- Haskell-Cafe - Haskell.org

containers license issue
by Dmitry Kulagin 19 Dec '12

19 Dec '12

Hi Cafe, I am faced with unpleasant problem. The lawyer of my company checked sources of containers package and found out that it refers to some GPL-library. Here is quote: "The algorithm is derived from Jorg Arndt's FXT library" in file Data/IntMap/Base.hs The problem is that FXT library is GPL and thus containers package can not be considered as BSD3. And it means that it can not be used in my case (closed source software). Is this logic actually correct and containers should be considered as GPL? The package is widely used by other packages and the only way I see right now is to fix sources to reimplement this functionality, which is not good option. Thank you!

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Re: [Haskell-cafe] Tail recursive
by J.W. Krol 19 Dec '12

19 Dec '12

From: jkrzzz(a)live.com To: haskell-cafe(a)haskell.org Subject: Tail recursive Date: Wed, 19 Dec 2012 17:07:14 +0100 Hello, I need a non tail recursive version of scanl, to produce a large enough list of >100K vectors (vectors defined as a list) I have following code: scanl'::(a -> a -> a) -> a -> [a] -> [a]scanl' f q ls = scanl'' ls (q:[]) where scanl'' (x:xs) ys = let h = head ys x' = f x h ys' = x':ys in h `seq` x' `seq` ys' `seq` scanl'' xs ys' scanl'' [] ys = ys If I call this function as below I still got stack-overflow error: head (scanl' (zipWith (+)) ([0,0]) (take 100000 (repeat [0,1]))) What do I wrong. I am not an experienced Haskell programmer, but find the behavior quite unexplainable. Thank for your answer. RegardsJacq

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A weird bug of regex-pcre
by Magicloud Magiclouds 19 Dec '12

19 Dec '12

Attachment is the test text file. And I tested my regexp as this: Prelude> :m + Text.Regex.PCRE Prelude Text.Regex.PCRE> z <- readFile "test.html" Prelude Text.Regex.PCRE> let (b, m ,a, ss) = z =~ "<a href=\"(.*?)\">.*?<img class=\"article-image\"" :: (String, String, String, [String]) Prelude Text.Regex.PCRE> b ... n of the Triumvirate</td>\r\n <td class=\"small\">David Rapoza</td>\r\n <td class=\"small\">\r\n <i>Return to Ravnica</i>\r\n </td>\r\n <td class=\"small\">10/31/2012</td>\r\n </tr><tr>\r\n <td class=\"small\"><" Prelude Text.Regex.PCRE> m "a href=\"/magic/magazine/article.aspx?x=mtg/daily/activity/1088\"><img class=\"article-image\" " >From the value of b and m, it was weird that the matching was moved forward by 1 char ( the ss (sub matching) was even worse, 2 chars ). Rematch to a and so on gave correct results. It was only the first matching that was broken. Tested with regex-posix (with modified regexp), everything is OK. $ ghc-pkg describe regex-pcre name: regex-pcre version: 0.94.4 id: regex-pcre-0.94.4-d45e00c9e113c7c9352d0785497e1dca license: BSD3 copyright: Copyright (c) 2006, Christopher Kuklewicz maintainer: TextRegexLazy(a)personal.mightyreason.com stability: Seems to work, passes a few tests homepage: http://hackage.haskell.org/package/regex-pcre package-url: http://code.haskell.org/regex-pcre/ synopsis: Replaces/Enhances Text.Regex description: The PCRE backend to accompany regex-base, see www.pcre.org category: Text author: Christopher Kuklewicz exposed: True exposed-modules: Text.Regex.PCRE Text.Regex.PCRE.Wrap Text.Regex.PCRE.String Text.Regex.PCRE.Sequence Text.Regex.PCRE.ByteString Text.Regex.PCRE.ByteString.Lazy hidden-modules: trusted: False import-dirs: /home/magicloud/.cabal/lib/regex-pcre-0.94.4/ghc-7.6.1 library-dirs: /home/magicloud/.cabal/lib/regex-pcre-0.94.4/ghc-7.6.1 hs-libraries: HSregex-pcre-0.94.4 extra-libraries: pcre extra-ghci-libraries: include-dirs: includes: depends: array-0.4.0.1-cbe8814e07792e8f0d66cac77a2c0b6b base-4.6.0.0-9108e251636b0c8499261c52a7809ea1 bytestring-0.10.0.1-11d4f52c4f4ed9833f768577b77050c5 containers-0.5.2.1-b183418bc7f43ce98b6916ef296c2669 regex-base-0.93.2-1ee07f806ad6b0c911226883d15b64f2 hugs-options: cc-options: ld-options: framework-dirs: frameworks: haddock-interfaces: /home/magicloud/.cabal/share/doc/regex-pcre-0.94.4/html/regex-pcre.haddock haddock-html: /home/magicloud/.cabal/share/doc/regex-pcre-0.94.4/html pkgroot: "/home/magicloud/.ghc/x86_64-linux-7.6.1" -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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efficient data structure: column with repeating values
by Christopher Howard 19 Dec '12

