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Haskell Weekly News: Issue 179
by Daniel Santa Cruz 28 Apr '11

28 Apr '11

Welcome to issue 179 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of April 16 to 23, 2011. Announcements Alex Mason announced (http://goo.gl/2qtyM) the second annual Australian Haskell Hackathon to be heald from Friday July 8th to Sunday July 10th, at the UNSW's Computer Science building in Sydney. Come share with your fellow Australasian Haskellers! "The Hac" team invited us (http://goo.gl/8EQfI) to HacPhi 2011, a Haskell hackathon/get-together to be held July 29 to 31 at the University of Pennsylvania, in Philadelphia. Daniel Wagner wanted to stress that "everyone is welcome--you do not have to be a Haskell guru. Helping hack on someone else's project could be a great way to increase your Haskell-fu." Robert Clausecker asked "Is Hugs dead?" (http://goo.gl/639dC) Sad to see projects of this sort fade into the past. Quotes of the Week * copumpkin: THE POWER OF MIXFIX COMPELS YOU (to not use it much) Top Reddit Stories * Why Darcs users care about consistency Domain: koweycode.blogspot.com, Score: 59, Comments: 3 On Reddit: http://goo.gl/oBU0r Original: http://goo.gl/lnUCU * Review: Learn You a Haskell for Great Good! Domain: jerf.org, Score: 57, Comments: 15 On Reddit: http://goo.gl/BjJq7 Original: http://goo.gl/P7u3x * The Haskell Heap : Inside P4 Domain: blog.ezyang.com, Score: 37, Comments: 3 On Reddit: http://goo.gl/EoV5D Original: http://goo.gl/ropku * First-class modules for Haskell : Shields and Peyton Jones, 2001 :: PDF Domain: research.microsoft.com, Score: 27, Comments: 1 On Reddit: http://goo.gl/7renV Original: http://goo.gl/7lHV4 * Darcs hacking sprint 6 report Domain: blog.darcs.net, Score: 27, Comments: 13 On Reddit: http://goo.gl/ljO1O Original: http://goo.gl/xRr6r * Ugly memoization Domain: augustss.blogspot.com, Score: 25, Comments: 8 On Reddit: http://goo.gl/D6FoV Original: http://goo.gl/IUL1M * Monoids for Maybe Domain: byorgey.wordpress.com, Score: 23, Comments: 2 On Reddit: http://goo.gl/yVU7O Original: https://byorgey.wordpress.com/2011/04/18/monoids-for-maybe/ * Don't forget to think about GC flags when doing performance tuning Domain: stackoverflow.com, Score: 20, Comments: 3 On Reddit: http://goo.gl/6xzEj Original: http://goo.gl/Xwkro * Haskell videos on video.google.com, which shuts down for good on April 29th 2011 Domain: google.com, Score: 20, Comments: 5 On Reddit: http://goo.gl/MizlZ Original: http://goo.gl/CxnBK * Evaluation on the Haskell Heap Domain: blog.ezyang.com, Score: 20, Comments: 2 On Reddit: http://goo.gl/EX5aE Original: http://goo.gl/cU7Nt Top StackOverflow Questions * What are the primary theoretical difficulties with adding ML-style modules to Haskell? votes: 27, answers: 3 Read on SO: http://goo.gl/8An0y * Optimizing numerical array performance in Haskell votes: 25, answers: 1 Read on SO: http://goo.gl/ykzlV * lenses, fclabels, data-accessor - which library for structure access and mutation is better votes: 17, answers: 1 Read on SO: http://goo.gl/c74uO * In Haskell performing 'and' and 'or' for boolean functions votes: 15, answers: 5 Read on SO: http://goo.gl/0U5pI * Automatic memoizing in functional programming languages votes: 11, answers: 4 Read on SO: http://goo.gl/hg8Ei * Alternative implementations of Haskell's standard library type classes votes: 9, answers: 3 Read on SO: http://goo.gl/LDp9u * Scheme vs Haskell for an Introduction to Functional Programming? [migrated] votes: 8, answers: 0 Read on SO: http://goo.gl/lbeX3 * Writing loops for interactive IO: problems with do-notation and layout votes: 5, answers: 1 Read on SO: http://goo.gl/HVRrR * Python-"is"-like equality operator for Haskell/GHC votes: 5, answers: 4 Read on SO: http://goo.gl/7Z4mA * Optimising a Haskell XML parser votes: 5, answers: 1 Read on SO: http://goo.gl/fsqqw About the Haskell Weekly News To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. Until next time, Daniel Santa Cruz

