December 2008 - Haskell-Cafe

[Announce] TTTAS (with excuse for second attempt to post)
by S. Doaitse Swierstra 07 Dec '08

07 Dec '08

We are pleased to announce the availability of the package "TTTAS", which contains the code associated with our paper at the coming TLDI workshop: \@inproceedings{ BSV09, author = {Arthur Baars and S. Doaitse Swierstra and Marcos Viera}, title = {Typed Transformations of Typed Abstract Syntax}, booktitle = {TLDI '09: fourth ACM SIGPLAN Workshop on Types in Language Design and Implementation}, year = {2009}, location = {Savannah, Georgia, USA}, publisher = {ACM}, address = {New York, NY, USA}, } For more information see: http://www.cs.uu.nl/wiki/bin/view/Center/TTTAS Arthur Baars Marcos Viera Doaitse Swierstra

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Dr Dobbs: Time to get good at functional programming
by Tim Wawrzynczak 07 Dec '08

07 Dec '08

Amen to that. People who haven't really given a fair look at functional langauges (Haskell in particular) seem to have a very poor conception of them. Again, this seems to especially be a problem with Haskell (i.e., the whole "monads are hard" thing)... If this is where people are getting their information from, it would definitely behoove the Haskell community to update its image to further Haskell and FP in general :) On Sun, Dec 7, 2008 at 12:11 PM, Don Stewart <dons(a)galois.com> wrote: > jason.dusek: > > Too bad they didn't pimp Haskell as practical. > > It looked like an archaic view of Haskell based on reading wikipedia, > imo. Perhaps we should take charge of the wikipedia page, if it is that > influential. > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Data.Map.fromListWith
by Paul Johnson 07 Dec '08

07 Dec '08

I've just been looking at the Data.Map function "fromListWith". According to the docs, it has the type: * fromListWith* :: Ord <http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data-Ord.html#t%…> k => (a -> a -> a) -> [(k, a)] -> Map <http://www.haskell.org/ghc/docs/latest/html/libraries/containers/Data-Map.h…> k a I'd have thought that a better type would be * fromListWith* :: Ord <http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data-Ord.html#t%…> k => (a -> b -> b) -> [(k, a)] -> Map <http://www.haskell.org/ghc/docs/latest/html/libraries/containers/Data-Map.h…> k b This wouldn't break any existing code, but would allow things like "fromListWith (:)" to do the Right Thing. Would this be a sensible change (along with the other "with" functions in the module). Paul.

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SDL program under MinGW
by sam lee 07 Dec '08

07 Dec '08

Hi. I am using Windows Vista. I installed the following: - ghc 6.8.3 (using official Windows binary installer) - MinGW (from http://nuwen.net/mingw.html) - SDL binding (from http://hackage.haskell.org/cgi-bin/hackage-scripts/package/SDL) I am trying to compile the following program: module Main where import qualified Graphics.UI.SDL as SDL main = do SDL.init [SDL.InitEverything] SDL.quit I get the following error: C:\Users\client\code\sandbox>ghc --make Example.hs Linking Example.exe ... C:\MinGW\lib/libSDLmain.a(SDL_win32_main.o)(.text+0x409):SDL_win32_main.c: undefined reference to `SDL_main' According to SDL faq (http://www.libsdl.org/faq.php?action=listentries&category=4#48) I should use "int main(int argc, char *argv[])", not "int main()" nor "WinMain()". Can anyone compile the above snippet on windows machine? I am using SDL library that is shipped with MinGW distribution that I'm using. I also recompiled SDL haskell binding with official SDL windows binary (http://www.libsdl.org/release/SDL-devel-1.2.13-mingw32.tar.gz) But I get the same undefined reference to SDL_main linker error. Do I need to have specific main IO action so that SDL would work in Haskell? Thank you. Sam.

