- Haskell-Cafe - Haskell.org

Haskell, OpenGL on Windows
by Mark Spezzano 17 Mar '09

17 Mar '09

Hi, Can someone PLEASE help me to understand exactly how to configure OpenGL on Window using Haskell. I'm using Eclipse IDE. When I try to run the file Test1.hs in GHCi then I get the following error: Loading package syb ... linking ... done. Loading package base-3.0.3.0 ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package containers-0.2.0.0 ... linking ... done. Loading package OpenGL-2.2.1.1 ... can't load .so/.DLL for: GL (addDLL: could not load DLL) Prelude Main> I've copied the GLUT dll into Windows/System32. Is there some flag or option that I need to enable to tell Haskell where to go to link in the library. What do I do with the other .h and .lib files from GLUT? Thanks Mark

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Re: [Haskell-cafe] Polynomial and VectorSpace
by Henning Thielemann 17 Mar '09

17 Mar '09

On Mon, 16 Mar 2009, Matthew Donadio wrote: > Thy polynomial and matrix libraries weren't really developed to be stand > alone libraries. I was developing some DSP libraries that required > polynomial and matrix math, so I implemented what I needed so I could test > the DSP. Both libraries work for lower orders, but I suspect they are buggy > with big inputs. My long term goal was to interface with LAPACK and/or GSL > for the numeric heavy lifting, but that never happened. > > The same goes for the FFT library. That was written in support of the DSP > libraries, and also as a learning exercise for me (to better understand > how/why the FFT works). FFTW was the long term goal. In the meantime fftw and gsl-matrix interfaces exist on Hackage.

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using Typeable with STRefs
by Michael Vanier 17 Mar '09

17 Mar '09

Hi, I'm having a problem using Typeable with STRefs. Basically, I want to store STRefs (among other things) in a universal type. STRef is an instance of Typeable2, which means that STRef s a is Typeable if s and a are both Typeable. The problem is that the state type s is opaque and I can see no way to make it Typeable (other than making it RealWorld, and I don't want to use IO for this). If this is the case, then AFAICT there is no point in having STRefs be instances of Typeable2. Am I missing something? Here's the code I'd like to write: import Data.Typeable import Data.STRef import Control.Monad.ST data Value = forall a . Typeable a => V a deriving Typeable getValue :: Typeable a => Value -> Maybe a getValue (V v) = cast v -- I need the Typeable s constraint for the code to compile, but I'd rather leave it out. test :: Typeable s => ST s Integer test = do ref <- newSTRef (10 :: Integer) let refVal = V ref case getValue refVal of Nothing -> error "BAD" Just r -> readSTRef r -- This doesn't compile, because s is not Typeable. test2 :: Integer test2 = runST test Thanks in advance, Mike

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darcs fundraising drive - only $720 left to go!
by Eric Kow 17 Mar '09

17 Mar '09

Hi everybody, Just a quick update on the fundraising drive. We are trying to raise $1000 to help pay for travel to the upcoming Haskell hackathon (the second of our biannual darcs hacking sprints). So far we have raised $280, so we're almost a third of the way there. Think you can help? Details on this page http://www.darcs.net/donations.html Many thanks! Eric PS. Ultimately, what we are trying to buy is *time*. So if you have a few spare moments in your week, the most generous donation you can make is by offering us a little of your time. Come join us in Utrecht, 17-19 April or on #darcs! Otherwise, we accept Paypal :-) -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9

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Re: [Haskell-cafe] Lambda-Cube 3D render engine
by Csaba Hruska 16 Mar '09

16 Mar '09

2009/3/16 Duane Johnson <duane.johnson(a)gmail.com> > Looks great! > By any chance, is the mesh loading functionality separate from the texture > loading? > Yes, it is completly separated from material, it only refers to material's name. You can define the material writing a nice human readable script: http://www.ogre3d.org/docs/manual/manual_14.html#SEC23 > > -- Duane Johnson > > On Mar 16, 2009, at 1:01 PM, Csaba Hruska wrote: > > Hi! > > I've created a wiki page for my project. > Currently only some text and screenshot are available. > Additional documentation and source code are coming soon.. :) > > http://www.haskell.org/haskellwiki/LambdaCubeEngine > > Cheers, > Csaba Hruska > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > >

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Polynomial and VectorSpace
by Peter Verswyvelen 16 Mar '09

16 Mar '09

The DSP package on Hackage seems to contain complex polynomial functions. It seems these functions are completely independent of the other DSP functions, so this package could be split of? Also, polynomials form a vector space, so could be made an instance of VectorSpace class?

