[Haskell-cafe] Crash in Data.ByteString.Lazy.hPut
Hi there, Not sure where to raise bugs in hackage libraries, so I'm posting here. If there is a better place, please let me know. The following code crashes with a divide by zero error when using the package 'binary-0.4.' module Main where import IO import Data.Binary import Data.Binary.Put import qualified Data.ByteString.Lazy as B simpleImage = take tot (map (\x - x `mod` 256) [1..]) where tot = 640 * 480 main = do output - openFile test.tmp WriteMode B.hPut output $ runPut $ mapM_ putWord8 simpleImage -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Crash in Data.ByteString.Lazy.hPut
Oh, I see I wasn't thinking through the code (and I'm still in the honeymoon phase with Haskell, thinking it can do no wrong). Don Stewart wrote: jamie.love: Ah, of course. Thanks. I removed the hPut and it runs smoothly. I had forgotten that haskell chooses the types dynamically. Shouldn't haskell pick up that there is no 'mod' for Word8? I mean, shouldn't I get a nicer error message? Well, it inferred Word8 for your generated values, so 256 overflowed to 0. Stating the expected type here would prevent that. (And is why mandatory top level declarations are good -- they can prevent bugs caused by an unexpected type being inferred). This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Crash in Data.ByteString.Lazy.hPut
Ah, of course. Thanks. I removed the hPut and it runs smoothly. I had forgotten that haskell chooses the types dynamically. Shouldn't haskell pick up that there is no 'mod' for Word8? I mean, shouldn't I get a nicer error message? Don Stewart wrote: jamie.love: Hi there, Not sure where to raise bugs in hackage libraries, so I'm posting here. If there is a better place, please let me know. The following code crashes with a divide by zero error when using the package 'binary-0.4.' Oh, hehe. \x - x `mod` 256 doesn't work if x :: Word8 That's your bug :) -- Don This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Crash in Data.ByteString.Lazy.hPut
Just to clarify, I know it was my mistake, and so I'm not blaming Haskell or Ghc. The first few times you realise the compiler isn't a magic wand that stops you being silly are the hardest. Jamie Love wrote: Oh, I see I wasn't thinking through the code (and I'm still in the honeymoon phase with Haskell, thinking it can do no wrong). Don Stewart wrote: jamie.love: Ah, of course. Thanks. I removed the hPut and it runs smoothly. I had forgotten that haskell chooses the types dynamically. Shouldn't haskell pick up that there is no 'mod' for Word8? I mean, shouldn't I get a nicer error message? Well, it inferred Word8 for your generated values, so 256 overflowed to 0. Stating the expected type here would prevent that. (And is why mandatory top level declarations are good -- they can prevent bugs caused by an unexpected type being inferred). This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Crash in Data.ByteString.Lazy.hPut
I should point out that this is on GHC 6.8.2 compiled from source on a Mac powerpc. Jamie Love wrote: Hi there, Not sure where to raise bugs in hackage libraries, so I'm posting here. If there is a better place, please let me know. The following code crashes with a divide by zero error when using the package 'binary-0.4.' module Main where import IO import Data.Binary import Data.Binary.Put import qualified Data.ByteString.Lazy as B simpleImage = take tot (map (\x - x `mod` 256) [1..]) where tot = 640 * 480 main = do output - openFile test.tmp WriteMode B.hPut output $ runPut $ mapM_ putWord8 simpleImage -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Binary IO of a list of ints
Hi there I have a list of ints, with values between 0 and 255 and I need to print them out in little endian form to a file. I've been using Data.Binary for single values, e.g. runPut $ do put 'B' put (0 :: Int32) I'm wondering how I can go about writing a list of Ints out. My thought was to do something like: foldr (\x B.hPut output (runPut $ do put (x :: Word8))) data (where output is my file handle), but apart from giving me type errors, it seems a rather arduous way to do it. Could anyone suggest a better way to do this? -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Binary IO of a list of ints
Stephan Walter wrote: Hi, On 2008-01-24 12:14, Jamie Love wrote: I have a list of ints, with values between 0 and 255 and I need to print them out in little endian form to a file. How about just using Data.Char.chr ? Essentially because I need to control the byte ordering, and it has to be in the current case the opposite to my computer's native ordering (the file is a binary file). Prelude let a = [32..64] :: [Int] Prelude map Data.Char.chr a !\#$%'()*+,-./0123456789:;=?@ --Stephan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Binary IO of a list of ints
Thanks Jed, That works (or at least it's taking ages to error :-) ) Jed Brown wrote: On 24 Jan 2008, [EMAIL PROTECTED] wrote: Hi there I have a list of ints, with values between 0 and 255 and I need to print them out in little endian form to a file. I've been using Data.Binary for single values, e.g. runPut $ do put 'B' put (0 :: Int32) This will be big endian by default. If it needs to be little endian, use Data.Binary.Put.putWord32le and relatives. With a list, you could do something like: runPut $ mapM_ (putWord32le . fromIntegral) listOfInts I hope this helps. Jed -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Basic binary IO
Ah, thanks Don, Brandon, I looked at this but neglected to read through and understand the example enough. Thanks for the tips, they're a great help. Don Stewart wrote: jamie.love: bmpHeader = runPut $ do put 'B' put 'M' put (0 :: Int32) put (0 :: Int32) put (14 :: Int32) Yields the lazy bytestring, BM\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\SO -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Basic binary IO
Hello all, I'm wondering if anyone has a reference to any binary IO and data conversion tutorials. I'm playing around with generating a BMP file in haskell, and am a little stuck on the best way to go about the simple task of creating the BMP header. The header is BM + 4 bytes for file size + 4 bytes reserved + 4 bytes for offset where data begins. I have the basis starting off at: bmpHeader = B.pack $ [ 0x42, 0x4D ] ++ [0 , 0, 0, 0] ++ [0 , 0, 0, 0] ++ [14 :: Int32] (where B is Data.ByteString) I'm wondering how I can: 1/ convert a 32 bit number (Int32, Char32) to 4 Char8 elements 2/ rotate bits/bytes in a 32 bit Char32 (or Int32) so they are explicitly little-endian (I work on a mac powerbook, and it is big-endian) 3/ convert an Integer or Int type to an Int32 type Any pointers or suggestions would be helpful. Thanks -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