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pbkdf2 on hackage Re: Re[2]: [Haskell-cafe] Password hashing
by Thomas Hartman 07 Dec '08

07 Dec '08

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/PBKDF2 Since no one took up my code review request I just did the best I could and uploaded to hackage. There were indeed some mistakes in my initial post, fixed now. (Code review is still wished, though!) Alas, documentation doesn't build with hackage, altough it does for me locally. (Seems like almost everything I do these days -- what am I doing wrong?!) Also I'm open to folding this into a more established crypto package if there are any takers... psst, dominic. Also, dominic, shouldn't your crypto package be added to category Cryptography (a cabal file change) so it lists aside the other crypto packages? thanks, thomas. 2008/11/26 Thomas Hartman <tphyahoo(a)gmail.com>: > Sorry about the hideous formatting above. Reattached as a text file. > > t. > > 2008/11/26 Thomas Hartman <tphyahoo(a)gmail.com>: >> OK, I went ahead and implemented pbkdf2, following the algorithm >> linked to by bulat and Michael. >> >> If there are any crypto gurus who can code-review this I would be much >> obliged, and when I'm confident enough that this does the right thing >> I'll put it up on hackage. >> >> I don't do much crypto so this *definitely* needs a review before it >> becomes a library? >> >> How's this looks, cafe? >> >> Thanks! >> >> Thomas. >> >> >> {-# LANGUAGE ScopedTypeVariables #-} >> module Crypto.PBKDF2 (pbkdf2, pbkdf2') where >> >> import qualified Data.ByteString.Char8 as B >> import qualified Data.ByteString.Lazy as L >> import GHC.Word >> import Control.Monad (foldM) >> import Random >> import Data.Digest.SHA512 (hash) >> import Data.Word >> import Data.Bits >> import Data.Binary >> >> newtype Password = Password [Word8] >> newtype Salt = Salt [Word8] >> newtype HashedPass = HashedPass [Word8] >> deriving Show >> {- | A reasonable default for rsa pbkdf2? Actually I'm not really >> sure, ask folk with more experience. >> >>> pbkdf2 = pbkdf2' prfSHA512 512 512 512 >> -} >> t = pbkdf2 ( Password . toWord8s $ "meh" ) ( Salt . toWord8s $ "moo" ) >> pbkdf2 :: Password -> Salt -> HashedPass >> pbkdf2 = pbkdf2' prfSHA512 512 512 512 >> >> {- | Password Based Key Derivation Function, from RSA labs. >> >>> pbkdf2' prf hlen cIters dklen (Password pass) (Salt salt) >> -} >> pbkdf2' :: ([Word8] -> [Word8] -> [Word8]) -> Integer -> Integer -> >> Integer -> Password -> Salt -> HashedPass >> pbkdf2' prf hlen cIters dklen (Password pass) (Salt salt) >> | dklen > ( (2^32-1) * hlen) = error $ "pbkdf2, (dklen,hlen) : " ++ >> (show (dklen,hlen)) >> | otherwise = >> let --l,r :: Int >> l = ceiling $ (fromIntegral dklen) / (fromIntegral hlen ) >> r = dklen - ( (l-1) * hlen) >> ustream :: [Word8] -> [Word8] -> [[Word8]] >> ustream p s = let x = prf p s >> in x : ustream p x >> --us :: Integer -> [[Word8]] >> us i = take (fromIntegral cIters) $ ustream pass ( salt `myor` >> ((intToFourWord8s i) )) >> --f :: [Word8] -> [Word8] -> Integer -> Integer -> [Word8] >> f pass salt cIters i = foldr1 myxor $ us i >> ts :: [[Word8]] >> ts = map (f pass salt cIters) ( [1..l] ) >> in HashedPass . take (fromIntegral dklen) . concat $ ts >> >> -- The spec says >> -- Here, INT (i) is a four-octet encoding of the integer i, most >> significant octet first. >> -- I'm reading from the right... is this the right thing? >> toWord8s x = L.unpack . encode $ x >> >> --intToFourWord8s :: Integer -> [Word8] >> intToFourWord8s i = let w8s = toWord8s $ i >> in drop (length w8s -4) w8s >> >> myxor :: [Word8] -> [Word8] -> [Word8] >> myxor = zipWith xor >> >> myor :: [Word8] -> [Word8] -> [Word8] >> myor = zipWith (.|.) >> >> prfSHA512 :: [Word8] -> [Word8] -> [Word8] >> prfSHA512 x y = hash $ x ++ y >> >> >> 2008/11/26 John Meacham <john(a)repetae.net>: >>> What you are using there is not a salt, but rather a secret key. The >>> important thing about a salt is that it is different for _every user_. >>> and you actually store the salt unhashed along with the hash. (it is not >>> secret information). A salt protects against a dictionary attack, for >>> instance, you might have a dictionary of hash's and the common passwords >>> they go to but if you add a 32 bit salt, you would need 2^32 entries for >>> each dictionary word, making such an attack unworkable. You can also >>> trivially tell if two users have the _same_ password just by comparing >>> the hashes without a salt. >>> >>> John >>> >>> -- >>> John Meacham - ⑆repetae.net⑆john⑈ >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe(a)haskell.org >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >> >

