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ANN: Cabal v1.18.0 released
by Johan Tibell 04 Sep '13

04 Sep '13

Hi all, On behalf of the cabal maintainers and contributors I'm proud to announce the Cabal (and cabal-install) 1.18.0 release. To install run cabal update && cabal install Cabal-1.18.0 cabal-install-1.18.0 With 854 commits since the last release there are two many improvements and bug fixes to list them here, but two highlights are: * Hermetic builds using sandboxes. This should reduce the number of "dependency hell" and broken package DB problems. * GHCi support. It's now much easier to use ghci when developing your packages, especially if those packages require preprocessors (e.g. hsc2hs). Here's how working on a package might look like using the new features: # Only once: cabal sandbox init cabal install --only-dependencies --enable-tests # Configure, build, and run tests: cabal test # now implies configure and build # Play around with the code in GHCi: cabal repl Mikhail wrote a bit more about the user visible changes on his blog: http://coldwa.st/e/blog/2013-08-21-Cabal-1-18.html For a complete list of changes run git log cabal-install-v1.16.0.2..cabal-install-v1.18.0 in the cabal repo or look at the GitHub compare page: https://github.com/haskell/cabal/compare/cabal-install-v1.16.0.2...cabal-in… (only shows the last 250 commits). 57 people contributed to this release! 503 Mikhail Glushenkov 99 Johan Tibell 41 Duncan Coutts 39 Ian Lynagh 19 Brent Yorgey 19 Thomas Tuegel 18 Ben Millwood 16 Eyal Lotem 10 Thomas Dziedzic 7 Andres Loeh 6 John Wiegley 6 Benno Fünfstück 5 Gregory Collins 4 Herbert Valerio Riedel 4 Simon Hengel 3 Joachim Breitner 3 Luke Iannini 3 Bryan Richter 3 Richard Eisenberg 3 Tuncer Ayaz 3 Jens Petersen 2 Arun Tejasvi Chaganty 2 Bryan O'Sullivan 2 Eric Kow 2 Jookia 2 Paolo G. Giarrusso 2 Paolo Capriotti 1 Sönke Hahn 1 Yitzchak Gale 1 Albert Krewinkel 1 stepcut 1 Alexander Kjeldaas 1 Austin Seipp 1 Bardur Arantsson 1 Ben Doyle 1 Ben Gamari 1 Bram 1 Carter Tazio Schonwald 1 Clint Adams 1 Daniel Wagner 1 David Lazar 1 Erik Hesselink 1 Eugene Sukhodolin 1 Gabor Greif 1 Jack Henahan 1 Jason Dagit 1 Ken Bateman 1 Mark Lentczner 1 Masahiro Yamauchi 1 Merijn Verstraaten 1 Michael Thompson 1 Niklas Hambüchen 1 Oleksandr Manzyuk 1 Patrick Premont 1 Roman Cheplyaka 1 Sergei Trofimovich 1 Stephen Blackheath -- Johan, on behalf of the cabal maintainers and contributors.

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ANN: set-cover solves Sudoku, Soma cube, 8 Queens etc.
by Henning Thielemann 04 Sep '13

04 Sep '13

I have prepared the package set-cover for solving exact set cover problems. It includes example programs for solving Sudoku, 8 Queens, Soma Cube, Tetris Cube, Cube of L's, and Logika's Baumeister puzzle. Please refer to these examples for learning how the library works. The solver is generic with respect to the representation of sets. You may either use the high-level Set type from containers package or low-level bit vectors. http://hackage.haskell.org/package/set-cover The package is simple Haskell 2010.