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REMINDER: Haskell Communities and Activities Report, May 2011 edition
by Janis Voigtländer 27 Apr '11

27 Apr '11

Dear all, It is not yet too late to contribute to the 20th edition of the ================================================================ Haskell Communities & Activities Report http://tinyurl.com/haskcar Submission deadline: this weekend (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ================================================================ If you haven't already, please write an entry for your new project or update your old entry. More information can be found in the original Call for Contributions at http://www.haskell.org/pipermail/haskell/2011-April/022720.html I look forward to your contributions, Janis (current editor) -- Jun.-Prof. Dr. Janis Voigtländer http://www.iai.uni-bonn.de/~jv/ mailto:jv@iai.uni-bonn.de

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ANNOUNCE: New version Feldspar
by Emil Axelsson 27 Apr '11

27 Apr '11

On behalf of the Feldspar team, I'm happy to announce version 0.4.0.2 of feldspar-language and feldspar-compiler: http://hackage.haskell.org/package/feldspar-language http://hackage.haskell.org/package/feldspar-compiler Feldspar is an embedded domain-specific language for generating code for embedded applications, in particular for digital signal processing. For more information, see our web pages: http://feldspar.inf.elte.hu/feldspar/ http://feldspar.inf.elte.hu/ A brief list of changes since the last version: * Support for GHC 7. * Including a fresh tutorial for new users. * Improved C code generation (efficiency and readability). - Efficient vector append. - More unified representation of arrays in the C code. - Etc. * A new sequential construct for unfolding vectors using an accumulating parameter. * Support for structs. * New optimization: common sub-expression elimination. * Lots of restructuring under the hood. * Bugfixes. / Emil

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ANNOUNCE: acid-state-0.4
by Lemmih 27 Apr '11

27 Apr '11

Greetings, With acid-state-0.4, you can use regular Haskell data structures without worrying about data loss or durability. Your state will simply always be available to you even after software crashes or power outages. Acid-state-0.4 improves over the previous version by leveraging the might of 'cereal' and 'safecopy'. Those two packages provide better error handling and improved data safety. Additionally, acid-state-0.4 contains yet more examples and a handful of general wibbles. For examples of how to use the library, see: http://mirror.seize.it/acid-state/examples/ Hackage page for acid-state: http://hackage.haskell.org/package/acid-state Wiki site: http://acid-state.seize.it/ -- Cheers, Lemmih

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ANNOUNCE: iteratee-compress 0.2.0.0
by Maciej Piechotka 23 Apr '11

23 Apr '11

Iteratee-compress provides compressing and decompressing enumerators including flushing (using John Lato's implementation). Currently only gzip and bzip is provided but LZMA is planned. Changes from previous version: - Add BZip support Next goals: - LZMA support - Generic interface for flushing To think about: - Should inner iteratee be able to request flushing Regards

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ANNOUNCE: PEZ, the Potentially Excellent Zipper library
by Brandon Simmons 23 Apr '11

