December 2011 - Haskell-Cafe

Hexpat: Lazy I/O problem with huge input files
by Aleksandar Dimitrov 11 Dec '11

11 Dec '11

Hello Haskell Cafe, I really hope this is the right list for this sort of question. I've bugged the folks in #haskell, they say go here, so I'm turning to you. I want to use Hexpat to read in some humongous XML files (linguistic corpora,) since it's the only Haskell XML library (I could find) that takes ByteStrings as input. I stumbled on a problem when using one of the examples from the docs of Text.XML.Expat.Tree. The "cookbook recipe" there suggests *first* processing the data, and only then looking into the parser error to see if there has been an error. I understand this should prevent the parse tree from being fully evaluated before use. Unfortunately, that is not what happens on my system (ghc 6.12.1, if that's of importance.) This is the code from the docs, that I modified to read files: > import Text.XML.Expat.Tree > import System.Environment (getArgs) > import Control.Monad (liftM) > import qualified Data.ByteString.Lazy as C >· > -- This is the recommended way to handle errors in lazy parses > main = do > f <- liftM head getArgs >>= C.readFile > let (tree, mError) = parse defaultParseOptions f > print (tree :: UNode String) >· > -- Note: We check the error _after_ we have finished our processing > -- on the tree. > case mError of > Just err -> putStrLn $ "It failed : "++show err > Nothing -> putStrLn "Success!" Given a 42M test file, an invocation like this: % ghc --make -O2 Hexpat.hs % ./Hexpat input.xml > dump.xml will gobble up some 2Gigs of RAM (at least. I usually kill it before it starts thrashing the swap space, since that almost crashes my entire machine.) If I remove the last 3 lines: > import Text.XML.Expat.Tree > import System.Environment (getArgs) > import Control.Monad (liftM) > import qualified Data.ByteString.Lazy as C > > main = do > f <- liftM head getArgs >>= C.readFile > let (tree, mError) = parse defaultParseOptions f > print (tree :: UNode String) the same invocation and input file barely uses a megabyte or two of RAM and finishes really quickly. Why is that? Is this a mistake in the Hexpat docs, or am I doing something wrong? Lazy IO has always been a little bit of a mystery to me, and just when I thought I had it... Thanks for any help on the matter! Aleks

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Beginning Data.Lens tutorial
by Henry Laxen 10 Dec '11

10 Dec '11

Dear Group, If you haven't used lenses before, (as I hadn't until recently) you may find this helpful: http://www.nadineloveshenry.com/haskell/lensExamples.html Best wishes, Henry Laxen

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Alternative STM implementation
by Daniel Waterworth 10 Dec '11

10 Dec '11

Hi, This morning I have written an STM implementation as a learning exercise. I thought I'd share it here to get some critique and because it might be useful to others (consider it as being in the public domain). I haven't tested it thoroughly, so there may be edge cases that haven't been thought through. It should be a drop-in replacement (so long as you only use TVars), if anyone has any STM benchmarks already made, I'd love to see how it compares. Here it is: https://gist.github.com/1454995 Thanks, Daniel

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Haskell functions caller-callee details
by Shakthi Kannan 10 Dec '11

10 Dec '11

Hi, Given a Haskell package is there a way I can get each functions' caller-callee details? Are there any existing tools/libraries that can help me get this data from the source? Appreciate any inputs in this regard. Thanks! SK -- Shakthi Kannan http://www.shakthimaan.com

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Cabal issue
by Kevin Jardine 10 Dec '11

10 Dec '11

I understand that this may have been addressed before on this list in some form, so I'll be brief: Had problem with deprecated package, was told my only option was to wipe my Haskell install and start over. Is this true and if so, doesn't this mean that Cabal (or the package management system that it is a part of) is broken? Details here: https://plus.google.com/u/0/111705054912446689620/posts/V1186HGWEap Kevin

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ANNOUNCE: Workflow-0.5.8.0
by Alberto G. Corona 10 Dec '11

10 Dec '11

This is A new version of the package workflow. I probably will change the name of this package since it is too generic. A workflow can be seen as a persistent thread that executes a monadic computation. Therefore, it can be used in very time consuming computations such are CPU intensive calculations with intermediate results or with procedures that are most of the time waiting for the response of a process or an user, that are prone to comunication failures, timeouts or shutdowns. Workflow has a operation, called "step" that lift the monadic computation to the Workflow monad. This bring services of transparent state loogging, so that the computation can be restarted at the point of stop/failure. Additionally , the package has persistent queues, persistent data collections, and persistent timeouts (whit which the workflow can wait for days, months or even years, more than the average time between failures). This is important for programming office workflow or in election processes where the user has a limited time to decide/vote. This version has many improvements: it admits Data.Binary serialization for logging (besides RefSerialize of previous versions). . It also has an EDSL of high level monadic combinators that represent workflow patterns. For example, split, merge, synchronization, votation etc. There are examples in the online documentation and some demos in the package. My motivation for developping Workflow is to use it in a project for electronic democracy in the Web. If anyone is interested in the package Workflow and/or electronic democracy, I will be happy to talk with him. Hope to be useful Alberto.

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ANNOUNCE: HaTeX 3.1.0 (and HaTeX-meta 1.1.0)
by Daniel Díaz Casanueva 10 Dec '11

10 Dec '11

Hello Cafe! Today I released to Hackage a new version of the HaTeX package ( http://hackage.haskell.org/package/HaTeX-3.1.0 ). If you don't know HaTeX, it is a combinator library of the LaTeX syntax. Visit the homepage for more information: http://dhelta.net/hprojects/HaTeX Highlights: + Added warnings (See Text.LaTeX.Base.Warnings). Still very experimental. + Added an "Examples" directory, with a simple example inside to get started. + Num instance for LaTeX and LaTeXT. + New package implemented "AMSThm" (See Text.LaTeX.Packages.AMSThm). See the ReleaseNotes in the source tarball for more details in release changes. With it, I released an update of HaTeX-meta (version 1.1.0), which produces part of the HaTeX code. An important change here is the addition of the HATEX pragma (explained in http://deltadiaz.blogspot.com/2011/11/hatex-pragma.html ). If you need something more, feel free to contact me or send me a patch.

