- Haskell-Cafe - Haskell.org

Installing REPA
by Dominic Steinitz 11 Apr '12

11 Apr '12

Hi, I'm trying to install REPA but getting the following. Do I just install base? Or is it more complicated than that? Thanks, Dominic. Tests-MacBook-Pro:PDE Test$ cabal install repa Resolving dependencies... cabal: cannot configure repa-2.2.0.1. It requires base ==4.4.* For the dependency on base ==4.4.* there are these packages: base-4.4.0.0 and base-4.4.1.0. However none of them are available. base-4.4.0.0 was excluded because of the top level dependency base -any base-4.4.1.0 was excluded because of the top level dependency base -any Tests-MacBook-Pro:PDE Test$ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library Tests-MacBook-Pro:PDE Test$ Tests-MacBook-Pro:PDE Test$ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.3

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building ghc on arch linux ARM?
by . 11 Apr '12

11 Apr '12

Hi Cafe, I hope this is the right place to ask this kind of stuff. I would like to try ghc on a panda board (armv7l) with arch linux. There is apparently no pre-built package, so I was trying the instructions to build, from here: <http://hackage.haskell.org/trac/ghc/wiki/Building/Porting>. However, I still seem to need a ghc and ghc-pkg installed: I am getting this error message: .... checking for tar... /bin/tar checking for gpatch... no checking for patch... /usr/bin/patch checking for dtrace... no checking for HsColour... no checking for xmllint... no configure: WARNING: cannot find xmllint in your PATH, you will not be able to validate your documentation checking for xsltproc... no configure: WARNING: cannot find xsltproc in your PATH, you will not be able to build the HTML documentation checking for dblatex... no configure: WARNING: cannot find dblatex in your PATH, you will not be able to build the PDF and PS documentation checking for ghc-pkg matching ... configure: error: Cannot find matching ghc-pkg --------- Does anyone know if it is possible to build ghc without ghc on this platform? I was using the tarball sources for ghc 7.4.1. Thanks, Christian

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Reconstructing a tree from a list of its paths (to leaves)
by Arnaud Bailly 10 Apr '12

10 Apr '12

Hello, I am manipulating labeled multiway trees, some kind of "lightweight" XML notation. One thing I would like to be able to do is manipulating a tree as a list of (Path, Value). Generating such a list is easy but I am a little bit surprised to find it harder to reconstruct a tree, given such a list assuming some sensible properties (list is ordered, for example). I got the intuition this has already been tackled in one way or another in a functional setting in Haskell (I code in Java but using mostly functional constructs), but don't know where to look. Thanks for your pointers and help, Regards, Arnaud

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XMPP library recommendations
by John Goerzen 10 Apr '12

10 Apr '12

Hi folks, I'm looking for suggestions for XMPP libraries. So far I have found three on Hackage. Thanks to the authors of these - I think a lot of good can come from XMPP in Haskell. However, all of them appear to be minimally maintained, if at all: * XMPP - only one upload, over 2 years ago. Does not support TLS (required by many modern servers). Does not support SASL (also required by many modern servers). After finding the options on a test server to disable the requirements for TLS and SASL, it worked. * network-protocol-XMPP - uploaded recently to fix 7.4 build issue, not much other recent activity. Refuses to connect to a test account with "Received empty challenge" (this does not appear to be an accurate error message, but rather a bug in XML parsing). A bit more low-level than I'm looking for. * haskell-xmpp - only one upload, over 1 year ago. Connects and works. I like the design. Is hard-coded to write debug messages to stdout, making it a bit of a problem for programs that use stdout (though a one-liner mod to the code would fix that). Says it's "alpha" and "work in progress". What experience do people have with these? Any recommendations? Thanks, -- John

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ANN: Selenium WebDriver client for Haskell
by Adam Curtis 10 Apr '12

10 Apr '12

The first release of the webdriver package has been uploaded to Hackage. Selenium is a test suite that allows you to automate web browsers on a variety of platforms. The webdriver package acts as a client library that speaks Selenium's WebDriver protocol, using a simple monadic interface. This alpha release has received a month of testing through my own usage, and has most of the capabilities of the official Selenium clients, with more to come. Future plans include utilizing the http-conduit and attoparsec-conduit packages for memory efficient JSON parsing, and using the reflection package to safely handle multiple versions of the WebDriver protocol through implicit configurations. For more information, see http://hackage.haskell.org/package/webdriver

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Mixing Unboxed Mutable Vectors and Parsers
by Myles C. Maxfield 10 Apr '12

