- Haskell-Cafe - Haskell.org

AI Strike Force!
by Andrew Wagner 26 Mar '07

26 Mar '07

The time has come! Calling all Haskell programmers interested in AI! I've established a new home base at http://www.haskell.org/haskellwiki/AI . Functional programming has long been recognized as an excellent paradigm for Artificial Intelligence. It's time to make Haskell an important language in that area! The goal is to provide a toolkit of AI tools in Haskell that can easily be applied to a wide variety of applications: e.g., Neural Networks, genetic algorithms, natural language processing tools, etc.

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Link error in ALUT "Hello, World"
by Nobuhito Mori 25 Mar '07

25 Mar '07

Hi, I installed OpenAL and ALUT bindings downloaded from http://hackage.haskell.org/packages/archive/pkg-list.html and tried compilation of "HelloWorld.hs" example which I got from http://darcs.haskell.org/packages/ALUT/ But it returns errors as follow and I can not get an '.exe' file. Though there are clearly "link errors", I can not understand why it happens. By option "-package ALUT", libalut.a (which made by pexports and dlltool because I do not know original "alut.lib" can be used by mingw) and other necessary libraries are automatically linked, I think. What is "@8" of "alutInit@8"? How can I avoid these errors? My environment is Windows XP SP2, GHC6.6, MinGW/MSYS (so some of mingw tools are duplicated. one is GHC's, the other is MinGW's) --------------- >ghc -package ALUT HelloWorld.hs C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x18): undefined reference to `alutInit@8' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xdc): undefined reference to `alutInitWithoutContext@8' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x19d): undefined reference to `alutExit@0' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x1d9): undefined reference to `alutGetError@0' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x210): undefined reference to `alutCreateBufferFromFile@4' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x2b0): undefined reference to `alutCreateBufferFromFileImage@8' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x36d): undefined reference to `alutCreateBufferHelloWorld@0' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x3f7): undefined reference to `alutCreateBufferWaveform@16' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x584): undefined reference to `alutLoadMemoryFromFile@16' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x6b8): undefined reference to `alutLoadMemoryFromFileImage@20' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x7e8): undefined reference to `alutLoadMemoryHelloWorld@12' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0x92f): undefined reference to `alutLoadMemoryWaveform@28' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xb2c): undefined reference to `alutGetMIMETypes@4' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xbc9): undefined reference to `alutGetMajorVersion@0' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xc01): undefined reference to `alutGetMinorVersion@0' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xc55): undefined reference to `alutSleep@4' C:\Program Files\Haskell\ALUT-2.0\ghc-6.6/libHSALUT-2.0.a(Config.o):fake:(.text+ 0xd89): undefined reference to `alutGetErrorString@4' --------------------- -------------------- Nobuhito _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/

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Re: [Haskell-cafe] What ever happened to Haskell 98 as a "stable branch"?
by Andrzej Jaworski 25 Mar '07

25 Mar '07

>If you answer "because H98 is obsolete", then file this away as a >must-read after H' is released Ideas always originate in a single mind. Good ideas are only footnotes to the best idea that determine them. Now: a team of people with different views on the same thing can achieve their best decorating a Christmas Tree. Unless, it is Haskell;-) Regards, -Andrzej

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newbie "concatenating" monad question
by Leandro Penz 25 Mar '07

25 Mar '07

Hi I'm new here and this is my first mail to the list, so be gentle :) I have some functions that build big strings by calling other functions and appending the result, like buildStuff = func1 ++ func2 ++ func3 ++ func4 My idea is to have a monad with a concatenating >>, so that I can: bulidStuff = do func1 func2 func3 func4 I am thinking about using the writer monad, but I would still have to use "tell". The list monad is not an option either, as it does not concatenate. Is there a proper way of doing something like this (efficiently) ? Leandro Penz

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Application of iterate
by Logesh Pillay 25 Mar '07

25 Mar '07

Ordinarily I would not post to a list when I've got a program running. But I've found learning Haskell so tough (this is my 4th try in the last two years) that I feel I have to bore everyone with my first non-trivial program. It is Newton's method adapted to give the square root of a number. And all in just one line which I think is an amazing demonstration of the power of Haskell. And it took no more than a couple of minutes to write (directly to the screen too as opposed to the usual many paper drafts with C). It works too, correct to 13 decimal points on my GHC system It is :- my_sqrt t = last (take 20 (iterate (\n -> n/2 + t/(2 * n)) t)) It is a bit crude though. 20 iterations is a bit arbitrary. I don't suppose there is a easy way to iterate until the results stop changing.

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"runST $ return ()" /= "runST (return ())" ??
by Marc A. Ziegert 25 Mar '07

25 Mar '07

hi! i've just discovered this strange behaviour of existential quantifiers with runST: --- Prelude Control.Monad.ST> :t runST (return ()) runST (return ()) :: () Prelude Control.Monad.ST> :t runST $ (return ()) <interactive>:1:9: Couldn't match expected type `forall s. ST s a' against inferred type `m ()' In the second argument of `($)', namely `(return ())' Prelude Control.Monad.ST> --- the same with "id runST undefined". is this a bug or an unsolved problem? i'm not sure wheather it is a part of the wanted feature of runST's type definition. i did not find any discussions about this. can anyone enlighten me, please? - marc

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OpenGL and GLUT in GHC
by Ruben Zilibowitz 24 Mar '07