19 Dec '12

Is there some good data type out there that basically provides a simple table, but with optimization for repeating values on one column? Something like: Data Table a b ...where it assumes that 'a' values will usually be unique, while 'b' values will usually be repeated from a small set? (But not needing to be fixed beforehand.) Like in... client | patron --------------- Bob | Tom Sarah | Tom Dick | Tom George | Harry Moe | Harry -- frigidcode.com

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Incremental regular expressions - article and library
by Eugene Kirpichov 19 Dec '12

19 Dec '12

Hi Haskellers, I just published an article that can be interesting to lovers of functional programming, even though it's not directly relevant to Haskell per se. http://jkff.info/articles/ire/ It's based on Dan Piponi's blogpost "Fast incremental regular expression matching with monoids" http://blog.sigfpe.com/2009/01/fast-incremental-regular-expression.html but expands Dan's ideas to include *locating* matches, matching multiple regular expressions at once, using a more compact datastructure than fingertrees, etc. And - sorry - the implementation is in Java, for reasons explained in the article :) -- Eugene Kirpichov http://www.linkedin.com/in/eugenekirpichov

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HTF & Quickcheck
by graham＠fatlazycat.com 18 Dec '12

18 Dec '12

Getting test failures, I believe, due to using conditional properties within quickckeck etc [TEST] RecFunSpec:map (test/RecFunSpec.hs:48) Gave up! Passed only 20 tests. *** Failed! (2ms) Is there a way for HTF/Quickcheck to specify these are not failed i.e. only fail if there is an actual error ? Thanks

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Race Condition in threads
by mukesh tiwari 18 Dec '12

18 Dec '12

Hello All I have two questions. 1. I wrote this code to create 10 simultaneous threads. Could some one please tell me if this is correct or not ? incr_count :: MVar () -> MVar Int -> IO () incr_count m n = ( forM_ [ 1..10000 ] $ \_ -> modifyMVar_ n ( return . ( + 10 ) ) ) >> putMVar m () main :: IO() main = do count <- newMVar 0 list <- forM [1..10] $ \_ -> newEmptyMVar forM_ list $ \var -> forkIO . incr_count var $ count forM_ list $ \var -> takeMVar var val <- takeMVar count print val 2. I am trying to create race condition which makes the variable in inconsistent state. Could some one please tell me how to achieve this ? I look at IORef but it does not have function like modifyMVar_. Mukesh Tiwari

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TAP 2013: 2nd Call for Papers
by Achim D. Brucker 18 Dec '12

