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ANNOUNCE: Haskell Communities and Activities Report (19th ed., November 2010)
by Janis Voigtländer 09 Nov '10

09 Nov '10

On behalf of all the contributors, I am pleased to announce that the Haskell Communities and Activities Report (19th edition, November 2010) is now available in PDF and HTML formats: http://haskell.org/communities/11-2010/report.pdf http://haskell.org/communities/11-2010/html/report.html Many thanks go to all the people that contributed to this report, both directly, by sending in descriptions, and indirectly, by doing all the interesting things that are reported. I hope you will find it as interesting a read as I did. If you have not encountered the Haskell Communities and Activities Reports before, you may like to know that the first of these reports was published in November 2001. Their goal is to improve the communication between the increasingly diverse groups, projects, and individuals working on, with, or inspired by Haskell. The idea behind these reports is simple: Every six months, a call goes out to all of you enjoying Haskell to contribute brief summaries of your own area of work. Many of you respond (eagerly, unprompted, and sometimes in time for the actual deadline ;-) to the call. The editor collects all the contributions into a single report and feeds that back to the community. When I try for the next update, six months from now, you might want to report on your own work, project, research area or group as well. So, please put the following into your diaries now: ---------------------------------------- End of April 2011: target deadline for contributions to the May 2011 edition of the HC&A Report ---------------------------------------- Unfortunately, many Haskellers working on interesting projects are so busy with their work that they seem to have lost the time to follow the Haskell related mailing lists and newsgroups, and have trouble even finding time to report on their work. If you are a member, user or friend of a project so burdened, please find someone willing to make time to report and ask them to "register" with the editor for a simple e-mail reminder in April (you could point me to them as well, and I can then politely ask if they want to contribute, but it might work better if you do the initial asking). Of course, they will still have to find the ten to fifteen minutes to draw up their report, but maybe we can increase our coverage of all that is going on in the community. Feel free to circulate this announcement further in order to reach people who might otherwise not see it. Enjoy! Janis Voigtlaender <hcar at haskell.org>

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CfP: JOURNAL OF APPLIED LOGIC, Special Issue on Automated Specification and Verification of Web Systems
by Temur Kutsia 08 Nov '10

08 Nov '10

[Apologies for multiple copies] ======================================================================== JOURNAL OF APPLIED LOGIC Special Issue on Automated Specification and Verification of Web Systems http://www.risc.uni-linz.ac.at/people/tkutsia/jal-wwv.html ======================================================================== SCOPE ----- This special issue of the Journal of Applied Logic is related to the topics of the workshop WWV'10: Automated Specification and Verification of Web Systems, which took place in Vienna on July 30-31, 2010. Both participants of the workshop and other authors are invited to submit contributions. The increased complexity of Web sites and the explosive growth of Web-based applications has turned their design and construction into a challenging problem. Nowadays, many companies have diverted their Web sites into interactive, completely-automated, Web-based applications (such as Amazon, on-line banking, or travel agencies) with a high complexity that requires appropriate specification and verification techniques and tools. Systematic, formal approaches to the analysis and verification can address the problems of this particular domain with automated and reliable tools that also incorporate semantic aspects. We solicit original papers on logic-based methods and techniques applied to Web sites, Web services or Web-based applications, such as: * Rule-based approaches to Web systems analysis, certification, specification, verification, and optimization * Algebraic methods for verification and certification of Web systems * Formal models for describing and reasoning about Web systems * Model-checking, synthesis and debugging of Web systems * Abstract interpretation and program transformation applied to the semantic Web * Intelligent tutoring and advisory systems for Web specifications authoring * Web quality and Web metrics * Web usability and accessibility * Testing and evaluation of Web systems and applications SUBMISSION ---------- We expect original articles (typically 15-25 pages; submission of larger papers will be evaluated depending on editorial constraints) that present high-quality contributions that have not been previously published and that must not be simultaneously submitted for publication elsewhere. Submissions must comply with JAL's author guidelines. They must be written in English and should be prepared using the Elsevier LaTeX package. Submissions are encouraged via the EasyChair submission system: http://www.easychair.org/conferences/?conf=jalwwv2010. IMPORTANT DATES --------------- * Submission of papers: March 7, 2011. * Notification: June 6, 2011. GUEST EDITORS -------------- * Laura Kov�cs (Vienna University of Technology) * Temur Kutsia (RISC, Johannes Kepler University Linz)