10 Apr '12

CC: Maintainers of STMonadTrans, Vector, and JuicyPixels Hello, I am writing a Haskell Attoparsec parser which will modify 2-d arrays of small values (Word8, Int8, etc.). My first idea was to simply parse all the deltas, and later apply them to the input list. However, I can't do that because the value of the deltas depend on the value they're modifying. My first pass at this program used a function of the form: p :: [[Word8]] -> Parser [[Word8]] This approach works, however, the program uses far too much memory. Some quick testing shows that lists of Word8s are ~52.6x larger than unboxed vectors of Word8s, and boxed vectors of Word8s are ~7.5x larger than unboxed vectors of Word8s. A better approach would be to use Data.Vector.Unboxed.Mutable and do the mutations inline with the parser. Because mutable vectors require a monad in PrimMonad to do the mutations inside of, I'd have to use a monad transformer to combine Parser and something in PrimMonad. Attoparsec doesn't support being used as a monad transformer, so I can't say something like p :: (PrimMonad m, UM.Unbox a) => M.MVector (PrimState m) (UM.MVector (PrimState m) a) -> ParserT m () I can't use Parsec (instead of Attoparsec) because I require streaming semantics -- eventually I'm going to hook this up to Data.Conduit and parse directly from the net. There is STT (in the package STMonadTrans), however, so I could potentially make the function result in STT Parser (). However, STT doesn't work with Data.Vector.Mutable or Data.Vector.Unboxed.Mutable, because STT isn't a member of the PrimMonad class (as far as I can tell). STT itself doesn't define unboxed mutable vectors (only boxed mutable vectors), but I feel that giving up unboxing isn't really an option because of the memory footprint. As a general observation, it seems silly to have two different mutable vector implementations, one for STT and the other for PrimMonad. So here are my questions: 1. Is it possible to implement PrimMonad with STT? I looked around for a little while, but couldn't find anything that did this. 2. Otherwise, is it reasonable to try to implement unboxed mutable vectors in STT? I feel this is probably going down the wrong path. 3. Are there any parsers that support streaming semantics and being used as a monad transformer? This would require rewriting my whole program to use this new parser, but if that's what I have to do, then so be it. Thanks, Myles C. Maxfield

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Call for Participation: Tests and Proofs (TAP 2012) in Prague
by Achim D. Brucker 10 Apr '12

10 Apr '12

Apologies for duplicates. ======================================================================== CALL FOR PARTICIPATION TESTS and PROOFS 2012 (TOOLS EUROPE 2012) 6th International Conference on Tests & Proofs May 31 - June 1, 2012, Prague, Czech Republic http://lifc.univ-fcomte.fr/tap2012/ Co-located with: ICMT 2012, SC 2012, MSEPT 2012 as part of TOOLS 2012: http://toolseurope2012.fit.cvut.cz/ ======================================================================== The TAP conference is devoted to the convergence of proofs and tests. It combines ideas from both sides for the advancement of software quality. Keynote Speakers ================ * Andreas Kuehlmann <http://www.eecs.berkeley.edu/%7Ekuehl/>, Coverity The Technology and Psychology of Testing Your Code as You Develop It (abstract <http://lifc.univ-fcomte.fr/tap2012/abstract_talk_Kuehlmann.pdf>) * Corina Pasareanu <http://ti.arc.nasa.gov/profile/pcorina/>, NASA Ames Research Center Combining Model Checking and Symbolic Execution for Software Testing (abstract <http://lifc.univ-fcomte.fr/tap2012/abstract_talk_Pasareanu.pdf>) * Mehdi Jazayeri, University of Lugano. Software Composition: Why, what, and how Registration: ============= Early registration, at a reduced price, will be open until 25 April 2012. http://toolseurope2012.fit.cvut.cz/index.php/registration.html Organization: ============= Conference Chair Bertrand Meyer, ETH Zurich, Eiffel Software, and ITMO Program Chairs Achim D. Brucker, SAP Research, Germany Jacques Julliand, University of Franche-Comté Local Organization Pavel Tvrdik, CTU Prague Michal Valenta, CTU Prague Jindra Vojikova, CTU Prague Jan Chrastina, CTU Prague Program: ======== Thursday 31th May, 09:00-10:30: Invited Talk * Andreas Kuehlmann, Coverity: The Technology and Psychology of Testing Your Code as You Develop It Thursday, 11:00-13:00: Paper session Model-Based Testing * Malte Lochau, Ina Schaefer, Jochen Kamischke and Sascha Lity. Incremental Model-based Testing of Delta-oriented Software Product Lines * Hernan Ponce De Leon, Stefan Haar and Delphine Longuet. Conformance Relations for Labeled Event Structures * Joseph Kiniry, Daniel M. Zimmerman and Ralph Hyland. Testing Library Specifications by Verifying Conformance Tests * Chedor Sebastien, Thierry J?ron and Morvan Christophe. Test generation from recursive tiles systems Thursday, 14:30-15:30: Paper session Scenario and UML-Based Testing * Nadia Creignou, Uwe Egly and Martina Seidl. A Framework for the Specification of Random SAT and QSAT Formulas * Jens Brüning, Martin Gogolla, Lars Hamann and Mirco Kuhlmann. Evaluating and Debugging OCL Expressions in UML Models * Uwe Egly, Sebastian Gabmeyer, Martina Seidl, Hans Tompits, .... Towards Scenario-Based Testing of UML Diagrams Thursday, 16:00-17:00: Tutorial * Nikolay Kosmatov, Nicky Williams. Automated Structural Testing with PathCrawler Friday 1st June, 09:00-10:30: Invited Talk of SC * Mehdi Jazayeri, University of Lugano. Software Composition: Why, what, and how Friday 11:00-13:00: Invited Talk of TAP * Corina Pasareanu. NASA. Combining Model Checking and Symbolic Execution for Software Testing Friday, 14:30-15:30: Paper session Test and Model-checking * Martin Sulzmann and Axel Zechner Constructive Finite Trace Analysis with Linear Temporal Logic * Alessandro Armando, Roberto Carbone, Giancarlo Pellegrino, Alessio Merlo and Davide Balzarotti. From Model-checking to Automated Testing of Security Protocols: Bridging the Gap Friday, 16:00-17:30: Paper session Test of Complex Data Structures * Valerio Senni and Fabio Fioravanti. Generation of test data structures using Constraint Logic Programming * Valeria Bengolea, Nazareno Aguirre, Darko Marinov and Marcelo Frias. Coverage Criteria on RepOK to Reduce Bounded Exhaustive Test Suites * Matthieu Carlier, Catherine Dubois and Arnaud Gotlieb. A first step in the design of a formally verified constraint-based testing tool: FocalTest -- Dr. Achim D. Brucker, SAP Research, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, http://www.brucker.ch