24 Mar '07

Hi, I'm experimenting using OpenGL and GLUT in Haskell using GHC. There are modules Graphics.Rendering.OpenGL and Graphics.UI.GLUT. I am using these. I've encountered a strange bug which I'm having trouble with. If I render a sphere and a plane, then the plane is facing the wrong way and is shaded on the wrong side. If however I only render the plane then it appears to be facing the right way and is shaded on the correct side. I have made the source file available as a download here: http://www.cse.unsw.edu.au/~rubenz/stuff/test.hs It can be built by running: ghc --make test.hs I am using ghc 6.6 There is a comment in the source file saying: "Commenting out the line below here causes the plane to be rendered facing towards the camera..." The bug can be seen by commenting out the line of code that follows and recompiling. If anyone can help me by explaining why I am getting this bug or how to fix it that would be great. I'd be very appreciative. Cheers, Ruben

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Performance Help
by Dominic Steinitz 24 Mar '07

24 Mar '07

I have re-written the sha1 code so that it is (hopefully) easy to see that it faithfully implements the algorithm (see http://www.itl.nist.gov/fipspubs/fip180-1.htm) Having got rid of the space leak, I have been trying to improve performance. Currently, the haskell code is 2 orders of magnitude slower than the sha1sum that ships with my linux. > dom@heisenberg:~/sha1/testdist/sha1> time ./perfTest perfTest > c7eae62ddabb653bb9ce4eb18fa8b94264f92a76 > Success > > real 0m2.152s > user 0m2.112s > sys 0m0.028s > dom@heisenberg:~/sha1/testdist/sha1> time sha1sum perfTest > c7eae62ddabb653bb9ce4eb18fa8b94264f92a76 perfTest > > real 0m0.057s > user 0m0.008s > sys 0m0.004s I've played around with profiling and doubled the performance of the haskell code but I'm nowhere near the C performance. > Sun Mar 11 19:32 2007 Time and Allocation Profiling Report (Final) > > perfTest +RTS -p -RTS eg > > total time = 6.75 secs (135 ticks @ 50 ms) > total alloc = 1,483,413,752 bytes (excludes profiling overheads) > > COST CENTRE MODULE %time %alloc > > oneBlock Data.Digest.SHA1 39.3 40.1 > $& Data.Digest.SHA1 20.7 21.6 > f Data.Digest.SHA1 13.3 6.2 > getWord32s Data.Digest.SHA1 7.4 6.6 > test2 Main 5.9 8.7 > blockWord8sIn32 Data.Digest.SHA1 5.2 5.3 > blockWord8sIn512 Data.Digest.SHA1 3.0 4.4 > pad Data.Digest.SHA1 1.5 3.5 > k Data.Digest.SHA1 1.5 0.0 > fromBytes Data.Digest.SHA1 0.0 3.5 Here's the code that is taking the majority of the time. > ($&) :: [Word32] -> [Word32] -> [Word32] > a $& b = zipWith (+) a b > > -- Word128 -> Word512 -> Word128 > oneBlock ss xs = Word128 (as!!80) (bs!!80) (cs!!80) (ds!!80) (es!!80) > where > ws = xs ++ map (rotL 1) (zipWith4 xxxor wm3s wm8s wm14s ws) > where > xxxor a b c d = a `xor` b `xor` c `xor` d > wm3s = drop (16-3) ws > wm8s = drop (16-8) ws > wm14s = drop (16-14) ws > as = ai:ts > bs = bi:as > cs = ci:(map (rotL 30) bs) > ds = di:cs > es = ei:ds > ts = (map (rotL 5) as) $& (zipWith4 f [0..] bs cs ds) $& es $& (map k > [0..]) $& ws > Word128 ai bi ci di ei = ss Any help would be appreciated. I've put a copy of a working system here if anyone wants to experiment (http://www.haskell.org/crypto/downloads/sha1.tar.gz) Thanks, Dominic.

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Rank-2-polymorphism problem
by Martin Huschenbett 24 Mar '07

24 Mar '07

Hi, I'm writing some database code using HSQL and had to stop on a problem with rank-2-polymorphism that I can't solve. The essence of my code is: module Value where import Data.Maybe class SqlBind a where fromSqlValue :: String -> a data Field data Value emptyValue :: Field -> Value emptyValue _ = ... readValue :: Field -> (forall s. SqlBind s => s) -> Value readValue _ = ... That works just fine. But now I want a version of readValue that has a Maybe wrapped around the second parameter and that shall call readValue in the case of a Just and emptyValue in the case of Nothing. But I can't figure out how to write this function as I always get compiler errors. My trials were: -- The type I want to get. readValue' :: Field -> (forall s. SqlBind s => Maybe s) -> Value -- First trial: readValue' fld s = if isJust s then readValue fld (fromJust s) else emptyValue fld -- Second trial: readValue' fld s | isJust s = readValue fld (fromJust s) | otherwise = emptyValue fld -- Third trial: readValue' fld (Just s) = readValue fld s readValue' fld Nothing = emptyValue fld -- Fourth trial: readValue fld s = case s of Just s' -> readValue fld s' Nothing -> emptyValue fld But none of these trials worked. Is there any solution that works with GHC-6.6 for now? Thanks in advance, Martin.

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Re: Bouncing ball in Gtk2Hs
by Duncan Coutts 24 Mar '07

24 Mar '07

On Fri, 2007-03-23 at 20:24 +0300, Thach Si Lam wrote: > I'm trying to write Bouncing Ball demo in Gtk2hs. But i coudn't find > timer class (like in wxhaskell demo) in Gtk2hs. There is timeoutAdd: http://haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.10/System-Glib-MainLoop.html… used like so: timeoutAdd action 1000 where action is an action with type IO Bool and the number is the time to wait in milliseconds, (ie 1000 is 1 second). If the action returns True then it will get called again at the next timeout, otherwise it will not be called again. > How to deal with it ? In fact i have 2 processes: p1 for computing > some variables and p2 for changing (applying those variables) in > canvas. How to let them communicate together and update to canvas ? > Please, help me. Thank you very much. I'm forwarding this to the Haskell Cafe mailing list where someone might be able to give you a pointer. Duncan

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