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Re: [Haskell] ANN: blaze-builder-0.2.0.0
by Simon Meier 08 Nov '10

08 Nov '10

Hi Antoine, Can the same technique be ported over to the binary package, or is it > somehow interface incompatible? > I'm not exactly sure what you mean by the same technique. If you mean using blaze-builder instead of Data.Binary.Builder as the Monoid that the Put writer monad in the Binary typeclass is using, then, yes, you can because Blaze.ByteString.Builder is a drop-in replacement for Data.Binary.Builder. However, in that case you loose some of the speedup of blaze-builder with respect to Data.Binary.Builder. The results https://gist.github.com/664979#file_comparison_to_binary_package.txt of the throughput benchmark (ported from the binary package) https://github.com/meiersi/blaze-builder/blob/master/benchmarks/BenchThroug… essentially show that you should not use the Put monad but the underlying Monoid directly for serialization. In my opinion, it is also not necessary to have a Writer monad (Put) by default. The only real benefit it brings is the nice do-notation. However, for the syntax we would rather go for a MonoidCatSyntax extension that introduces a 'cat' keyword analogously to the 'do' keyword. That's an extension which would also come in very handy for blaze-html and possibly other mappend-heavy applications. If you mean the Write abstraction, then its a partial yes. You can port it to binary, but I'm not sure how big the win is going to be. The current Data.Binary.Builder implementation suffers the problem that each builder needs to know the strategy for output construction and hence, the whole state of output construction. Passing all that data around makes its `mappend` implementation quite slow. I'd thought I'd heard rumbles a while back about a desire the change > the implementation of 'binary', but I don't know what happened to > that. I also heard some rumbles, but nothing concrete. Perhaps one of the 'binary' developers could comment on that issue? best regards, Simon

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ANN: blaze-builder-0.2.0.0
by Simon Meier 07 Nov '10

07 Nov '10

The blaze-builder library provides an abstraction of buffered output of byte streams and several convenience functions to exploit it. For example, it allows to efficiently serialize Haskell values to lazy bytestrings with a large average chunk size. The large average chunk size allows to make good use of cache prefetching in later processing steps (e.g. compression) and reduces the sytem call overhead when writing the resulting lazy bytestring to a file or sending it over the network. Note that blaze-builder was inspired by the Data.Binary.Builder module provided by the binary package. It was originally developed with the specific needs of the blaze-html package in mind. Since then it has been restructured to serve as a drop-in replacement for Data.Binary.Builder, which it *improves upon both in speed as well as expressivity.* See the following blog-post for more details: http://lambda-view.blogspot.com/2010/11/blaze-builder-library-faster.html best regards, Simon Meier

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ANNOUNCE: coroutine-enumerator
by Mario Blažević 05 Nov '10

05 Nov '10

The newly released coroutine-enumerator package can be used as a bridge between the enumerator and monad-coroutine packages. It provides two-way conversion functions between an Iteratee and an Await-suspending coroutine, and also between an Enumerator and a Yield-suspending coroutine. As a little example, the following program combines the http-enumerator, monad-coroutine, and SCC packages using the coroutine-enumerator package to print out all lines from the Hackage database containing substring "enumerator": > import Control.Exception.Base (SomeException) > import Control.Monad.Trans.Class (lift) > > import Data.ByteString (ByteString) > import Data.Text.Encoding (decodeUtf8) > > import Network.HTTP.Enumerator > > import Control.Monad.Coroutine > import Control.Monad.Coroutine.SuspensionFunctors > import Control.Monad.Coroutine.Nested > import Control.Monad.Coroutine.Enumerator > > import Control.Concurrent.SCC.Sequential > > main = httpRedirect (\_ _-> coroutineIteratee consumer) =<< parseUrl address > > address = "http://hackage.haskell.org/packages/archive/pkg-list.html" > > consumer :: Coroutine (Await [ByteString]) IO (Either SomeException ((), [ByteString])) > consumer = pipe translator (consume worker) >> return (Right ((), [])) > > translator :: Functor f => Sink IO (EitherFunctor (Await [a]) f) a -> Coroutine (EitherFunctor (Await [a]) f) IO () > translator sink = do chunks <- liftParent await > if null chunks > then lift (putStrLn "END") > else putList chunks sink >> translator sink > > worker :: Consumer IO ByteString () > worker = toChars >-> foreach (line `having` substring "enumerator") > (append (fromList "\n") >-> toStdOut) > suppress > > toChars :: Monad m => Transducer m ByteString Char > toChars = oneToOneTransducer decodeUtf8 >-> coerce Alternatively, the worker coroutine can parse the XML database and print out all elements whose any attribute value contains the substring "enumerator": > worker = toChars > >-> parseXMLTokens > >-> foreach (xmlElementHavingTagWith (xmlAttributeValue `having` substring "enumerator") > `nestedIn` xmlElementContent) > (coerce >-> toStdOut) > suppress