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Does anyone maintain trac.haskell.org?
by Justin Bailey 09 Dec '11

09 Dec '11

The community Trac hosting server isn't sending email, which Trac requires. I've submitted several tickets to support(a)community.haskell.org but gotten no response. Does anyone maintain that server anymore? Justin

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CfP: Only one week left for submitting abstracts to TAP 2012 (International Conference on Test and Proofs
by Achim D. Brucker 09 Dec '11

09 Dec '11

(Apologies for duplicates) ************************************************* **** Less than one week until the deadline *** **** for submitting abstract to TAP 2012 *** ************************************************* CALL FOR PAPERS Full and short Research Paper, Industrial Expierence Papers, Tool Papers Abstract submission: Dec 14, 2011, Paper submission Dec 21, 2012 6th INTERNATIONAL CONFERENCE ON TEST AND PROOFS (TAP 2012) http://lifc.univ-fcomte.fr/tap2012/ May 31 - June 1, 2012, Prague, Czech Republic Part of the TOOLS Federated Conferences 2012 http://tools2012.fit.cvut.cz/ The TAP conference is devoted to the convergence of proofs and tests, to the application of techniques from both sides and their combination for the advancement of software quality. Test and Proof seem to be contradictory techniques: if you have proved your program to be correct, it is fruitless to comb it for bugs; and if you are testing it, that is surely a sign that you have given up on any hope to prove its correctness. Accordingly, proofs and tests have, since the onset of software engineering research, been pursued by distinct communities. However, the development of both approaches lead to the discovery of common issues and to the realization that each may need the other. The emergence of model checking has been one of the first signs that contradiction may yield to complementarity. Further evidence give test data generation techniques from models or programs which boil down to constraint resolution techniques for relatively large formula; the advent of powerful SMT solvers have therefore powered new testing techniques. Finally, since formal, proof-based verification is costly, testing invariants and background theories can be helpful to detect errors early and to improve cost effectivity. Summing up, in the past few years an increasing number of research efforts have encountered the need for combining proofs and tests, dropping earlier dogmatic views of incompatibility and taking instead the best of what each of these software engineering domains has to offer. The TAP conference aims to bring together researchers and practitioners working in the converging fields of testing and proving, and will offer a generous allocation of papers, panels and informal discussions. Topics of interest cover theory definitions, tool constructions and experimentations and include (other topics related to TAP are welcome): - Transfer of concepts from testing to proving (e.g., coverage criteria) and from proving to testing - Program proving with the aid of testing techniques - New problematics in automated reasoning emerging from specificities of test generation - Verification and testing techniques combining proofs and tests - Generation of test data, oracles, or preambles by deductive techniques such as: theorem proving, model checking, symbolic execution, constraint logic programming - Model-based testing and verification - Generation of specifications by deduction - Automatic bug finding - Debugging of programs combining static and dynamic analysis - Formal frameworks - Tool descriptions and experience reports - Case studies combining tests and proofs - Applying combination of test and proof techniques to new application domains such as validating security procotols or vulnerability detection of programs Important Dates: ================ Abstract submission: December 14, 2011 Paper submission: December 21, 2011 Notification: March 2, 2012 Camera ready version: March 19, 2012 TAP conference: May 31 - June 1, 2012 (to be confirmed) TOOLS conferences (TOOLS, ICMT, SC, TAP): May 29 - June 01, 2012 Conference Chairs: Bertrand Meyer Program Chairs: Achim D. Brucker and Jacques Julliand Program Committee (to be extended): =================================== Nazareno Aguirre, Bernhard K. Aichernig, Paul Ammann, Dirk Beyer, Nikolaj Bjorner, Robert Clarisó, Marco Comini, Catherine Dubois, Gordon Fraser, Angelo Gargantini, Alain Giorgetti, Patrice Godefroid, Martin Gogolla, Arnaud Gotlieb, Reiner Hähnle, Bart Jacobs, Thierry Jéron, Gregory Kapfhammer, Nikolai Kosmatov, Victor Kuliamin, Karl Meinke, Jeff Offutt, Holger Schlingloff, T.H. Tse, Margus Veanes, Luca Viganò, Burkhart Wolff, Fatiha Zaidi Submission: =========== Please submit your papers via http://lifc.univ-fcomte.fr/tap2012/. TAP 2012 will accept two types of papers: - Research papers: full papers with at most 16 pages in LNCS format (pdf), which have to be original, unpublished and not submitted elsewhere. - Short contributions: work in progress, (industrial) experience reports or tool demonstrations, position statements; an extended abstract with at most 6 pages in LNCS format (pdf) is expected. Accepted papers will be published in the Springer LNCS series and will be available at the conference. The contents of previous TAP proceedings is available at: http://www.informatik.uni-trier.de/~ley/db/conf/tap/ -- Dr. Achim D. Brucker, SAP Research, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, Fax: +49-6227 78-50502, http://www.brucker.ch

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[ANNOUNCE] cereal-0.3.5.0
by Trevor Elliott 09 Dec '11

09 Dec '11

Hi Everyone, I'm pleased to announce the release of cereal version 0.3.5.0! New to this release is support for default, generic implementations of the get and put methods of the Serialize class, when support is available. This functionality comes to you courtesy of Bas van Dijk. Happy Hacking! --trevor

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