18 Dec '12

(Apologies if you receive this announcement multiple times.) **************************************************** *** *** *** TAP 2013 *** *** *** *** Abstract submission: January 25, 2013 *** *** Paper submission: February 1, 2013 *** **************************************************** *** TAP 2013 solicits both full papers and *** *** (industrial) experience/tool papers *** *** in combining proofs and (security) testing *** **************************************************** CALL FOR PAPERS 7th INTERNATIONAL CONFERENCE ON TESTS AND PROOFS (TAP 2013) http://www.spacios.eu/TAP2013 Budapest, Hungary, June 18-19, 2013 The TAP conference is devoted to the synergy of proofs and tests, to the application of techniques from both sides and their combination for the advancement of software quality. Testing and proving seem to be contradictory techniques: once you have proved your program to be correct then additional testing seems pointless; on the other hand, when such a proof in not feasible, then testing the program seems to be the only option. This view has dominated the research community since the dawn of computer science, and has resulted in distinct communities pursuing the seemingly orthogonal research areas. However, the development of both approaches has lead to the discovery of common issues and to the realization of potential synergy. Perhaps, use of model checking in testing was one of the first signs that a counterexample to a proof may be interpreted as a test case. Recent breakthroughs in deductive techniques such as satisfiability modulo theories, abstract interpretation, and interactive theorem proving, have paved the way for new and practically effective methods of powering testing techniques. Moreover, since formal, proof-based verification is costly, testing invariants and background theories can be helpful to detect errors early and to improve cost effectiveness. 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): - Bridging the gap between concrete and symbolic techniques, e.g. using proof search in satisfiability modulo theories solvers to enhance various testing techniques - 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 - Domain specific applications of testing and proving to new application domains such as validating security protocols, vulnerability detection of programs, security Important Dates: ================ Abstract submission: January 25, 2013 Paper submission: February 1, 2013 Notification: March 3, 2013 Camera ready version: April 5, 2013 TAP conference: June 17-21, 2013 Program Chairs: =============== Margus Veanes (Microsoft Research, USA) Luca Vigano` (University of Verona, Italy) Program Committee: ================== Paul Ammann Dirk Beyer Achim D. Brucker Robert Clarisò Marco Comini Catherine Dubois Gordon Fraser Angelo Gargantini Christoph Gladisch Martin Gogolla Arnaud Gotlieb Wolfgang Grieskamp Reiner Hähnle Bart Jacobs Thiérry Jeron Jacques Julliand Gregory Kapfhammer Nikolai Kosmatov Victor Kuliamin Michael Leuschel Karl Meinke Alexandre Petrenko Holger Schlingloff T.H. Tse Margus Veanes (co-chair) Luca Viganò (co-chair) Burkhart Wolff Fatiha Zaidi Submission: =========== Please submit your papers via easychair https://www.easychair.org/conferences/?conf=tap2013 TAP 2013 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. Subject to final approval by Springer, 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 AG, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, http://www.brucker.ch/

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haskell-like scripting language
by Christopher Howard 17 Dec '12

17 Dec '12

I gave Shelly a try. Pretty cool - using it for some of the scripts on my system. Has me wondering though: is anyone working on creating a actual Haskell-like scripting language and engine? Shelly is cool, as I said, but I imagine it would be more valuable to have another language that is actually separate from Haskell, with an interpreter that is more lightweight and changes much less frequently (than GHC). Something that could be nearly as portable as Bash or Perl. -- frigidcode.com

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Navigating 'Strategic' programming babel
by Ravi Sahni 17 Dec '12

17 Dec '12

Clearly Haskell has great possibilities in the field of language-processing. And the nuisances associated with little actual computation buried under much data-structure navigation are well addressed by 'strategic-programming' systems. But now comes the rub -- there seem to be a lot of very similar systems. Any guidance on which/what/how to choose? My own current sketchy-patchy knowledge is as below. I would appreciate links/pointers to more substansive literature. First there was Meertens and his folks working on generic haskell Did that later become template haskell? That branched out into strafunski, stratego/xt. SYB is ___ not sure here: some literature suggests that its identical to strafunski. Some suggests that it is strafunski done more within the haskell language rather than in libraries. Then there's uniplate. How does it compare to SYB? Or is that a confused comparison?

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