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Trouble installing ghc-6.10.1 on linux
by Bit Connor 06 Dec '08

06 Dec '08

I'm trying to install ghc 6.10.1 on a machine with the crux distro. libc version 2.3.6 gcc 4.0.3 linux version 2.6.15.6 First I tried the binary version ghc-6.10.1-i386-unknown-linux.tar.bz2 and I very quickly get this error: $ ./configure checking build system type... i686-pc-linux-gnu checking host system type... i686-pc-linux-gnu checking target system type... i686-pc-linux-gnu Which we'll further canonicalise into: i386-unknown-linux checking for path to top of build tree... configure: error: cannot determine current directory $ Next I tried building the source version ghc-6.10.1-src.tar.bz2 using ghc 6.6 that is already installed. configure works but make eventually dies with: ... Configuring ghc-6.10.1... cabal-bin: At least the following dependencies are missing: Cabal -any, base <3, filepath >=1 && <1.2, haskell98 -any, hpc -any, template-haskell -any, unix -any make[2]: *** [boot.stage.2] Error 1 Any ideas? Thanks, Bit

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latest Hood ?
by Simon Michael 06 Dec '08

06 Dec '08

Hugo Pacheco wrote: > The library also features the visualization of the intermediate data > structure of hylomorphisms with GHood. I hadn't come across GHood and Hood before, and they look quite a useful addition to the toolbox. http://www.haskell.org/hood says "The current released version of HOOD is the July 2000 release, but there is also a patch to all HOOD to work with GHC 5.00.". The Observe.lhs there doesn't immediately work with current GHC. Has anyone got an updated version, or is this available in some more recent library or package ? Or, I may have misunderstood, and Debug.Trace may do everything that Hood did. Still, a working Hood would be useful to get the nice visualisations of GHood. Thanks - Simon

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Can't cabal install readline
by Martijn van Steenbergen 06 Dec '08

06 Dec '08

Hello, This week I upgraded to GHC 6.10 using the .pkg installer. It installed without a single hiccup -- thanks! I've noticed two odd things: the standard library haddock that comes with the installer doesn't have links to the hs-coloured sources anymore (and neither does the online documentation); I miss that a lot. I also can't Ctrl+R anymore in GHCi to search my command history. But I can learn to live without those. Another minor inconvenience is that the packages I had installed (using cabal) are no longer available to GHC -- I think I will have to reinstall them. But I cannot continue working on my Yogurt project anymore, because it depends on readline, which fails to build: <snip> checking for rl_readline_version... yes checking for rl_begin_undo_group... no configure: error: readline not found, so this package cannot be built See `config.log' for more details. cabal: Error: some packages failed to install: Yogurt-0.2 depends on readline-1.0.1.0 which failed to install. readline-1.0.1.0 failed during the configure step. The exception was: exit: ExitFailure 1 The build failure mentions config.log which I cannot find anywhere on my system. I have readline installed using MacPorts without problems, and the cabal package worked fine too on the previous version of GHC. I'm on Intel Leopard. How can I get cabal install readline to succeed on the new GHC? Thanks much, Martijn.

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Haskell Weekly News: Issue 96 - December 6, 2008
by Brent Yorgey 06 Dec '08