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AVICPS 2013: Call for Papers. Submission deadline Sep 23, 2013
by CAV 2012 CFP 04 Sep '13

04 Sep '13

-------------------------------------------------------------------------------------- AVICPS 2013 The 4th Analytic Virtual Integration of Cyber-Physical Systems Workshop http://www.analyticintegration.org/ Vancouver, Canada, December 3, 2013. (Co-located with RTSS 2013) *** Paper Submission: September 23, 2013 *** CALL FOR PAPERS The Analytic Virtual Integration Cyber-Physical Systems (AVICPS) workshop focuses on analytic techniques that enable the early discovery of faults in CPS before the system is integrated or its parts are built. Such an approach is known as analytic virtual integration. The objective is to discover and resolve problems early during the design and implementation phases where cost impact is low. Topics of interest include, but are not limited to: * A quantitative and early analysis of end-to-end system architecture performance that incorporates realistic hardware details (e.g. multi-core, memory architectures, I/O, network-on-chip, etc.) and workloads (e.g. video streams, weather data, GPS, critical messages, etc.) * Fault tolerance technologies for handling the combination of faults in computing and communication hardware and software and physical system disturbances. * Safety analysis such as model checking for mixed criticality CPS applications (e.g., flight management systems and safe interoperability of medical devices). * System level optimization technologies that support the combinatorial optimization of task scheduling and allocation, I/O, and network traffic routing. * Security protocol development and verification techniques for CPS applications. * Modeling, simulation, and verification techniques for virtual integration. * Models for describing or quantifying the environment that systems must operate in. * Quantitative measurements of the advantages of virtual integration. * Formal methods for defining and reasoning about internal and external interfaces of the system and its parts. * Cross-domain compositional theories and technologies for CPS. SUBMISSION The AVICPS workshop welcomes original contributions on theoretical foundation, tools, and evaluations. Of particular interest are case studies on challenges of expressing properties of systems in terms of their components and the architecture that governs their interactions. Both solutions and open problems are welcome. Researchers and practitioners are encouraged to submit two types of papers: * Research papers that present novel ideas, mature tools, results, and advancement of the state-of-the-art. * Position papers that describe ongoing work, less mature work, or new research directions. Submissions should be no more than 8 pages (for research papers) and 4 pages (for position papers) in two-column format. Templates and author guidelines are available for LaTeX and Microsoft Word. All figures and references must fit within the specified page limits. PUBLICATION Authors of accepted papers may choose one of the following alternatives. * To include their paper in formal electronic proceedings published by LiU Electronic Press. The proceedings are given both ISBN and ISSN numbers. Authors retain the copyright of their work. * To not include it in the proceedings, thus make it possible to refine and submit the work elsewhere. Only a title and a short abstract of the paper will be available in the proceedings. An informal copy of the accepted paper will be available on the AVICPS website. Regardless of the author's choice of dissemination, the reviewing process and the presentation time at the workshop will be the same. For all accepted papers, at least one of the authors must register and present the paper at the workshop. IMPORTANT DATES Paper Submission: Sep. 23, 2013 Author Notification: Oct. 28, 2013 Camera Ready: Nov. 10, 2013 AVICPS Workshop: Dec. 3, 2013 WORKSHOP ORGANIZATION Program Co-Chairs * David Broman. UC Berkeley, USA, and Linkoping University, Sweden * Gabor Karsai. Vanderbilt University, USA Program Committee Manfred Broy, Technical University Munich, Germany Eric Feron, Georgia Institute of Technology, USA Peter Fritzson, Linkoping University, Sweden Jerome Hugues, ISAE, France Mirko Jakovljevic, TTTech, Austria Russell Kegley, Lockheed Martin, USA Doo-Hyun Kim, Konkuk University, South Korea Henrik Nilsson, University of Nottingham, UK Roman Obermaisser, University of Siegen, Germany Jim Paunicka, Boeing, USA Andre Platzer, Carnegie Mellon, USA Linh Thi Xuan Phan, University of Pennsylvania, USA Franz Rammig, Univerity of Paderborn, Germany Walid Taha, Halmstad University, Sweden Stavros Tripakis, University of California, Berkeley, USA Shige Wang, GM Research, USA Michael Whalen, University of Minnesota, USA Dirk Zimmer, DLR Oberpfaffenhofen, Germany For further information, including submission guidelines, see the AVICPS Workshop website: http://www.analyticintegration.org/

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PPDP 2013 + LOPSTR 2013 Call for participation
by Ricardo Peña 30 Aug '13