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Lambda-Cube 3D render engine
by Csaba Hruska 16 Mar '09

16 Mar '09

Hi! I've created a wiki page for my project. Currently only some text and screenshot are available. Additional documentation and source code are coming soon.. :) http://www.haskell.org/haskellwiki/LambdaCubeEngine Cheers, Csaba Hruska

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Incompatibility of different (monad transformer) libraries
by ariep 16 Mar '09

16 Mar '09

Hi, ==== Problem instance ==== In my code, I use some monad transformers. I used to use the "mtl" package, but I recently switched to the combination "transformers"/"monads-tf" (mainly for the Applicative instances). The same code also uses the "haskeline" library, for line reading. Haskeline allows to edit the user's history (previously entered lines), but only through a Control.Monad.State interface, and that happens to be the Control.Monad.State from "mtl". So now, my package also needs to import "mtl". This combination of package dependencies gives import conflicts: whenever I import some Control.Monad.{State,Error,Cont,...} module, there is more than one package providing such a module. ==== Solution? ==== For now, I resolve the ambiguity by using "Package imports", i.e. annotate the ambiguous imports by the right package name. Is this the best solution? The ghc manual states, that the package import extension should not be necessary. I can think of another solution, by creating a dedicated package, which imports mtl:Control.Monad.* and re-exports them under another name, but that's even less elegant than package imports. What is the recommended way to deal with module name conflicts, such as this one? Regards, Arie BTW: how can I let the user edit a line of text, from a non-empty starting value for the text? (In other words, actually *edit* a line, not enter a new one.) I currently do this by adding the starting value to the user's history, so he/she can get it by pressing the up arrow key. This is clearly not optimal.

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Re: Has anybody replicated =~ s/../../ or even something more basic for doing replacements with pcre haskell regexen?
by Thomas Hartman 16 Mar '09

16 Mar '09

So, I tweaked Text.Regex to have the behavior I need. http://patch-tag.com/repo/haskell-learning/browse/regexStuff/pcreReplace.hs FWIW, the problem I was trying to solve was deleting single newlines but not strings of newlines in a document. Dead simple for pcre-regex with lookaround. But, I think, impossible with posix regex. -- replace single newlines, but not strings of newlines (requires pcre look-around (lookaround, lookahead, lookbehind, for googlebot)) http://perldoc.perl.org/perlre.html testPcre = ( subRegex (mkRegex "(?<!\n)\n(?!\n)") "asdf\n \n\n\nadsf" "" ) == "asdf \n\n\nadsf" Can I lobby for this to make its way into the Regex distribution? Really, I would argue that every regex flavor should have all the functions that Text.Regex get, not just posix. (subRegex is just the most important, to my mind) Otherwise I'll make my own RegexHelpers hackage package or something. Hard for me to see how to do this in an elegant way since the pcre packages are so polymorphic-manic. I'm sure there is a way though. Or if you point me to the darcs head of regex I'll patch that directly. 2009/3/14 Thomas Hartman <tphyahoo(a)gmail.com>: > Right, I'm just saying that a "subRegex" that worked on pcre regex > matches would be great for people used to perl regexen and unused to > posix -- even it only allowed a string replacement, and didn't have > all the bells and whistles of =~ s../../../ in perl. > > 2009/3/12 ChrisK <haskell(a)list.mightyreason.com> >> Thomas Hartman wrote: >>> >>> Is there something like subRegex... something like =~ s/.../.../ in >>> perl... for haskell pcre Regexen? >>> >>> I mean, subRegex from Text.Regex of course: >>> http://hackage.haskell.org/cgi-bin/hackage-scripts/package/regex-compat >>> >>> Thanks for any advice, >>> >>> thomas. >> >> Short answer: No. >> >> This is a FAQ. The usual answer to your follow up "Why not?" is that the >> design space is rather huge. Rather than justify this statement, I will >> point at the complicated module: >> >> http://hackage.haskell.org/packages/archive/split/0.1.1/doc/html/Data-List-… >> >> The above module is "a wide range of strategies for splitting lists", which >> is a much simpler problem than your subRegex request, and only works on >> lists. A subRegex library should also work on bytestrings (and Seq). >> >> At the cost of writing your own routine you get exactly what you want in a >> screen or less of code, see >> http://hackage.haskell.org/packages/archive/regex-compat/0.92/doc/html/src/… >> for "subRegex" which is 30 lines of code. >> >> Cheers, >> Chris >> >

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Visualising the Hierarchical Namespace
by Don Stewart 16 Mar '09

16 Mar '09

I've just finished a post (and quick tool) for graphing the complete module namespace of Haskell, taken from the core libraries and all of Hackage. It's quite large: http://donsbot.wordpress.com/2009/03/16/visualising-the-haskell-universe/

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