- Haskell-Cafe - Haskell.org

[issue1002] darcs support for ohloh: call for help
by Simon Michael 08 Nov '10

08 Nov '10

Many of us are interested, and Ohloh is interested, in getting ohloh.net to support darcs repositories directly. It doesn't look hard to get good-enough support working; it just requires hacking 10 or so simple, well-organised ruby files. I've made a start on github[1], and set up a collaborative how-to & notes page here: http://etherpad.osuosl.org/pCIn3uhOeW Please help! And forward this to appropriate places. Best, -Simon [1] will be merged with prior work as needed

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Haskell meeting in Berlin on Tuesday Nov 9th
by Daniel van den Eijkel 08 Nov '10

08 Nov '10

Hi everybody, just wanted to send this again to the list - it's tomorrow. Cheers Daniel Am 10/31/10 6:30 PM, schrieb Sönke Hahn: > I can confirm the next meeting: > > Date: Tuesday, November 9th > Time: from 20:00 > Location: c-base, Rungestrasse 20, 10179 Berlin > > I was asked by some people from c-base, if we could do a talk about Haskell > for non-haskellers, which is a good idea, IMHO. We could discuss the details > in the mext meeting. > > Sönke >

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ANN: cil-0.1.0
by Tom Hawkins 08 Nov '10

08 Nov '10

CIL (C Intermediate Language) [1], not to be confused with the Common Intermediate Language, is a mature OCaml library that parses and reduces C programs down to a simplified subset of the C language, making it easier to analyze and compile C programs. This library [2, 3] parses these results, providing a Haskell interface to CIL. -Tom [1] http://cil.sourceforge.net/ [2] http://hackage.haskell.org/package/cil [3] http://github.com/tomahawkins/cil

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ANN: Copilot 0.25
by Lee Pike 08 Nov '10

08 Nov '10

Copilot[1] is a dataflow stream language built on Atom[2] for writing hard real-time C monitors of embedded systems. Copilot is a Haskell eDSL. The current release includes the following improvements: * Added true & false Specs (Spec Bool). * Removed generic const -- unneeded, since Spec is an instance of Num. * Change casting to only allow casts that (1) are guaranteed not to change the sign and (2) are to a larger type. * Added triggers---C functions to call when a monitor fails. * Removed libs from Copilot.hs. You must import these explicitly. * Fixed bugs with LTL and ptLTL libraries & examples and added documentation. * Added external arrays for sampling. * Fixed a bug in external array analysis for computing the minimum period size. * Added the ability to specify a HW clock for Atom. [1] <http://hackage.haskell.org/package/copilot> and <http://leepike.github.com/Copilot/> [2] <http://hackage.haskell.org/package/atom> Regards, Lee

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Re: internship opportunities in France
by Lee Pike 08 Nov '10

08 Nov '10

Hi, On a (possibly-related) note: Galois, Inc. and the National Institute of Aerospace (NIA) will likely be hosting a Visiting Scholar this summer for a joint NASA-sponsored project, located in Virginia, on the East coast of the U.S. (Since this particular opportunity is a visiting scholar position, we pay all travel/living expenses, but no salary, so one does not need a visa/work permit to work in the U.S.) We had two visiting scholars last summer, from Germany and France respectively, publishing a paper and even flying some aircraft <http://www.galois.com/blog/2010/09/22/copilot-a-dsl-for-monitoring-embedded…>. The project is a Haskell DSL project focused on monitoring embedded systems. Interested folks can contact Alwyn Goodloe (Cc'ed) at the NIA and myself, off the list. Regards, Lee > Hello folks ! > I am a Computer Science student looking for an internship of 6 months here > in France. Does anybody know of any company working with Haskell ? > Thanks in advance :D, > > Lorenzo Fundaró García

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How can I use MACID in my existing application?
by Dupont Corentin 08 Nov '10

08 Nov '10

Hello, I'm wondering how can I use Happstack's MACID in my application without breaking everything. I have a monad like that: type Comm = StateT Communication IO type GameState a = StateT Game Comm a and many functions like: foo :: GameState () foo = do lift $ putComm <some message to player's channel> modify <someAction> The state of the game is stored in Game. Comm is used as an abstraction to communicate over several channels with players. Whereas MACID asks to use: type *Update* state = Ev<http://happstack.com/docs/0.5.0/happstack-state/Happstack-State.html#t%3AEv>( StateT<http://happstack.com/docs/0.5.0/mtl/Control-Monad-State-Lazy.html#t%3AStateT>state STM <http://happstack.com/docs/0.5.0/base/GHC-Conc.html#t%3ASTM>) How can I use this without modifying everything?? I understand that MACID must record the <someAction> from above but the message should not. Thanks for help! Corentin

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"Best practices" for Text
by Ivan Lazar Miljenovic 08 Nov '10