23 Apr '11

I'm happy to present my long-languishing-on-the-harddrive generic zipper library I'm calling pez: http://hackage.haskell.org/package/pez The library brings together the 'fclabels' and 'thrist' packages with the Typeable class to enable a zipper library that is (I hope) intuitive and requiring a minimum of boilerplate. Get it with: $ cabal install pez There is still much to do, in particular I have not looked at the performance characteristics of this approach at all, but I hope others find it interesting or useful. Please send any feature requests, or bug reports. EXAMPLE USAGE ================ First you need to enable some extensions, the first two for generating and using 'fclabels' lenses, the second for easy deriving of Typeable instances on custom types: > {-# LANGUAGE TemplateHaskell, TypeOperators, DeriveDataTypeable #-} > > module Main where > > -- import pez > import Data.Typeable.Zipper > -- for prettiness: > import Control.Arrow > import Control.Applicative Now we define a tree that we want to use in our zipper. We want it to be an instance of Typeable which we can derive, and we want 'fclabels' lenses to be generated with TH for the branches, so we name the records with underdashes (see: http://hackage.haskell.org/package/fclabels ) > data Tree a = Node { > _leftNode :: Tree a, > _val :: a, > _rightNode :: Tree a } > | Nil > deriving (Typeable,Show) > > $(mkLabelsNoTypes [''Tree]) At this point we can use all of our zipper functions on the Tree type. The following returns the value at the left-most Node, along with a SavedPath back to that Node. It returns Nothing if the tree is empty: > -- 'a' must be Typeable because we actually "moveTo" it here: > getLeftmost :: Typeable a=> Tree a -> Maybe (a, SavedPath (Tree a) a) > getLeftmost = fmap (viewf &&& save) . descendLeft . zipper > where descendLeft z = > case viewf z of > Nil -> moveTo val <$> moveUp 1 z > _ -> descendLeft $ moveTo leftNode z A `SavedPath` can be restored moving the focus back to the location it points to, or it can be collapsed into a lens itself. Let's use the function we defined above to make sure it works: > tree = Node (Node Nil 'a' Nil) 'b' (Node Nil 'c' Nil) > > main = do > putStr "This should show 'a': " > putStrLn $ maybe "FAIL" (show . fst) $ getLeftmost tree You can also experiment with "zipping through" computations. It's as simple as defining a new fclabel lens for a reversible computation, e.g.: > reversible :: (Show b, Read b) => b :-> String > reversible = lens show (const . read) Thanks, Brandon Simmons http://coder.bsimmons.name

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ANN: hledger 0.14
by Simon Michael 22 Apr '11

22 Apr '11

I'm pleased to announce hledger 0.14. This release includes work by Dmitry Astapov, Eric Kow, Max Bolingbroke, Omari Norman and myself. Thanks especially to Dmitry for helping me with release wrangling. binaries for linux, mac, windows: http://hledger.org/DOWNLOADS.html (64-bit linux binaries to follow) or: cabal update && cabal install hledger, cabal install hledger- web, ... home and docs: http://hledger.org irc: irc://irc.freenode.net/#ledger Release notes: * remove the specific process dependency that caused too many cabal install problems * treat arguments as possibly-encoded platform strings, do not assume UTF-8 * hledger now always reads and writes data as UTF-8, ignoring the system locale (#34) * look at the LEDGER_FILE env var for the journal path, otherwise LEDGER, like ledger * handle a blank LEDGER_FILE or LEDGER value more gracefully (use the default file path) * the default journal file path is now ~/.hledger.journal, to avoid breaking mac filevault (#41) * amounts with different prices are now aggregated, like ledger * zero amounts now have no sign or commodity, like ledger * parsing: assume current year when transaction dates have no year and there is no default year * parsing: more careful validation of eg leap years in transaction dates * parsing: better international number format support, allowing comma as decimal point and flexible digit groups (#32) * parsing: support @@ syntax specifying total price * parsing: infer the conversion price in transactions involving two unpriced commodities * parsing: support per-posting cleared status * parsing: more reporting interval syntax: biweekly, bimonthly, every N days/weeks/months/quarters/years, every Nst/nd/rd/th day of month/week * add: avoid offering account names for completion in inappropriate contexts * add: remember default account even if user submits a different amount. * convert: account-field directive specifies a field containing the base account name * convert: effective-date-field directive specifies a field containing the effective date * convert: date-format directive specifies custom date formats * convert: allow amount fields containing "AMT @@ PRICE" * histogram: honour the specified start or end dates * print: don't show a trailing space when description is blank * web: allow filter patterns with spaces if quoted, like command line * web: make edit form more cross-browser compatible, fixing it in firefox (#38) * web: move hidden add/edit/import forms below main content to help text-mode browsers a bit (#33) Release contributors: Simon Michael, Dmitry Astapov, Eric Kow, Max Bolingbroke, Omari Norman. Stats: 137 days, 113 commits, 11 end-user features and 15 end-user bugfixes since last release. 189 unit & functional tests and 59% unit test coverage (hledger, hledger-lib packages). 5540 lines of code (all packages). Cheers, -Simon

