April 2011 - Haskell - Haskell.org

ANNOUNCE: ioctl 0.0.1
by Maciej Piechotka 13 Sep '15

13 Sep '15

A package for type-safe I/O control. Currently only ioctl is supported. Currently simply a extract from my tuntap fork TODO: - Return the integer as well as structure (will break the API) - Port for Windows Network.Socket.IOCtl (as soon as I manage to setup some sane environment on this platform) - Wrapping around DeviceIoControl Example (in hsc): data NotRead = NotRead instance NotRead Int where ioctlReq _ = #const FIONREAD notRead s = ioctlsocket' s NotRead Regards

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ANNOUNCE: hspec-0.4.3 (color output and alternate mondaic api)
by Trystan Spangler 22 Jun '11

22 Jun '11

hspec version 0.4.3, Behavior Driven Development for Haskell, is now available! Improvements include red/yellow/green color output and writing output as the tests are running. Also, you can import Test.Hspec.Monadic rather than Test.Hspec if you want to use a WriterMonad based api. http://hackage.haskell.org/package/hspec https://github.com/trystan/hspec As always, any advice, comments, or questions are welcome, Trystan Spangler For those who would like to see an example, using the new alternate monadic api, running this program: > import Test.Hspec.Monadic > import Test.Hspec.HUnit > import Test.Hspec.QuickCheck (property) > import Test.HUnit (assertBool, assertEqual) > > main = hspec specs > > specs = describe "hspec 0.4.3" $ do > it "still allows a Bool expression to act as an example" > (replicate 5 1 == [1,1,1,1,1]) > > it "still allows HUnit assertions to act as examples" > (assertBool "lame example" True) > > it "still allows QuickCheck properties to act as examples" > (property $ \ i -> (i::Int) == i + 1 - 1) > > it "still shows a list of failed examples" > (undefined :: Bool) -- expected to fail > > it "still collects better data from failed HUnit examples" > (assertEqual "this should fail" 1 2) -- expected to fail > > it "still collects better data from failed QuickCheck examples" > (property $ \ i -> (i::Int) * 2 - 2 /= i) -- expected to fail > > it "now allows a monadic api" > (pending "I'm still not sure how to test this but this example is good evidence....") > > it "now outputs in color when writing to stdout" > (pending "I'm still not sure how to test this but trust me it works....") should send this to stdout in glorious red, yellow, and green: hspec 0.4.3 - still allows a Bool expression to act as an example - still allows HUnit assertions to act as examples - still allows QuickCheck properties to act as examples x still shows a list of failed examples FAILED [1] x still collects better data from failed HUnit examples FAILED [2] x still collects better data from failed QuickCheck examples FAILED [3] - now allows a monadic api # I'm still not sure how to test this but this example is good evidence.... - now outputs in color when writing to stdout # I'm still not sure how to test this but trust me it works.... 1) hspec 0.4.3 still shows a list of failed examples FAILED Prelude.undefined 2) hspec 0.4.3 still collects better data from failed HUnit examples FAILED this should fail expected: 1 but got: 2 3) hspec 0.4.3 still collects better data from failed QuickCheck examples FAILED *** Failed! Falsifiable (after 6 tests): 2 Finished in 0.0520 seconds 8 examples, 3 failures

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Possible Hackathon at MSR Cambridge this summer
by Simon Marlow 07 May '11

07 May '11

Hi Folks, We're looking into the possibility of holding a Haskell Hackathon at Microsoft Research, Cambridge, UK, this summer. The available dates are 22-24 July 12-14 August both Friday-Sunday. If you're interested in coming, use the following link to let us know which date you prefer: http://doodle.com/6iz8stzuinvduv27 please vote today or tomorrow (Tuesday), I'll close the poll on Wednesday. If you don't have a preference, there's no need to vote. Cheers, Simon

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2011 GTTSE/SLE Students' Workshop: Call for extended abstracts
by João Fernandes 30 Apr '11