08 Nov '10

With the recent discussions on the libraries mailing list about the API of Bryan O'Sullivan's text library, and the fact that I'm looking at using it soon for the first time, are there any recommended best practices or tips & tricks people have come up with? For starters, I'm considering writing a polyparse [1] instance for Text. However, even with the current Bytestring instances for polyparse there seems to be an emphasis on character-based parsing. Is that the correct way of doing things? For example, what would be the best way to try to parse a text value when you don't care about case? At the moment, with my String-based parser, I'm doing repeated comparisons on Char values [2,3]. [1]: http://hackage.haskell.org/package/polyparse [2]: http://hackage.haskell.org/packages/archive/graphviz/2999.10.0.1/doc/html/s… [3]: http://hackage.haskell.org/packages/archive/graphviz/2999.10.0.1/doc/html/s… -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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ANNOUNCE: seal-module
by Joachim Breitner 08 Nov '10

08 Nov '10

Hi Cafe, for those who are not following planet haskell: I uploaded a module providing a template haskell solution to the configuration problem to hackage: http://hackage.haskell.org/package/seal-module It turns the style you prefer to write in (pure code that uses configuration values as if they were global constants) into the style that is semantically correct (pure code with configuration values as an additional parameter). The module is well documented, so as soon as hackage has built the documentation you can read how it works on http://hackage.haskell.org/packages/archive/seal-module/0.1.0.1/doc/html/La… BTW: Is there a way to avoid having to indent a declarations passed to a top-level splice? Currently, one has to write: splice [d| some = declaration |] but splice [d| some = declaration |] would be nicer. Greetings, Joachim -- Joachim "nomeata" Breitner mail: mail(a)joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C JID: nomeata(a)joachim-breitner.de | http://www.joachim-breitner.de/ Debian Developer: nomeata(a)debian.org

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hmatrix's fitModel function crashes ghc(i)
by Vivian McPhail 08 Nov '10

08 Nov '10

> Message: 29 > Date: Sat, 6 Nov 2010 13:22:10 +0100 > From: Roel van Dijk <vandijk.roel(a)gmail.com> > Subject: [Haskell-cafe] hmatrix's fitModel function crashes ghc(i) > To: Haskell Caf? <haskell-cafe(a)haskell.org> > Message-ID: > <AANLkTim5eGSL_BZ%2BRUv-%3Dd-Z3DB65Sc8o%3DcKQLTcyKT4(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > Hello, > > I would like to use hmatrix to do some function fitting with the > Levenberg Marquardt algorithm. As an example I would like to fit the > very simple function "f x = a*x + b" on some data points. The problem > is that executing the 'fitModel' function crashes GHC(i) with a > segmentation fault. This makes debugging difficult. Can anyone spot > what I am doing wrong? Given all the lists of Double's it seems very > easy to make an error regarding the number of arguments with the model > function or the derivative. > > Try to evaluate the 'test' function in the small program listed below. > I would expect an output of [1, 0] (y = 1*x + 0) instead of a > segmentation fault. > > Relevant versions: > - hmatrix-0.10.0.0 > - gsl-1.14 > - ghc-6.12.3 (64 bit) > > Is that the 64 bit Linux ghc? I think the problem is with the GSL random number generation through GHCi. Try: > module Test where > > Import Numeric.Container(RandDist,randomVector) > > seed = 0 > size = 100 > > main = putStrLn $ show $ randomVector seed Gaussian size This should work when compiled with `ghc --make` and crash when invoked in `ghci`. I think the problem is with linking static data in GHCi on x86_64. Hope this helps. I seem to recall there might be a ghc trac ticket related to this but a quick search turned up nothing. Cheers, Vivian

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ANNOUNCE: arrow-list. List arrows for Haskell.
by Sebastiaan Visser 08 Nov '10

08 Nov '10

Hi all, Live from the Hackaton in Ghent, Belgium, I present the first release of the arrow-list[1,2] package. List arrows are a powerful tool when processing XML, building query languages and lots of other domains that build on functions that might return more than one value as their output. This package is inspired by the arrow combinators provided by the HXT package, but in my opinion list arrows deserve to be on Hackage on their own. Cheers, Sebastiaan [1] http://hackage.haskell.org/package/arrow-list [2] https://github.com/sebastiaanvisser/arrow-list ------------------------------------------------------------------------ (package description) List arrows for Haskell. This small Haskell library provides some type class, types and functions to work with list arrows. List arrows represent computations that may return multiple outputs. Making functions that return lists an instance of both the `Category` and `Arrow` type classes allow you to easily compose multiple computations into one with standard building blocks. This package provides: - A type class `ArrowList` for embedding functions that produce a list of outputs into _some_ list arrow. - A list of utility functions for working with list-arrows, these functions are based on the `ArrowList` type class so they are not tied one specific instance. - A concrete list arrow type that is implemented as a `Kleisli` arrow over the `ListT` list monad transformer. In short, you can both build pure list arrows and list arrows that produce tributary effects. - Not list arrow specific: A type class `ArrowKleisli` for embedding monadic computations into an arrow.

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