06 Dec '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20081206 Issue 96 - December 06, 2008 --------------------------------------------------------------------------- Welcome to issue 96 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements Haskell haikus. Gwern Branwen [2]announced that he has collected all known haikus about Haskell and put them on a [3]wiki page. Add more! Platforms that GHC supports. Simon Peyton-Jones [4]linked to a [5]new page clearly articulating what platforms GHC supports, and what platforms its maintainers would like it to support. If you're interested and willing to help sponsor a "Tier 2" platform, let them know! Using Data Parallel Haskell. Manuel Chakravarty [6]announced a new [7]wiki page with documentation for Data Parallel Haskell. DrHylo 0.0.1. Hugo Pacheco [8]announced the [9]release of [10]DrHylo, a tool for deriving hylomorphisms from a restricted Haskell syntax. It is based on the algorithm first presented in the paper Deriving Structural Hylomorphisms From Recursive Definitions at ICFP'96 by Hu, Iwasaki, and Takeichi. The generated code can be run with [11]Pointless Haskell, allowing the visualization of the recursion trees of Haskell functions. pointless-haskell 0.0.1. Hugo Pacheco [12]announced the [13]release of [14]Pointless Haskell, a library for point-free programming with recursion patterns defined as hylomorphisms, inspired in ideas from the PolyP library. The re-implementation of the library using type functions (in opposition to classes with functional dependencies) enables a type-level view of data types as the fixed points of functors and provides a better experience to the users in terms of code sanity. The library also features the visualization of the intermediate data structure of hylomorphisms with GHood. Projects that depend on the vty package?. Corey O'Connor [15]asked whether there are any other projects that depend on the [16]vty package. If so, let him know! The package also has a new [17]trac and wiki. haskell-src-exts 0.4.4. Niklas Broberg [18]announced the release of [19]haskell-src-exts 0.4.4, which adds support for pragmas. ChristmasTree 0.1. S. Doaitse Swierstra [20]announced the release of the [21]ChristmasTree package, which stands for "Changing Haskell's Read Implementation Such That by Manipulating Abstract Syntax Trees it Reads Expressions Efficiently". TTTAS. S. Doaitse Swierstra [22]announced the release of [23]TTTAS, a library for typed transformations of typed abstract syntax. GHood. Hugo Pacheco [24]announced that GHood, a graphical backend for the lightweight Hood Haskell debugger, has now been [25]released as a Cabal package. Discussion Animated line art. Andrew Coppin [26]asked for ideas on writing Haskell to generate some animations. Jobs Scala job in Boston writing quantitative finance software. Paul Chiusano [27]announced that [28]ClariFI is looking to hire developers with a strong background in functional programming to do a mixture of Scala and Java programming. ClariFI is a small company (about 15 developers) that specializes in software for quantitative investment management. This position is for the Boston office. If you're interested, send him an email. Blog noise [29]Haskell news from the [30]blogosphere. * Bryan O'Sullivan: [31]Functional programmers on Twitter. * Conal Elliott: [32]Sequences, segments, and signals. * >>> Gianfranco Alongi: [33]QuickCheck(ing) the code i C. * Edward Kmett: [34]The Pointed-Set Comonad. * Twan van Laarhoven: [35]Knight in n, part 3: rings. * "The GHC Team": [36]Explicit Stack Traces. * Real-World Haskell: [37]The Real World Haskell Book Club. * Real-World Haskell: [38]Real World Haskell: Now in Brazil. * >>> Matt Hellige: [39]Pointless fun. * Chung-chieh Shan: [40]The pointed-set monad. * Holumbus: [41]Status Update. * Paul R Brown: [42].editrc Tidbit for ghci. * Roman Cheplyaka: [43]DPH docs and project status. * David Sankel: [44]Introducing Reactive: Behaviors. * Manuel M T Chakravarty: [45]How to use Data Parallel Haskell.. * Conal Elliott: [46]Prettier functions for wrapping and wrapping. * Twan van Laarhoven: [47]Knight in n, part 2: combinatorics. * Yi: [48]Prototypes: Encoding OO-style inheritance in Haskell. * "Osfameron": [49]Functional Pe(a)rls v2 (now with Monads!) at the London Perl Workshop 2008. * Conal Elliott: [50]Sequences, streams, and segments. * Conal Elliott: [51]Early inspirations and new directions in functional reactive programming. * Clemens Fruhwirth: [52]XMonad GridSelect. About the Haskell Weekly News New editions are posted to [53]the Haskell mailing list as well as to [54]the Haskell Sequence and [55]Planet Haskell. [56]RSS is also available, and headlines appear on [57]haskell.org. To help create new editions of this newsletter, please see the information on [58]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [59]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://www.haskell.org//pipermail/haskell-cafe/2008-December/051529.html 3. http://haskell.org/haskellwiki/Haiku 4. http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/15958 5. http://hackage.haskell.org/trac/ghc/wiki/Platforms 6. http://www.haskell.org//pipermail/glasgow-haskell-users/2008-December/01627… 7. http://haskell.org/haskellwiki/GHC/Data_Parallel_Haskell 8. http://article.gmane.org/gmane.comp.lang.haskell.general/16668 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/DrHylo 10. http://haskell.di.uminho.pt/wiki/DrHylo 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pointless-haskell 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/48598 13. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pointless-haskell 14. http://haskell.di.uminho.pt/wiki/Pointless+Haskell 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/48471 16. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/vty 17. http://trac.haskell.org/vty/ 18. http://www.haskell.org//pipermail/haskell-cafe/2008-December/051444.html 19. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/haskell-src-exts… 20. http://www.haskell.org//pipermail/haskell/2008-December/020847.html 21. http://en.wikipedia.org/wiki/Sinterklaas 22. http://www.haskell.org//pipermail/haskell/2008-December/020848.html 23. http://www.cs.uu.nl/wiki/bin/view/Center/TTTAS 24. http://www.haskell.org//pipermail/haskell/2008-December/020849.html 25. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/GHood-0.0.2 26. http://www.haskell.org//pipermail/haskell-cafe/2008-December/051451.html 27. http://www.haskell.org//pipermail/haskell-cafe/2008-December/051295.html 28. http://clarifi.com/ 29. http://planet.haskell.org/ 30. http://haskell.org/haskellwiki/Blog_articles 31. http://www.serpentine.com/blog/2008/12/05/functional-programmers-on-twitter/ 32. http://conal.net/blog/posts/sequences-segments-and-signals/ 33. http://writert.blogspot.com/2008/12/quickchecking-code-i-c.html 34. http://comonad.com/reader/2008/the-pointed-set-comonad/ 35. http://twan.home.fmf.nl/blog/haskell/Knight3.details 36. http://ghcmutterings.wordpress.com/2008/12/04/explicit-stack-traces/ 37. http://www.realworldhaskell.org/blog/2008/12/03/the-real-world-haskell-book… 38. http://www.realworldhaskell.org/blog/2008/12/03/real-world-haskell-now-in-b… 39. http://matt.immute.net/content/pointless-fun 40. http://conway.rutgers.edu/~ccshan/wiki/blog/posts/Pointed_set/ 41. http://holumbus.fh-wedel.de/blog/?p=16 42. http://mult.ifario.us/p/editrc-tidbit-for-ghci 43. http://physics-dph.blogspot.com/2008/12/dph-docs-and-project-status.html 44. http://netsuperbrain.com/blog/posts/introducing-reactive-behaviors/ 45. http://justtesting.org/post/62610924 46. http://conal.net/blog/posts/prettier-functions-for-wrapping-and-wrapping/ 47. http://twan.home.fmf.nl/blog/haskell/Knight2.details 48. http://yi-editor.blogspot.com/2008/12/prototypes-encoding-oo-style.html 49. http://greenokapi.net/blog/2008/12/01/functional-pearls-v2-now-with-monads-… 50. http://conal.net/blog/posts/sequences-streams-and-segments/ 51. http://conal.net/blog/posts/early-inspirations-and-new-directions-in-functi… 52. http://blog.clemens.endorphin.org/2008/11/xmonad-gridselect.html 53. http://www.haskell.org/mailman/listinfo/haskell 54. http://sequence.complete.org/ 55. http://planet.haskell.org/ 56. http://sequence.complete.org/node/feed 57. http://haskell.org/ 58. http://haskell.org/haskellwiki/HWN 59. http://code.haskell.org/~byorgey/code/hwn/