30 Apr '11

* * * 2011 GTTSE/SLE Students' Workshop * * * July 5, 2011 Braga, Portugal http://gttse.wikidot.com/2011:students-workshop http://planet-sl.org/sle2011/ The co-location of SLE and GTTSE provides us the opportunity to combine their respective Doctoral Symposium and Participants' Workshop to form the GTTSE/SLE Students' Workshop. The students' workshop features presentations by the GTTSE and SLE participants: PhD students, PostDocs, practitioners, and other members of the computer science community. All registered participants are asked to submit an extended abstract in one of two forms: 1. Committed junior researchers may leverage the workshop as a means to present their relevant research and to receive feedback from senior researchers in the field. Submissions of this form should be an extended abstract of 2 pages in Springer LNCS style as a presentation proposal for the workshop. This may describe new ideas or early results, but there are no formal specifications as to the abstracts content. 2. In addition, doctoral students may use the workshop as a way to get feedback on their proposed doctoral research plan. Students should submit a 4 page (LNCS style, excluding references) abstract based on the following outline: - Problem Description and Motivation. - Brief Overview of Related Work, highlighting the gap the work aims to fill. - Proposed Solution, a high-level overview and any hypotheses that you have formulated. - Research Method, describing how you will validate or refute your hypotheses. It is understood that students at different stages of their research will be able to make more or less detailed and stabilized contributions to each of these sections. Therefore, we provide this outline as more of a guide than a strict requirement. Nonetheless, we encourage even early-stage PhD students to consider using this outline. Selection process for the SLE/GTTSE Students' Workshop The organizers will select proposals, with assistance as needed from the GTTSE scientific committee and the SLE program committee, for an interesting program. There are always more presentation proposals than there are slots in the workshop. There are likely to be 10-15 slots for presentations with 10-15 minutes each. The organizers will select a compelling set of presentation topics. This selection process is supposed to be informal and must not be confused with any sort of peer review or selective review. In particular, no formal feedback is returned to the authors of the 2 page abstracts. Authors are merely notified of the selection's outcome. Authors of 4 page doctoral research plans will receive informal feedback from reviewers chosen from the GTTSE scientific committee and SLE program committee. Authors who are not selected and who still wish to present some of their material may exhibit (and present) a poster at GTTSE. All reasonable submissions are distributed in printed form at the workshop. The abstracts will not be published online. The titles of selected presentations appear online though. Presenters may also voluntarily submit their slides for inclusion on the website. The GTTSE/SLE Students' Workshop will feature an award sponsored by SIG (The Software Improvement Group), to be given to the best presentation at the workshop. The awardee will be determined by a committee of senior attendees that is assembled by the organizers. Why present at and participate in the workshop? Each presenter benefits by means of the feedback from the renowned tutorial speakers and other participants. Presentation at the workshop may also spark off new collaborations. The school and conference, as a whole, also benefits from the workshop because the presentations constitute a blend of the current research interests in the GTTSE and SLE communities. Submission The submission deadline is May 27, 2011. This coincides with the end of Early Registration for both GTTSE and SLE. Abstracts must be submitted via EasyChair. See the event web pages (above) for submission details. Notes on the GTTSE post-proceedings After the school, all GTTSE participants (i.e., presenters, non-presenters, and non-submitters to the workshop) are encouraged to submit a contribution for inclusion into the post-proceedings. These contributions are properly reviewed and selection for the post-proceedings is competitive. Successful contributions have to meet high originality and quality standards. Compared to the usual peer-reviewed venue, GTTSE is particularly prepared to provide gentle and detailed feedback to PhD students. Submissions to the post-proceedings can have up to 15 pages. A designated call for contributions to the post-proceedings is distributed after the school. Event co-chair: Joost Visser, Software Improvement Group, The Netherlands Eric Van Wyk, University of Minnesota, United States

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ANNOUNCE: HFusion
by Facundo Domínguez 29 Apr '11

29 Apr '11

I'm pleased to announce the first release of HFusion[1] as a library. http://hackage.haskell.org/package/hfusion HFusion is a tool which transforms a subset of Haskell programs by applying fusion techniques based on hylomorphism, a program scheme by means of which it is possible to express a wide class of recursive functions. Hylomorphisms are automatically derived from user supplied definitions [1]. Related work includes [2,3,4,5]. The HFusion implementation allows to handle some interesting cases like: * primitive recursion * mutual recursion * recursion over multiple arguments * recursion based on regular functors The library is not particularly solid yet, but it may be of use to people interested in program transformations and certainly it would benefit from community feedback. Requests for fixes, explanations and improvements are more than welcome. ======= Use example ======= import HFusion.HFusion import Control.Monad.Trans(lift) import Language.Haskell.Parser(parseModule) fuseDefinitions :: String -> Either FusionError String fuseDefinitions sourceCode = runFusionState newVarGen$ -- Parse input with a Haskell parser. parseResult2FusionState (Language.Haskell.Parser.parseModule sourceCode) -- Convert the haskell AST to the AST used by HFusion. >>= hsModule2HsSyn -- Derive hylomorphisms for the definitions in the program. >>= lift . fmap snd . deriveHylos -- Fuse functions "zip" and "filter", which are expected -- to be defined in the sourceCode parameter, composing -- "filter" on the second argument of "zip" and naming "zf" -- the resulting recursive definition. >>= fuse "zip" 2 "filter" ["zf"] -- Translate the result from HFusion AST to Haskell source code. >>= return . hsSyn2HsSourceCode main = do cs <- readFile "examples.hs" putStr$ either (("There was an error: "++) . show) id$ fuseDefinitions cs --------- [1] http://www.fing.edu.uy/inco/proyectos/fusion [2] P. Johann and E. Visser. Warm fusion in Stratego: A case study in generation of program transformation systems. Annals of Mathematics and A.I., 29(1-4):1–34, 2000. [3] T. Yokoyama, Z. Hu, and M. Takeichi. Calculation rules for warming-up in fusion transformation. In Trends in Func. Programming, pages 399–41, 2005. [4] O. Chitil. Type-Inference Based Deforestation of Functional Programs. PhD thesis, RWTH Aachen, October 2000. [5] L. Németh. Catamorphism-Based Program Transformations for Non-Strict Functional Languages. PhD thesis, Glasgow University, 2000.

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ANNOUNCE: zeno-0.2
by Will Sonnex 28 Apr '11

28 Apr '11

I've recently finished an update to Zeno, a proof system for Haskell program properties. It now outputs programs and proofs as Isabelle/HOL theories and should hopefully be more usable in general. You still express properties to be proven within Haskell, but the syntax has changed. Here are some examples: reverse_twice xs = prove (reverse (reverse xs) :=: xs) elem_append xs ys y = givenBool (elem y ys) $ proveBool (elem y (xs ++ ys)) Lots more details on the wiki page: http://www.haskell.org/haskellwiki/Zeno, and you can try it online using TryZeno: http://www.doc.ic.ac.uk/~ws506/tryzeno. Cheers, Will

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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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