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ANN: HacPhi 2011
by Daniel Wagner 21 Apr '11

21 Apr '11

Greetings, I am very pleased to officially announce HacPhi 2011, a Haskell hackathon/get-together to be held July 29-31 at the University of Pennsylvania in Philadelphia supported by contributions from Amgen, Jane Street, and Microsoft Research. The hackathon will officially kick off at 2:30 Friday afternoon, and go until 5pm on Sunday (with breaks for sleep, of course). Last year's HacPhi was a lot of fun, drawing an international crowd, and many people have already expressed interest in coming back this year. Come meet your Haskelly brothers-in-arms! I want to stress that everyone is welcome---you do not have to be a Haskell guru. Helping hack on someone else's project could be a great way to increase your Haskell-fu. If you plan on coming, please officially register [1]. Registration, travel, lodging and many other details can be found on the HacPhi wiki [2]. We're also looking for a few people interested in giving short (15-20 min.) talks, probably on Saturday afternoon. Anything of interest to the Haskell community is fair game---a project you've been working on, a paper, a quick tutorial. If you'd like to give a talk, add it on the wiki [3]. Hope to see you in Philadelphia! - The Hac φ team Brent Yorgey (byorgey) Daniel Wagner (dmwit) Chris Casinghino (ccasin) [1] http://haskell.org/haskellwiki/Hac_φ/Register [2] http://haskell.org/haskellwiki/Hac_φ [3] http://haskell.org/haskellwiki/Hac_φ/Talks

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Haskell Weekly News: Issue 178
by Daniel Santa Cruz 21 Apr '11

21 Apr '11

Welcome to issue 178 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of April 10 to 16, 2011. You can find the HTML version at: http://bit.ly/feMLgB Announcements Simon Marlow commented (http://goo.gl/XythI) on plans to have a Hackathon at MSR Cambridge this summer. Dr. Heinrich Hordegen informed us (http://goo.gl/lQvqw) of the creation of a Munich funtional programmers' user group. Help us spread the word to anyone interested in functional programming in general. Eric Y. Kow announced (http://goo.gl/PYdKI) the creation of the parallel-haskell mailing list. "The group exists to bring together the various groups in the Haskell community that are working on parallelism. It is intended to provide some visibility into the various efforts and to encourage collaboration." Don Stewart announced (http://goo.gl/0nWn2) the release of the Haskell Platform 2011.2.0.1. "This release adds support for GHC 7.0.3, and significant improvements for Mac OS X users." Quotes of the Week * Gregory Collins: "Easy to use" and "high performance" don't have to be contradictory, but you shouldn't neglect the latter. * xplat: haskell is good for portability. it can run well on any sort of x86 unix, which is all there is after all. * Spockz: it's just that my first name isn't Simon so I'm not allowed to use unsafePerformIO :P * djahandarie: Category theorists are morphisms for turning cofree theorems into free theorems. * monochrom: lambdabot is partially broken and partially correct when it comes to utf-8 * mm_freak: > case analysis of syntax -> bullshit <lambdabot> True Top Reddit Stories * Simon Peyton-Jones – A Taste Of Haskell Domain: ontwik.com, Score: 57, Comments: On Reddit: http://goo.gl/fCxtx Original: http://goo.gl/4LpJQ * Really, HaskellWiki, really? Domain: i.imgur.com, Score: 43, Comments: 13 On Reddit: http://goo.gl/HTigS Original: http://i.imgur.com/fPpby.png * Haskell Platform 2011.2.0.1 is out -- major improvements for Mac users Domain: hackage.haskell.org, Score: 39, Comments: 9 On Reddit: http://goo.gl/BJWwp Original: http://goo.gl/5vbN8 * Tracing the compilation of Hello Factorial in GHC Domain: blog.ezyang.com, Score: 36, Comments: 1 On Reddit: http://goo.gl/WNA2Z Original: http://goo.gl/fsVtS * acid-state: use regular Haskell data structures without worrying about data loss or durability Domain: haskell.org, Score: 32, Comments: 5 On Reddit: http://goo.gl/2hgGj Original: http://goo.gl/tKpV2 * Persistence of Memory: persistent vs ephemeral data structures Domain: existentialtype.wordpress.com, Score: 28, Comments: 5 On Reddit: http://goo.gl/Ss70R Original: http://goo.gl/XHdJV * Bugs from using the wrong variable Domain: blog.ezyang.com, Score: 26, Comments: 11 On Reddit: http://goo.gl/x7RId Original: http://goo.gl/3HJs2 * Cost of calling Haskell from C? Domain: stackoverflow.com, Score: 20, Comments: 1 On Reddit: http://goo.gl/6OiRH Original: http://goo.gl/XfmRe * Comparing Snap and Yesod Domain: stackoverflow.com, Score: 19, Comments: 4 On Reddit: http://goo.gl/P0Gr6 Original: http://goo.gl/dvbEe * Announcing: Heist v0.5.1 Domain: snapframework.com, Score: 17, Comments: On Reddit: http://goo.gl/cIja8 Original: http://goo.gl/d7FWG Top StackOverflow Questions * Comparing Haskell's Snap and Yesod web frameworks votes: 28, answers: 4 Read on SO: http://goo.gl/AhFH5 * Haskell library for 2D drawing votes: 19, answers: 4 Read on SO: http://goo.gl/61C4e * One REPL to bind them all? votes: 19, answers: 3 Read on SO: http://goo.gl/JUFS2 * Performance considerations of Haskell FFI / C? votes: 16, answers: 4 Read on SO: http://goo.gl/tldoX * What is Haskell's style of polymorphism? votes: 13, answers: 1 Read on SO: http://goo.gl/z3JzT About the Haskell Weekly News To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. Until next time, Daniel Santa Cruz