30 Aug '13

(Apologies for multiple copies of this announcement) CALL FOR PARTICIPATION: ========================================================= PPDP 2013 15th International Symposium on Principles and Practice of Declarative Programming Madrid, Spain, September 16-18, 2013 http://users.ugent.be/~tschrijv/PPDP2013/ and LOPSTR 2013 23rd International Symposium on Logic-Based Program Synthesis and Transformation Madrid, Spain, September 18-19, 2013 http://www.utdallas.edu/~gupta/lopstr/ ========================================================= Registration is open now. There is a significant discount if you register for both events. Registration link: http://dalila.sip.ucm.es/ppdp-lopstr-13/?page_id=31 You can access the PPDP 2013 scientific program at: http://users.ugent.be/~tschrijv/PPDP2013/program.pdf You can access the LOPSTR 2013 scientific program at: http://www.utdallas.edu/~gupta/lopstr/lopstr-program.pdf Hope to see you at Madrid

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ANN: Chart library v1.0
by Tim Docker 29 Aug '13

29 Aug '13

I'm pleased to announce version 1.0 of the Chart library - a library for rendering 2D charts in haskell. It supports a variety of plot types, and several different rendering backends. Whilst the library has seen sporadic patches and releases in recent years, development has seen a huge spike over the last 3 months thanks to Jan Bracker's excellent GSOC work. The key changes in this release are: * The rendering backend has been abstracted, and there are rendering implementations for cairo and the diagrams library. The removal of the dependency on cairo should make the chart library more useful to haskell developers on windows and OSX. Jan Bracker has put a huge effort into this change. * The library has switched from using data-accessor to lenses to provide accessors for the plotting data model. Thanks to Ben Gamari for this change. These, along with various other API changes justify a 1.0 version. Details of the library and code examples can be found on the github wiki: https://github.com/timbod7/haskell-chart/wiki The packages and API documentation are on hackage: http://hackage.haskell.org/package/Chart http://hackage.haskell.org/package/Chart-cairo http://hackage.haskell.org/package/Chart-diagrams Tim Docker

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Haskell Weekly News: Issue 278
by Daniel Santa Cruz 29 Aug '13

