September 2011 - Haskell-Cafe

ANN: cabal-ghci 0.1
by Etienne Laurin 11 Sep '11

11 Sep '11

Hello fellow hackers. Here is a helpful package I wrote to ease the development of projects using cabal. It includes a :cabalset ghci command to set ghci options for your project, and a cabal-ghci executable to launch ghci with those options. Do you get errors when loading your project into ghci? Prelude> a ← return 1 <interactive>:1:3: Not in scope: `←' Prelude> :load Main Could not find module `Main': it is not a module in the current program, or in any known package. cabalset fixes these problems for you. Prelude> :cabalset :set "-i/home/atnnn/up1/src/dist/build/autogen" :set "-i/home/atnnn/up1/src/web" :set "-XUnicodeSyntax" :set "-Wall" Prelude> a ← return 1 <interactive>:1:12: Warning: Defaulting the following constraint(s) to type `Integer' (Num t0) arising from the literal `1' Prelude> :load Main Ok, modules loaded: Main, Application, Handlers. This works from any sub-directory of your project and accepts the following arguments: -fflag enable flag -f-flag disable flag exec load options for the exec executable To install: $ cabal update $ cabal install cabal-ghci $ cat >> ~/.ghci :m + Distribution.Dev.Interactive :def cabalset cabalSet :cabalset :m - Distribution.Dev.Interactive ^D Etienne Laurin

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hledger subcommand detection, RFC
by Simon Michael 11 Sep '11

11 Sep '11

When I split up the hledger package, I always intended to make the hledger program act as a single front end for hledger-* executables. I finally got around to trying that, just pushed to darcs [1]. So hledger now searches your PATH at startup and offer any hledger-* executables as subcommands. To make this fully modular, so that options can be reused and third-party add-ons don't need to be baked in to hledger in any way, there has also been a rather extensive options overhaul, using cmdargs. Below is an example [2] of the new help output with all hledger-* packages plus a local hledger-report.hs script installed. I'm not sure if this is fully safe, cross-platform, robust, quick enough to be unnoticeable, etc. I have about 20 dirs and 4k files in my PATH. I haven't noticed a slowdown on macbook or vps, but have not measured. More testing of this on diverse platforms and machines, or code review, would be very welcome. -Simon [1] http://joyful.com/darcsden/simon/hledger/browse/hledger/Hledger/Cli/Options… [2] $ hledger hledger [COMMAND] ... [OPTIONS] run the specified hledger command. hledger COMMAND --help for more detail. In general, COMMAND should precede OPTIONS. Misc commands: add prompt for new transactions and append them to the journal convert show the specified CSV file as hledger journal entries test run self-tests, or just the ones matching REGEXPS Report commands: accounts (or balance) show matched accounts and their balances entries (or print) show matched journal entries postings (or register) show matched postings and running total activity show a barchart of transactions per interval stats show quick statistics for a journal (or part of it) Add-on commands found: chart [-- OPTIONS] run the hledger-chart program interest [-- OPTIONS] run the hledger-interest program report [-- OPTIONS] run the hledger-report program vty [-- OPTIONS] run the hledger-vty program web [-- OPTIONS] run the hledger-web program -? --help Display help message --debug Show extra debug output -V --version Print version information

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Improvements to Vim Haskell Syntax file - Is anyone the maintainer?
by David Terei 10 Sep '11

10 Sep '11

Hi All, I have made some improvements to the syntax highlighting file for Haskell included with Vim. I'd like to push them upstream. The haskell.vim syntax file included with Vim lists this mailing list as the maintainer. I take that to mean no one. Is this right or does someone actually have responsibility for the Vim Haskell syntax file? here are some screenshots of the changes I've made: http://www.scs.stanford.edu/~davidt/vim-syntax.html Cheers, David

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compiler "pragma"'s
by Vasili I. Galchin 10 Sep '11

10 Sep '11

Hello, Is there a list of compiler pragmas? Specifically I am looking at how to specify more than one type variable in a class definition. Also I have forgotten the "meta syntax" for specifying a pragma ... some kind of Haskell comment? Thanks, Vasili

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matrix manipulations and calculations
by Thomas Friedrich 09 Sep '11

09 Sep '11

Hi everyone, I need to do a lot of matrix manipulation and it needs to be fast. There seems to be a whole bunch of packages dealing with matrix calculations on HackageDB. I am wondering, what is the current state-of-the-art? I started of using hmatrix [1] now. However, I eventually would like to use some functions from the statisics-package [2]. They both use different types for their vector representations. In hmatrix a vector is of type Data.Packed.Vector. In the statistics package, vectors are based on [3]. I found this: http://www.haskell.org/haskellwiki/Linear_algebra but the last post is from 2005. That is 6 years ago. What is the state now? What would you recommend me to use? I don't want to code and then realise in a few month, I made the wrong decision. So, help is greatly appreciated. Thanks, Thomas -- [1] http://hackage.haskell.org/package/hmatrix-0.12.0.0 [2] http://hackage.haskell.org/package/statistics-0.9.0.0 [3] http://hackage.haskell.org/package/vector-0.9