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ANNOUNCE: version 0.6 of monad-coroutine and SCC
by Mario Blažević 05 Nov '10

05 Nov '10

Packages monad-coroutine and SCC have been upgraded to version 0.6 on Hackage. The monad-coroutine package exports a generic monad transformer Coroutine: Functor s => MonadTrans (Coroutine s). A Coroutine-transformed monad can suspend at any point, returning its resumption wrapped in the functor s. There are also some functions for manipulating and running coroutines, as well as a couple of useful suspension functors such as Yield and Await. Version 0.6 of monad-coroutine makes running pairs of coroutines simpler by adding several predefined resolvers. The new version of Streaming Component Combinators (a.k.a. SCC) is mostly about performance enhancements. The coroutines now communicate through chunks of data rather than individual items, which reduces the coroutine switching overhead. The module hierarchy has been reorganized for easier use, but the exported type and function names have mostly remained the same. Both packages have been tested with GHC 6.12.3 and 7.0.

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Haskell Weekly News: Issue 157 - November 03, 2010
by Daniel Santa Cruz 03 Nov '10

03 Nov '10

Welcome to issue 157 of the HWN, a newsletter covering developments in the [1]Haskell community in the week of October 24 - 30. Seems that things quieted down a bit this week. We saw 85 new or updated packages in Hackage, 29 (-5) stories posted to Reddit, 25 (-22) questions posted to StackOverflow, and 302 (-20) messages posted on the -cafe mailing list. Maybe some of the effects of ICFP have died down a bit? Don Stewart posted some interesting numbers comparing different programming communities in Reddit. As we can see, we seem to be very well represented: /r/python 16.3k users /r/javascript 8k users /r/ruby 6k users /r/php 5.7k users /r/haskell 5.5k users /r/cpp 5.3k users /r/lisp 3.9k users /r/perl 3.5k users /r/java/ 3k users /r/erlang 1.8k users /r/c_programming 1.7k users /r/scheme 1.2k users /r/clojure 1.2k users /r/asm 1.1k users /r/scala 1k users We hope to see pictures, videos, and blog posts from the people that are attending BelHac this weekend! So, what was hot last week? Announcements Anton Kholomiov [2]announced his new csound-expression combinator libary. It features liberation from id-style csound code, haskore-like composition structures, type-safe composable opcodes and simple instrument interface. Maciej Piechotka [3]announced a new version of iteratee-compress, which provides compressing and decompressing enumerators including flushing. Currently only gzip is available, but bzip is planned. Tim Docker [4]announced an update to his Chart (v0.14) library. This is a library for drawing 2D data plots. Eugene Kirpichov [5]announced an update to his timeplot library. This library is a tool for visualizing time series from log files. He also provided us with some [6]pretty pictures. Niklas Broberg couldn't find a library to manipulate Java source code, so he [7]announced the creation of language-java. One of the [8]bigger updates last week was brought to us by the darcs team. It contains many improvements over the 2.4 series. Most notable are the performance improvements in record and pull, and the --bisect option for trackdown. Way to go guys! John Lato [9]announced the initial release of mutable-iter, an extension to the iteratee package which uses mutable buffers. Top Reddit Stories * Neat Haskell commenting