29 Aug '13

Welcome to issue 278 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of August 18 to 24, 2013. Quotes of the Week * johnw: finger trees must be related to palm trees somehow * monochrom: "do, or undo. there is no redo." :) * danharaj: arrows are just strong monads in the 2-category of profunctors. what's the problem? * BMeph: If only they knew the POWER...of the darcs-IDE! * geekosaur: "tekmo and the pipes list" sounds like some kind of postmodernist band Top Reddit Stories * Building an Asteroids Clone in Haskell using Netwire Domain: ocharles.org.uk, Score: 88, Comments: 22 On Reddit: [1] http://goo.gl/HZBtcK Original: [2] http://goo.gl/Gp8TVw * What's new in Cabal 1.18 - sandboxes, REPL, cross-compilation and more! Domain: coldwa.st, Score: 75, Comments: 18 On Reddit: [3] http://goo.gl/8eSChe Original: [4] http://goo.gl/VrHkMY * An Introduction to Cabal sandboxes Domain: coldwa.st, Score: 64, Comments: 33 On Reddit: [5] http://goo.gl/oFGzfK Original: [6] http://goo.gl/ByA6Ru * Reasoning about space leaks with space invariants Domain: apfelmus.nfshost.com, Score: 59, Comments: 48 On Reddit: [7] http://goo.gl/cKlPrM Original: [8] http://goo.gl/E4kIjD * Bound: Making de Bruijn Succ Less on School of Haskell by Edward Kmett Domain: fpcomplete.com, Score: 48, Comments: 14 On Reddit: [9] http://goo.gl/v7tgWO Original: [10] http://goo.gl/glTA3N * PatternSynonyms - ghc trac Domain: ghc.haskell.org, Score: 35, Comments: 14 On Reddit: [11] http://goo.gl/8zuy1T Original: [12] http://goo.gl/5Bw6FN * Revisiting Matrix Multiplication, Part III: Customizing Vector by Edward Kmett Domain: fpcomplete.com, Score: 33, Comments: 1 On Reddit: [13] http://goo.gl/hfoJJ7 Original: [14] http://goo.gl/yLUSWP * Great new platform to increase *practical* code literacy (with Haskell support). Domain: mdswanson.com, Score: 29, Comments: 13 On Reddit: [15] http://goo.gl/sFLBQm Original: [16] http://goo.gl/TIJPTi * Bartosz' basic Haskell: Error Handling Domain: fpcomplete.com, Score: 28, Comments: 4 On Reddit: [17] http://goo.gl/1jBaWG Original: [18] http://goo.gl/zZrPxH * A Pragmatic Case for Static Typing with Brian Hurt on Vimeo (at NY-Haskell) Domain: vimeo.com, Score: 27, Comments: 11 On Reddit: [19] http://goo.gl/uECaaB Original: [20] http://goo.gl/59c8Wo * Write yourself a Brainfuck in an hour Domain: github.com, Score: 26, Comments: 13 On Reddit: [21] http://goo.gl/lAfzRf Original: [22] http://goo.gl/cbJZ7t Top StackOverflow Questions * Is it possible to lazily traverse a recursive data-structure with O(1) memory usage, tail-call optimized? votes: 10, answers: 4 Read on SO: [23] http://goo.gl/1qsBKq * pattern matching of the form: Option{..} <- votes: 10, answers: 1 Read on SO: [24] http://goo.gl/HY3FWY Until next time, [25]+Daniel Santa Cruz References 1. http://ocharles.org.uk/blog/posts/2013-08-18-asteroids-in-netwire.html 2. http://www.reddit.com/r/haskell/comments/1kmes7/building_an_asteroids_clone… 3. http://coldwa.st/e/blog/2013-08-21-Cabal-1-18.html 4. http://www.reddit.com/r/haskell/comments/1kslyi/whats_new_in_cabal_118_sand… 5. http://coldwa.st/e/blog/2013-08-20-Cabal-sandbox.html 6. http://www.reddit.com/r/haskell/comments/1kpynl/an_introduction_to_cabal_sa… 7. http://apfelmus.nfshost.com/blog/2013/08/21-space-invariants.html 8. http://www.reddit.com/r/haskell/comments/1ksu0v/reasoning_about_space_leaks… 9. https://www.fpcomplete.com/user/edwardk/bound 10. http://www.reddit.com/r/haskell/comments/1knvz2/bound_making_de_bruijn_succ… 11. http://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms 12. http://www.reddit.com/r/haskell/comments/1kmods/patternsynonyms_ghc_trac/ 13. https://www.fpcomplete.com/user/edwardk/revisiting-matrix-multiplication-pa… 14. http://www.reddit.com/r/haskell/comments/1kmvs2/revisiting_matrix_multiplic… 15. http://mdswanson.com/blog/2013/08/19/how-to-practice-code-reviews.html 16. http://www.reddit.com/r/haskell/comments/1krc6t/great_new_platform_to_incre… 17. https://www.fpcomplete.com/user/bartosz/basics-of-haskell/10_Error_Handling 18. http://www.reddit.com/r/haskell/comments/1ksjt4/bartosz_basic_haskell_error… 19. https://vimeo.com/72870631 20. http://www.reddit.com/r/haskell/comments/1kusbt/a_pragmatic_case_for_static… 21. https://github.com/quchen/articles/blob/master/write_yourself_a_brainfuck.md 22. http://www.reddit.com/r/haskell/comments/1kz39d/write_yourself_a_brainfuck_… 23. http://stackoverflow.com/questions/18345734/is-it-possible-to-lazily-traver… 24. http://stackoverflow.com/questions/18372188/pattern-matching-of-the-form-op… 25. https://plus.google.com/105107667630152149014/about

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please improve this code - thanks
by Me 24 Aug '13