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CFP -- SEFM'11: EXTENDED DEADLINE
by Alberto Pardo 20 Apr '11

20 Apr '11

CALL FOR PAPERS - SEFM 2011 The 9th International Conference on SOFTWARE ENGINEERING AND FORMAL METHODS (SEFM) 14-18 November 2011 Montevideo, Uruguay URL: http://www.fing.edu.uy/inco/eventos/SEFM2011 +++++++++++++++++++++++++++++++++++++++++++++++++++ IMPORTANT DATES (EXTENDED DEADLINES) * NEW Title and abstract submission deadline: 30 April 2011 * NEW Paper submission deadline: 9 May 2011 * Acceptance/rejection notification: 15 June 2011 * Camera-ready version due: 15 July 2011 +++++++++++++++++++++++++++++++++++++++++++++++++++ BACKGROUND AND OBJECTIVES The aim of the conference is to bring together practitioners and researchers from academia, industry and government to advance the state of the art in formal methods, to facilitate their uptake in the software industry and to encourage their integration with practical engineering methods. Papers that combine formal methods and software engineering are especially welcome. Authors are invited to submit original research or tool papers on any relevant topic. These can either be normal or short papers. Short papers can discuss new ideas which are at an early stage of development and which have not yet been thoroughly evaluated. TOPICS Topics of interest include, but are not limited to: * formal requirement analysis, specification and design * programming languages, program analysis and type theory * formal methods for service-oriented and cloud computing * formal aspects of security and mobility * model checking, theorem proving and decision procedures * formal methods for real-time, hybrid and embedded systems * formal methods for safety-critical, fault-tolerant and secure systems * software architecture and coordination languages * component, object and multi-agent systems * formal aspects of software evolution and maintenance * formal methods for testing, re-engineering and reuse * light-weight and scalable formal methods * tool integration * applications of formal methods, industrial case studies and technology transfer KEYNOTE SPEAKERS * Holger Hermanns, Saarland University, Germany * Mike Hinchey, Lero-The Irish Software Engineering Research Centre, Ireland * Daniel Le Métayer - INRIA, France SPECIAL TRACK The conference programme will include a special track on "Modelling for Sustainable Development" with a separate Call for Papers that can be found at http://www.fing.edu.uy/inco/eventos/SEFM2011/CFP-MSD-special-track.txt. All queries on submissions to the special track should be sent to: sefm2011-msd(a)iist.unu.edu. The special track will have as keynote speaker: * Matteo Pedercini, Millennium Institute, USA LOCATION The conference will be held at the NH Columbia Hotel located close to the financial center of Montevideo and enjoying excellent views of the Plata river (Río de la Plata) - http://www.nh-hotels.com/nh/en/hotels/uruguay/montevideo/nh-columbia.html. SUBMISSION AND PUBLICATION Submissions to the conference must not have been published or be concurrently considered for publication elsewhere. All submissions will be peer-reviewed and judged on the basis of originality, contribution to the field, technical and presentation quality, and relevance to the conference. All papers must be written in English. Research and tool papers must not exceed 16 pages in the LNCS format while short