May 2010 - Haskell-Cafe

Cabal-install: bus error
by Chris Eidhof 04 May '10

04 May '10

Hey everyone, After I upgraded to a newer cabal-install my cabal-install broke again: I get a Bus Error when doing "cabal update" or "cabal install something". The version that was bundled with the Haskell platform worked fine, but now it's broken again. I'm not sure what it was that went wrong or how to debug this. The previous time I had Bus Errors I upgraded to the newest available Haskell Platform release and started from scratch. I would prefer not to do that again. However, I don't really know how to solve the Bus Error. Does anyone have a clue where to start? Or is there a way to undo my cabal-install upgrade? -chris

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gtk2hs for 2010.1.0.0
by Maciej Piechotka 03 May '10

03 May '10

Does anyone have installer for gtk2hs for Haskell Platform 2010.1.0.0? Regards

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Re: Haskell and scripting
by Pierre-Etienne Meunier 03 May '10

03 May '10

Hi, You do not need a DSL at all, in fact. The simplest way to do this, if you use GHC, is to use the GHC api. This can compile everything for you, and return a value with type "Dynamic", from Data.Dynamic and Data.Typeable. It is type-safe, you can write within very little time (even if the documentation for the GHC api is not -- yet -- perfect), and use a real language whose users are still alive. Cheers, PE ps : by the way, if you are interested by this kind of programming, I saw that someone was writing a shell in haskell, called hashell I think. If you want to help him... > Hello Café, > > I don't know if you know > conky<http://en.wikipedia.org/wiki/Conky_%28software%29>. > It's a well-known open-source system monitor (a software that displays > information on the desktop, like CPU frequency, disk usage, network rate, > etc.). > It is quite good, but it's very descriptive, and even if you can call shell > commands it's clearly not made for being scripted. > What I would do is to make a similar system monitor, which base would be > compiled Haskell code, but that would be scriptable with some DSL, or > already existing interpreted language. > I've thought about a Lisp/Scheme language, since those languages are > functional, dynamically typed and simple (so enable a quick scripting) and > I'm not very keen on making my own DSL > > What I would like to know is: > 1) If you have other solutions > 2) How do haskellers usually script their applications

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eclipse, haskell-platform and windows. Installation problem.
by Han Joosten 03 May '10

03 May '10

Hi all I have been using an old version of eclipsepf for quite some time now on my windows machine. Recently I saw that there is a newer version, as well as a newer version of haskell. However, I am not able to get it all to work. I wonder if you are able to help me out. First, I installed the newest version of ghc by means of the haskell-platform. Then I installed git, so I was able to download the special variant of scion, as specified at http://sourceforge.net/projects/eclipsefp/files/EclipseFP%202%20branch/1.11… Then I tried to build the downloaded scion: C:\data\gitRepository\scion>runhaskell Setup.hs configure Configuring scion-0.1.0.2... Setup.hs: At least the following dependencies are missing: binary ==0.5.*, ghc-paths ==0.1.*, ghc-syb ==0.1.*, hslogger ==1.0.*, json ==0.4.*, list-tries ==0.1.*, multiset >=0.1 && <0.3, uniplate ==1.2.* As you can see, this failed. However, since I have the new cabal, that comes with the haskell platform, I figured that the above dependancies should not be a problem. So I used cabal: Cabal install binary (and then I cabal installed all other missing packages. ) All cabal install commands completed succesfully. Then, again i tried 'runhaskell setup.hs configure', but this failed again with exactly the same message as before. It seems that all packages that I installed dissapeared! I probably do something stupid, but I cannot figure out what I should do. Any help is welcome! Thanks! Han Joosten -- View this message in context: http://old.nabble.com/eclipse%2C-haskell-platform-and-windows.-Installation… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Release: rangemin-2.0
by Louis Wasserman 03 May '10