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Fwd: problems with hs-plugins load-eval
by Alberto G. Corona 06 Dec '08

06 Dec '08

I have a web server which load server extensions. these extensions eval-uate configuration files that contains code (user-editable workflow descriptions). The problem is that I need common definitions for the extensions and for the configurration files. This is not permitted by ha-plugins. The minimal code example are the files below. main loads eval.hs , that evaluate a expression. The common definitions are in Include.hs. The error is: *GHCi runtime linker: fatal error: I found a duplicate definition for symbol Include_sum1_srt whilst processing object file /home/magocoal/haskell/devel/votesWorkflow/src/unused/tests/Include.o This could be caused by: * Loading two different object files which export the same symbol * Specifying the same object file twice on the GHCi command line * An incorrect `package.conf' entry, causing some object to be loaded twice. GHCi cannot safely continue in this situation. Exiting now. Sorry. * ** Do you kno how to solve the problem while maintaining the functionality? -------Include.hs------- module Include where sum [x,y]= x+y ------Main.hs----- module Main where import Include import System.Plugins main= do s <-loadExec "eval.o" "mainc" print s loadExec:: String-> String->IO String loadExec file method = do mv <- load file ["."] [] method case mv of LoadSuccess mod v -> v :: IO String LoadFailure msg -> return $ concat msg ------------Eval.hs-------- module Eval(mainc) where import System.IO.Unsafe import System.Eval.Haskell mainc= do i <- unsafeEval_ "sum1 [1,2]" ["Include"] [] []["."] :: IO (Either [String] Int) return $ show i

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