24 Aug '13

Hi all. I'm new to haskell. I have a puny piece of code: import Data.List.Split padL :: Int -> String -> String padL n s | length s < n = replicate (n - length s) '0' ++ s | otherwise = s strInc :: String -> String -> String strInc sep str = let strarr = splitOn sep str zprefix = strarr !! 0 znumber = strarr !! 1 in zprefix ++ sep ++ padL ( length (znumber) ) ( show ( read ( znumber ) + 1 ) ) Prelude> :l strinc [1 of 1] Compiling Main ( strinc.hs, interpreted ) Ok, modules loaded: Main. *Main> strInc "-" "xs-00009" "xs-00010" *Main> strInc "<>" "yxs<>000099" "yxs<>000100" Is it good haskell, bad haskell or average haskell? How can it be rewritten? Thanks.

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Haskell Weekly News: Issue 277
by Daniel Santa Cruz 22 Aug '13

22 Aug '13

Welcome to issue 277 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of August 11 to 17, 2013. Quotes of the Week * psygnisfive: Seminearring is the task of giving seminars. * Taneb: You know you've made it when SPJ asks you for help with Haskell. * byorgey: . o O ( "For my next trick, I will CPS-encode this rabbit!" -- edwardk ) * shachaf: I prefer the cogolden rule: When CPS-transforming, doubt. * edwardk: "You see these scars? I got them back in 7.7." * danharaj: parsing is hard, let's go shopping Top Reddit Stories * Mio: A High-Performance Multicore IO Manager for GHC [pdf] Domain: haskell.cs.yale.edu, Score: 147, Comments: 31 On Reddit: [1] http://goo.gl/ZTy1Yl Original: [2] http://goo.gl/6foNWC * Destroying Performance with Strictness Domain: neilmitchell.blogspot.ru, Score: 92, Comments: 45 On Reddit: [3] http://goo.gl/1rkx3a Original: [4] http://goo.gl/rb5UnM * A great series of posts on the power of monoids Domain: self.haskell, Score: 78, Comments: 10 On Reddit: [5] http://goo.gl/TmAAwT Original: [6] http://goo.gl/TmAAwT * Cellular Automata by Edward Kmett Domain: fpcomplete.com, Score: 69, Comments: 7 On Reddit: [7] http://goo.gl/EIFK5A Original: [8] http://goo.gl/03mNhV * Elm 0.9 - New type checker, much better error messages Domain: elm-lang.org, Score: 50, Comments: 14 On Reddit: [9] http://goo.gl/ngSBPX Original: [10] http://goo.gl/4Jp3l6 * Revisiting Matrix Multiplication, Part I by Edward Kmett Domain: fpcomplete.com, Score: 45, Comments: 4 On Reddit: [11] http://goo.gl/gYfm5S Original: [12] http://goo.gl/bg75ZX * Revisiting Matrix Multiplication, Part II by Edward Kmett Domain: fpcomplete.com, Score: 37, Comments: 9 On Reddit: [13] http://goo.gl/qU2r69 Original: [14] http://goo.gl/5cRq72 * Roles: a new feature of GHC (patch GND + type families) Domain: typesandkinds.wordpress.com, Score: 34, Comments: 28 On Reddit: [15] http://goo.gl/HhVOTu Original: [16] http://goo.gl/Twx5YB * Type Inference, Haskell and Dependent Types :: PDF Domain: personal.cis.strath.ac.uk, Score: 33, Comments: 0 On Reddit: [17] http://goo.gl/MbtYGO Original: [18] http://goo.gl/uOx01F * Embedded Languages for High-Performance Computing [Chakravarty, PDF 70 slides] Domain: speakerdeck.com, Score: 31, Comments: 4 On Reddit: [19] http://goo.gl/mb2frN Original: [20] http://goo.gl/EEG0Wk * Graph drawing with gloss Domain: mazzo.li, Score: 30, Comments: 7 On Reddit: [21] http://goo.gl/j0CZmo Original: [22] http://goo.gl/5ZtFuu * Benchmarking sqlite-simple against Python and C Domain: nurpax.github.io, Score: 28, Comments: 9 On Reddit: [23] http://goo.gl/CNyjWa Original: [24] http://goo.gl/gFmWgT * What is "lifting"? Explained on stackoverflow Domain: stackoverflow.com, Score: 25, Comments: 7 On Reddit: [25] http://goo.gl/HzXWb9 Original: [26] http://goo.gl/hQxTce * GHC API: Interpreted, compiled and package modules Domain: parenz.wordpress.com, Score: 23, Comments: 0 On Reddit: [27] http://goo.gl/xUeUYq