PM, you wrote: This seems like a bug in the implementation of writeArray: when passed let (l,u) = ((0,10),(20,20)) writeArray computes raw index (from 0 to total number of array elements) and check that this index is correct. with multi-dimensional arrays this approach may lead to wrong results, as you mentioned. it's known problem that isn't fixed for a long time probably due to efficiency cautions. Hmm, I understand that efficiency is an issue, but in that case shouldn't unsafe writing be provided by and unsafeWriteArray function, while writeArray does proper range checking? Or at least this problem with writeArray should be clearly indicated in the documentation. I for one spent several hours debugging before finding out about this lack of proper range checks so it's not an imaginary problem. It's now fixed: http://hackage.haskell.org/trac/ghc/ticket/2120#comment:13 Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Bug in writeArray?
Hi all, This seems like a bug in the implementation of writeArray: when passed an out-of-range index it silently writes to an incorrect index in the array. -- import Data.Array.IO import Data.Array.Unboxed main = do let (l,u) = ((0,10),(20,20)) marr - newArray (l,u) 0 :: IO (IOUArray (Int,Int) Int) let badi = (10,9) print (inRange (l,u) badi) writeArray marr badi 1 arr - freeze marr :: IO (UArray (Int,Int) Int) print . filter ((/=0) . snd) . assocs $ arr -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bug in writeArray?
Hello Grzegorz, Wednesday, September 23, 2009, 7:19:59 PM, you wrote: This seems like a bug in the implementation of writeArray: when passed let (l,u) = ((0,10),(20,20)) writeArray computes raw index (from 0 to total number of array elements) and check that this index is correct. with multi-dimensional arrays this approach may lead to wrong results, as you mentioned. it's known problem that isn't fixed for a long time probably due to efficiency cautions. the error is here: data Ix i = Array i e = Array !i -- the lower bound, l !i -- the upper bound, u !Int -- a cache of (rangeSize (l,u)) -- used to make sure an index is -- really in range (Array# e) -- The actual elements (!) :: Ix i = Array i e - i - e arr@(Array l u n _) ! i = unsafeAt arr $ safeIndex (l,u) n i safeIndex :: Ix i = (i, i) - Int - i - Int safeIndex (l,u) n i = let i' = unsafeIndex (l,u) i in if (0 = i') (i' n) then i' else error Error in array index obviously, safeIndex should use inRange call instead -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