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ANN: plugins-1.5.2.1
by Jeremy Shaw 09 Apr '12

09 Apr '12

Hello! I am pleased to announce the release of plugins-1.5.2.1: http://hackage.haskell.org/package/plugins The plugins library provides facilities to compile and dynamically load/link Haskell code into a running Haskell application. (The related, plugins-auto package adds support for file watching via inontify and automatic recompilation and reloading, http://hackage.haskell.org/package/plugins) There are three important changes in this release: 1. Support for GHC 7.0, 7.2. and 7.4. We have not *knowingly* dropped support for GHC 6.12. So, if you still use an older compiler and we broke it.. we might be willing to fix it still :) 2. New maintainer: Don Stewart has graciously allowed me to take over the project. I do not have any immediate plans for big changes. But I do plan to: keep it compiling, apply patches in a timely manner, and deal with other minor bug fixes. I would certainly love to see some major improvements. I believe plugins predates the GHC API and, accordingly, does not use it as well as it could. If someone wanted to give plugins some major love, that would be awesome. While plugins has not much recent development, there are still a lot of people that are using it, or would like to. 3. the source has moved to patch-tag and darcs 2, http://patch-tag.com/r/stepcut/plugins patch-tag only supports darcs 2 format repositories, so this forced me to run darcs convert to switch from darcs 1 to darcs 2 format. In the end that is a good thing. The only downside is that I can not directly apply any darcs 1 patches to the repo now. But I doubt there are many floating around anyway. And I can still apply them the hard way. - jeremy

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Guide for converting existing code to Conduit 0.4?
by Erik de Castro Lopo 09 Apr '12

09 Apr '12

Hi all, Is there some sort of a guide for converting existing code Conduit 0.4? What happened to Control.Monad.Trans.Resource.with? What happens to stuff that used to to have a type "C.Source m a" which now seems to need type "C.Pipe Void a (ResourceT m) a"? Cheers, Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/

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Category Theory Questions
by Sergiu Ivanov 09 Apr '12

09 Apr '12

Hello, I have a question not that directly related to Haskell, but I still think this is a good place to ask it. I am currently studying category theory by the book Joy of Cats. Are there any people whom I could ask some questions related to category theory from time to time? Or could I just post my questions here directly? The reason I'm asking is that I seen very nice discussions related to category theory on this list. I hope to be able to deal with most of the stuff myself, but having someone to discuss the matters with is always nice :-) Sergiu [0] katmat.math.uni-bremen.de/acc/acc.pdf

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