03 May '10

The original rangemin project was my first Haskell package, and definitely my first attempt at super-advanced algorithms work in Haskell. (I here define "super-advanced" as "not in MIT OpenCourseWare undergraduate algorithms lecture notes from any year.") Here's the problem: Suppose we have an array of length n. Preprocess the array in O(n) time such that we can look up the minimum element of any slice in the array in O(1) time. Coming back to this project after two years, and especially rewriting the approach with the vector package, was *spectacularly* fun. rangemin-2.0<http://hackage.haskell.org/package/rangemin>is now on Hackage, with a new API as well. The constant factor on the O(n) preprocessing is, based on criterion benchmarks, 88 milliseconds per million elements, on my 2.5GHz Ubuntu laptop, with GHC HEAD and -O2 -fvia-c -optc-O3. I've spent the past three days unsuccessfully trying to get the LLVM backend to work, because this algorithm has a *lot* of the sort of tight loops that LLVM excels at. Unfortunately, I haven't been able to install the LLVM backend, which is very disappointing. That said, GHC with the C backend is about 10x slower than an optimized C++ implementation, which is all right considering that the algorithm plays so much to C++'s strengths. (If anybody has LLVM working and would be willing to help, I'd massively appreciate it if you could benchmark both the C++ implementation -- not mine, but included in a tarball inside the rangemin distribution package -- and my implementation, with LLVM -O2. Benchmarking code is here<http://hpaste.org/fastcgi/hpaste.fcgi/view?id=25309#a25309> .) Louis Wasserman wasserman.louis(a)gmail.com http://profiles.google.com/wasserman.louis

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Building regex-posix for windows
by Станислав Черничкин 03 May '10

03 May '10

I'm having trouble building regex-posix for Windows under MinGW because MinGW does not include regex.h. As far as I know Haskell Platform uses MinGW and it includes regex-posix. I'd like to build regex-posix by myself, like Haskell Platform does. I would appreciate it if someone suggests some resources about building regex-posix and other packages for windows. I’m also looking for Haskell Platform developer’s blog or something similar, where I can read about porting Haskell on Windows. Thanks.

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Learning about Programming Languages (specifically Haskell)
by Samuel Williams 03 May '10

03 May '10

Dear Friends, I'm looking for some help from the Haskell community. I hope this is the right place to ask for information. I'm putting together a website aimed at high school students and teachers, and would like to add a few paragraphs to the following page: http://programming.dojo.net.nz/languages/haskell/index ... explaining why one would want to learn Haskell. I don't know the answer to this since I don't use Haskell extensively. What are the main application areas and how is it useful? Any other suggestions or ideas for the Haskell page would be fantastic, and any suggestions to other pages in general is also very helpful. http://programming.dojo.net.nz/ Kind regards, Samuel

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Re: FRP for game programming / artifical life simulation
by Ben 03 May '10

03 May '10

slightly off topic, but how does one handle pausing / saving / restarting in the FRP framework, especially the arrowized version? i've only been able to do this via explicit (or monadic) state-passing, e.g. imperative / piecemeal versus declarative / wholemeal, which seems against the spirit of FRP. b

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MonadPlus or Alternative or ...?
by Sean Leather 03 May '10

03 May '10

I want to generalize a set of functions from lists to some functor type. I require the following three operation types. f a a -> f a f a -> f a -> f a Should I choose MonadPlus and use these? mzero return mplus Or should I choose Alternative and use these? empty pure (<|>) Or should I make my own class? Or is there another option? Thanks, Sean

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FRP for game programming / artifical life simulation
by Ben Christy 03 May '10

03 May '10

I have an interest in both game programming and artificial life. I have recently stumbled on Haskell and would like to take a stab at programming a simple game using FRP such as YAMPA or Reactive but I am stuck. I am not certain which one I should choose. It seems that Reactive is more active but is it suitable for game programming. Also has anyone attempted to implement neural networks using FRP if so again which of these two approaches to FRP would you suggest?

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