Original: [28] http://goo.gl/llQsyE * Time to start writing on the new binding: SDL 2.0 release. Domain: lists.libsdl.org, Score: 22, Comments: 15 On Reddit: [29] http://goo.gl/G0ut36 Original: [30] http://goo.gl/MuO1uB * FP Complete's Haskell programming competition now accepting entries Domain: fpcomplete.com, Score: 21, Comments: 7 On Reddit: [31] http://goo.gl/tbEBKG Original: [32] http://goo.gl/ADsrJ * Pretext by experiments and guesses Domain: fpcomplete.com, Score: 18, Comments: 15 On Reddit: [33] http://goo.gl/oVpKIe Original: [34] http://goo.gl/2PFthz Top StackOverflow Questions * Haskell random numbers suddenly start to “converge” after months of running votes: 30, answers: 1 Read on SO: [35] http://goo.gl/oxUAQ5 * Why does ghc generate so many useless-looking nested case expressions? votes: 10, answers: 1 Read on SO: [36] http://goo.gl/6cdTd1 Until next time, [37]+Daniel Santa Cruz References 1. http://haskell.cs.yale.edu/wp-content/uploads/2013/08/hask035-voellmy.pdf 2. http://www.reddit.com/r/haskell/comments/1k6fsl/mio_a_highperformance_multi… 3. http://neilmitchell.blogspot.ru/2013/08/destroying-performance-with-strictn… 4. http://www.reddit.com/r/haskell/comments/1ker84/destroying_performance_with… 5. http://www.reddit.com/r/haskell/comments/1ka4q6/a_great_series_of_posts_on_… 6. http://www.reddit.com/r/haskell/comments/1ka4q6/a_great_series_of_posts_on_… 7. https://www.fpcomplete.com/user/edwardk/cellular-automata 8. http://www.reddit.com/r/haskell/comments/1kj5zh/cellular_automata_by_edward… 9. http://elm-lang.org/blog/announce/version-0.9.elm 10. http://www.reddit.com/r/haskell/comments/1ka0ld/elm_09_new_type_checker_muc… 11. https://www.fpcomplete.com/user/edwardk/revisiting-matrix-multiplication-pa… 12. http://www.reddit.com/r/haskell/comments/1kecqt/revisiting_matrix_multiplic… 13. https://www.fpcomplete.com/user/edwardk/revisiting-matrix-multiplication-pa… 14. http://www.reddit.com/r/haskell/comments/1khu61/revisiting_matrix_multiplic… 15. http://typesandkinds.wordpress.com/2013/08/15/roles-a-new-feature-of-ghc/ 16. http://www.reddit.com/r/haskell/comments/1kgivs/roles_a_new_feature_of_ghc_… 17. https://personal.cis.strath.ac.uk/adam.gundry/thesis/ 18. http://www.reddit.com/r/haskell/comments/1k6g0w/type_inference_haskell_and_… 19. https://speakerdeck.com/mchakravarty/embedded-languages-for-high-performanc… 20. http://www.reddit.com/r/haskell/comments/1kc9j1/embedded_languages_for_high… 21. http://mazzo.li/posts/graph-drawing.html 22. http://www.reddit.com/r/haskell/comments/1kb36j/graph_drawing_with_gloss/ 23. http://nurpax.github.io/posts/2013-08-17-sqlite-simple-benchmarking.html 24. http://www.reddit.com/r/haskell/comments/1kjpwz/benchmarking_sqlitesimple_a… 25. http://stackoverflow.com/questions/2395697/haskell-newbie-question-what-is-… 26. http://www.reddit.com/r/haskell/comments/1k7i4c/what_is_lifting_explained_o… 27. http://parenz.wordpress.com/2013/08/17/ghc-api-interpreted-compiled-and-pac… 28. http://www.reddit.com/r/haskell/comments/1kjl3h/ghc_api_interpreted_compile… 29. http://lists.libsdl.org/pipermail/sdl-libsdl.org/2013-August/089854.html 30. http://www.reddit.com/r/haskell/comments/1k9wh8/time_to_start_writing_on_th… 31. https://www.fpcomplete.com/business/competition/competition-overview 32. http://www.reddit.com/r/haskell/comments/1k8ox7/fp_completes_haskell_progra… 33. https://www.fpcomplete.com/user/tel/pretext-by-experiments-and-guesses 34. http://www.reddit.com/r/haskell/comments/1kkoup/pretext_by_experiments_and_… 35. http://stackoverflow.com/questions/18200283/haskell-random-numbers-suddenly… 36. http://stackoverflow.com/questions/18192184/why-does-ghc-generate-so-many-u… 37. https://plus.google.com/105107667630152149014/about