papers must not exceed 8 pages in the LNCS format (see http://www.springer.de/comp/lncs/authors.html for details). All queries on the submissions should be sent to: sefm2011(a)fing.edu.uy. Papers must be submitted electronically via the Easychair System: http://www.easychair.org/conferences/?conf=sefm11 The proceedings will be published in the Springer Lecture Notes in Computer Science series (LNCS, http://www.springer.com/lncs) After the conference, authors of selected papers will be invited to submit an extended version of their work to be considered for publication in a special issue of the SoSyM journal (Software and Systems Modeling, Springer), following the standard reviewing process of the journal. COMMITTEES Conference Chair * Alberto Pardo, Universidad de la República, Uruguay Program Co-chairs * Gilles Barthe, IMDEA Software, Spain * Gerardo Schneider, Chalmers | Univ. of Gothenburg, Sweden Program Committee * Bernhard K. Aichering, Graz University of Technology, Austria * Luis Barbosa, University of Minho, Portugal * Gilles Barthe, IMDEA Software, Spain * Thomas Anung Basuki, Parahyangan Catholic University, Indonesia * Alexandre Bergel, University of Chile, Chile * Gustavo Betarte, Universidad de la República, Uruguay * Ana Cavalcanti, University of York, UK * Pedro R. D'Argenio, Univ. Nacional de Córdoba, Argentina * Van Hung Dang, Vietnam National University, Vietnam * George Eleftherakis, SEERC, Greece * José Luiz Fiadeiro, University of Leicester, UK * Martin Fränzle, Oldenburg University, Germany * Stefania Gnesi, ISTI-CNR, Italy * Rob Hierons, Brunel University, UK * Paola Inverardi, University of L'Aquila, UK * Jean-Marie Jacquet, University of Namur, Belgium * Tomasz Janowski, UNU-IIST, China * Jean-Marc Jezequel, IRISA, France * Joseph Kiniry, IT University of Copenhagen, Denmark * Paddy Krishnan, Bond University, Australia * Martin Leucker, TU Munich, Germany * Xuandong Li, Nanjing University, China * Peter Lindsay, The University of Queensland, Australia * Antónia Lopes, University of Lisbon, Portugal * Nenad Medvidovic, University of Southern California, USA * Mercedes Merayo, Universidad Complutense de Madrid, Spain * Stephan Merz, INRIA Nancy, France * Madhavan Mukund, Chennai Mathematical Institute, India * Cesar Muñoz, NASA, USA * Martín Musicante, UFRN, Brazil * Mizuhito Ogawa, JAIST, Japan * Olaf Owe, University of Oslo, Norway * Gordon Pace, University of Malta, Malta * Ernesto Pimentel, University of Málaga, Spain * Sanjiva Prasad, Indian Institute of Technology Delhi, India * Anders Ravn, Aalborg University, Denmark * Leila Ribeiro, UFRGS, Brazil * Augusto Sampaio, UFPE, Brazil * Gerardo Schneider, Chalmers | Univ. of Gothenburg, Sweden * Sebastian Uchitel, Imperial College London, UK, and UBA, Argentina * Willem Visser, University of Stellenbosch, South Africa * Sergio Yovine, CONICET and UBA, Argentina Organising Committee * Carlos Luna, Universidad de la República, Uruguay * Alberto Pardo, Universidad de la República, Uruguay * Luis Sierra, Universidad de la República, Uruguay Steering Committee * Manfred Broy, TU Munich, Germany * Antonio Cerone, UNU-IIST, Macao SAR, China * Mike Hinchey, Lero-The Irish Software Engineering Research Centre, Ireland * Mathai Joseph, TRDDC, Pune, India * Zhiming Liu, UNU-IIST, Macao SAR, China * Andrea Maggiolo-Schettini, Pisa University, Italy

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