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First CfP: International Conference on Test and Proofs (TAP 2012), Next Deadline: 2011-12-14
by Achim D. Brucker 09 Sep '11

09 Sep '11

(Apologies for duplicates) 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, Patrice Godefroid, Martin Gogolla, Arnaud Gotlieb, Reiner Hähnle, Bart Jacobs, Thierry Jéron, Gregory Kapfhammer, Nikolai Kosmatov, Victor Kuliamin, Karl Meinke, 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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Leipzig (Germany) Haskell Workshop 7 October - Program and Registration
by Johannes Waldmann 09 Sep '11

09 Sep '11

Dear all, the 6th Haskell in Leipzig workshop, on October 7, will present an absolutely thrilling mixture of tutorials and talks, with special emphasis on parallel programming. for details and registration, http://portal.imn.htwk-leipzig.de/events/hal6-haskell-workshop See you - Johannes Waldmann.

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Converting wiki pages into pdf
by mukesh tiwari 09 Sep '11

09 Sep '11

Hello all I am trying to write a Haskell program which download html pages from wikipedia including images and convert them into pdf . I wrote a small script import Network.HTTP import Data.Maybe import Data.List main = do x <- getLine htmlpage <- getResponseBody =<< simpleHTTP ( getRequest x ) -- open url --print.words $ htmlpage let ind_1 = fromJust . ( \n -> findIndex ( n `isPrefixOf`) . tails $ htmlpage ) $ "" ind_2 = fromJust . ( \n -> findIndex ( n `isPrefixOf`) . tails $ htmlpage ) $ "" tmphtml = drop ind_1 $ take ind_2 htmlpage writeFile "down.html" tmphtml and its working fine except some symbols are not rendering as it should be. Could some one please suggest me how to accomplish this task. Thank you Mukesh Tiwari

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mapM is supralinear?
by Travis Erdman 09 Sep '11

09 Sep '11

The performance of mapM appears to be supralinear in the length of the list it is mapping on. Does it need to be this way? As a comparison, both mapM_ and map are linear in the length of the list. To wit: travis@PW:~/Documents/insurer$ ghci GHCi, version 7.0.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude> :set +s Prelude> :set +t Prelude> :m Data.List Data.Maybe Prelude Data.List Data.Maybe> foldl' (+) 0 $ fromJust $ mapM (\x -> Just x) [1..500000] 125000250000 it :: Integer (2.23 secs, 112875864 bytes) Prelude Data.List Data.Maybe> foldl' (+) 0 $ fromJust $ mapM (\x -> Just x) [1..1000000] 500000500000 it :: Integer (6.86 secs, 214002204 bytes) Prelude Data.List Data.Maybe> foldl' (+) 0 $ fromJust $ mapM (\x -> Just x) [1..2000000] 2000001000000 it :: Integer (24.39 secs, 429299748 bytes) Prelude Data.List Data.Maybe> foldl' (+) 0 $ map (\x -> x - 1) [1..1000000] 499999500000 it :: Integer (0.77 secs, 171213436 bytes) Prelude Data.List Data.Maybe> foldl' (+) 0 $ map (\x -> x - 1) [1..10000000] 49999995000000 it :: Integer (7.42 secs, 1723399472 bytes) Prelude Data.List Data.Maybe> foldl' (+) 0 $ map (\x -> x - 1) [1..40000000] 799999980000000 it :: Integer (30.46 secs, 6894835952 bytes) Prelude Data.List Data.Maybe> mapM_ (\x -> Just x) [1..1000000] Just () it :: Maybe () (0.42 secs, 82761248 bytes) Prelude Data.List Data.Maybe> mapM_ (\x -> Just x) [1..10000000] Just () it :: Maybe () (3.87 secs, 808012660 bytes) Prelude Data.List Data.Maybe> mapM_ (\x -> Just x) [1..100000000] Just () it :: Maybe () (38.40 secs, 8054769564 bytes) Prelude Data.List Data.Maybe>

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Next European Hackathon
by Christopher Done 08 Sep '11

08 Sep '11

‘Ello! Any plans for the next European hackathon location that will presumably be in 6~ months? I need time to reap potential participants. Wonder if we could arrange an Italian hackathon? Verohac? Hm. :-) Maybe Utrecht? Hac6? Ciao!

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