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ANN: Google co-sponsoring ZuriHac 2013
by Bas van Dijk 21 Aug '13

21 Aug '13

Dear Haskellers, I would like to remind you that the Zurich FP Afternoon (with a keynote by Simon Marlow) is taking place next week (13:00, Thursday, 29 August) and is directly followed by the ZuriHac 2013 Haskell Hackathon [1]. There are still some places available at both events -- you're welcome to register at: http://bit.ly/ZuriHac2013Reg Google Switzerland will co-sponsor the FP Afternoon and ZuriHac 2013 together with ETH Zurich and Erudify. Their sponsorship means we can give each attendee a free t-shirt (picture on the wikipage [2]) and free food and drinks during the FP Afternoon. Google is also offering a quiz during the FP Afternoon with prizes including a Galaxy S4 mini. I hope to see you there! Bas [1] http://www.haskell.org/haskellwiki/ZuriHac2013 [2] http://www.haskell.org/haskellwiki/ZuriHac2013#News

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ANNOUNCE: posix-paths, for faster file system operations
by Niklas Hambüchen 21 Aug '13

21 Aug '13

John Lato and I would like to announce our posix-paths package. https://github.com/JohnLato/posix-paths It implements a large portion of System.Posix.FilePath using ByteString based RawFilePaths instead of String based FilePaths, and on top of that provides a Traversal module with a fast replacement for `getDirectoryContents` and a recursive `allDirectoryContents`. `getDirectoryContents` is (unsurprisingly?) really slow. Our replacement is 11 times faster in the recursive use case [1], and only 20% slower than `find`. Benchmarks are at [2], code is at [3]. We hope that these improvements will eventually make it into base some day. Until then, we propose our package as a base for discussion and further improvements. Contributions are welcome: Some FilePath operations are not in it yet (especially the Windows / drive related ones), and our traversals might not work on Windows. We would also appreciate some thorough looks at their low level implementations. If you find our benchmarks against getDirectoryContents unfair or would like to add another one, please send a pull request. We have been running this on Linux production machines for a few months now, and are pleased by the speed-up. [1] For the recursive version of the original `getDirectoryContents`, we used the implementation given in Real World Haskell: http://book.realworldhaskell.org/read/io-case-study-a-library-for-searching… [2] Benchmarks: On a real file system: http://johnlato.github.io/posix-paths/usrLocal.html On tmpfs: http://johnlato.github.io/posix-paths/tmpfs.html (note that here find is slow because of process starting overhead) [3] Code: Github: https://github.com/JohnLato/posix-paths RawFilePath operations: https://github.com/JohnLato/posix-paths/blob/master/src/System/Posix/FilePa… Traversals: https://github.com/JohnLato/posix-paths/blob/master/src/System/Posix/Direct… Benchmarks: https://github.com/JohnLato/posix-paths/blob/master/benchmarks/Bench.hs

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