I think it likes a trap. See this. Data.ByteString.unpack . Data.ByteString.pack $! ([0,17..255] ++ [1,18..256]) Without thinking about for Word8, [1,18..256] is equal to [1,18..0]. Though I try to use "$!" to let GHC generate the list as Integer. It would not do so. :-L ------------------ L.Guo 2007-05-25