trick Domain: self.haskell Score: 77, Comments: 6 On Reddit: http://www.reddit.com/r/haskell/comments/dyvsi/neat_haskell_commenting_tric… Original: /r/haskell/comments/dyvsi/neat_haskell_commenting_trick/ * Haskell Halloween! Domain: i.imgur.com Score: 53, Comments: 5 On Reddit: http://www.reddit.com/r/haskell/comments/dyznc/haskell_halloween/ Original: http://i.imgur.com/t7qWf.jpg * OCaml for Haskellers (Inside 245s) Domain: blog.ezyang.com Score: 41, Comments: 27 On Reddit: http://www.reddit.com/r/haskell/comments/dw2cy/ocaml_for_haskellers_inside_… Original: http://blog.ezyang.com/2010/10/ocaml-for-haskellers/ * MTL 2.0 has been uploaded good bye old mtl, hello monads-fd! Domain: hackage.haskell.org Score: 40, Comments: 11 On Reddit: http://www.reddit.com/r/haskell/comments/dx8ml/mtl_20_has_been_uploaded_goo… Original: http://hackage.haskell.org/package/mtl-2.0.0.0 * Linear vs. compositional type checking Domain: gergo.erdi.hu Score: 34, Comments: 10 On Reddit: http://www.reddit.com/r/haskell/comments/dwip1/linear_vs_compositional_type… Original: http://gergo.erdi.hu/blog/2010-10-23-the_case_for_compositional_type_checki… * Tour of a real toy Haskell program Domain: mainisusuallyafunction.blogspot.com Score: 29, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/dwjvo/tour_of_a_real_toy_haskell_p… Original: http://mainisusuallyafunction.blogspot.com/2010/10/tour-of-real-toy-haskell… * Ride the snake: Calling Python libraries from Haskell Domain: john-millikin.com Score: 26, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/dxj0e/ride_the_snake_calling_pytho… Original: http://john-millikin.com/articles/ride-the-snake/ * Announcing: Snap Framework v0.2.15 Domain: snapframework.com Score: 25, Comments: 3 On Reddit: http://www.reddit.com/r/haskell/comments/dy94z/announcing_snap_framework_v0… Original: http://snapframework.com/blog/2010/10/27/snap-0.2.15-released * Yesod 0.6.0 Released Domain: docs.yesodweb.com Score: 23, Comments: 8 On Reddit: http://www.reddit.com/r/haskell/comments/dwn5v/yesod_060_released/ Original: http://docs.yesodweb.com/blog/yesod-0-6/ * darcs 2.5 released Domain: wiki.darcs.net Score: 21, Comments: 3 On Reddit: http://www.reddit.com/r/haskell/comments/dyo7d/darcs_25_released/ Original: http://wiki.darcs.net/Releases/2.5 Top StackOverflow Questions * type constructor or class error Question (votes: 0, answers: 4): Read on SO: http://stackoverflow.com/questions/4060486/type-constructor-or-class-error * parse error in else Question (votes: 0, answers: 1): Read on SO: http://stackoverflow.com/questions/4053638/parse-error-in-else * xmonad could not find module `XMonad': broken package Question (votes: 0, answers: 1): Read on SO: http://stackoverflow.com/questions/4037101/xmonad-could-not-find-module-xmo… * Haskell: I/O and Returning From a Function Question (votes: 1, answers: 3): Read on SO: http://stackoverflow.com/questions/4056867/haskell-i-o-and-returning-from-a… * Collapse arrow to list Question (votes: 1, answers: 1): Read on SO: http://stackoverflow.com/questions/4030439/collapse-arrow-to-list * how to force the evaluation of this expression? Question (votes: 1, answers: 1): Read on SO: http://stackoverflow.com/questions/4027097/how-to-force-the-evaluation-of-t… * How to get type parameters from SYBs dataTypeOf Question (votes: 1, answers: 1): Read on SO: http://stackoverflow.com/questions/4007693/how-to-get-type-parameters-from-… * How to sort the list by its accountID using quick sort in Haskell. Question (votes: 1, answers: 2): Read on SO: http://stackoverflow.com/questions/4006811/how-to-sort-the-list-by-its-acco… * Parsec parse many question Question (votes: 2, answers: 2): Read on SO: http://stackoverflow.com/questions/4058765/parsec-parse-many-question * Type error using Criterion Question (votes: 2, answers: 2): Read on SO: http://stackoverflow.com/questions/4033103/type-error-using-criterion HackageDB Updates Who contributed, and what got uploaded? * AdamVogt: xmonad-extras * AlexSuraci: atomo * AndreasVoellmy: nettle-openflow * AndrewCoppin: AC-EasyRaster-GTK, AC-Terminal * BenLippmeier: buildbox, buildbox-tools * BryanOSullivan: text-icu * ChrisDone: throttle * ChrisKuklewicz: hprotoc, protocol-buffers-descriptor * ChristiaanBaaij: clash * ClaudeHeilandAllen: gmndl * DanDoel: bytestring-show * DanielDiaz: DTC * DougBeardsley: heist * ErikHesselink: flock * EugeneKirpichov: timeplot * GaneshSittampalam: HTTP * GregoryCollins: snap-core, snap-server * GregoryWeber: sifflet, sifflet-lib * GrzegorzChrupala: morfette * HeinrichApfelmus: operational * IlyaPortnov: todos * JacobStanley: network-info * JanRochel: SoccerFun * JasperVanDerJeugt: hakyll * JeremyShaw: web-routes-happstack * JinjingWang: practice-room * JohanTibell: network * JohnGoerzen: twidge * JohnLato: ListLike, hCsound, iteratee, iteratee-mtl, mutable-iter, sndfile-enumerators * JohnMacFarlane: texmath * JohnMillikin: cpython, expat-enumerator, libxml-enumerator, libxml-sax, ncurses, yajl-enumerator * JudeNagurney: augeas * KetilMalde: bio, dephd, flower * KiYungAhn: yices * MaciejPiechotka: iteratee-compress * MarcosViera: AspectAG * MattBrown: MissingPy * MaxBolingbroke: ansi-terminal * MichaelIlseman: yaml-light * MichaelSnoyman: authenticate, hamlet, neither, persistent, persistent-postgresql, persistent-sqlite, wai, yesod, yesod-auth, yesod-examples * MichelBoucey: ip6addr * NiklasBroberg: language-java * PetrRockai: shellish * ReinierLamers: darcs * RichardSmith: linux-ptrace, posix-waitpid * RossPaterson: mtl * SebastianFischer: weighted-regexp * SinisaBidin: websockets * ThomasDuBuisson: crypto-api, hsXenCtrl, pureMD5 * ThomasSchilling: murmur-hash * TimDocker: Chart * TomHawkins: improve * TonyMorris: JSON-Combinator * VincentHanquez: cryptohash * YoshikuniJujo: mtlparse, regexpr About the Haskell Weekly News New editions are posted to [10]the Haskell mailing list as well as to [11]the Haskell Sequence and [12]Planet Haskell. [13]RSS is also available, and headlines appear on [14]haskell.org. To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. The code used to produce this version of the newsletter is not yet publicly available, as it is a complete hack designed to get things started again. Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://hackage.haskell.org/package/csound-expression 3. http://groups.google.com/group/haskell-cafe/browse_thread/thread/faf1da04ba… 4. http://groups.google.com/group/haskell-cafe/browse_thread/thread/0759530428… 5. http://groups.google.com/group/haskell-cafe/browse_thread/thread/4215122a77… 6. http://www.haskell.org/haskellwiki/Timeplot 7. http://groups.google.com/group/haskell-cafe/browse_thread/thread/4c9b3e1499… 8. http://groups.google.com/group/haskell-cafe/browse_thread/thread/229c751ebc… 9. http://article.gmane.org/gmane.comp.lang.haskell.general/18274 10. http://www.haskell.org/mailman/listinfo/haskell 11. http://sequence.complete.org/ 12. http://planet.haskell.org/ 13. http://sequence.complete.org/node/feed 14. http://haskell.org/

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[Haskell] ANNOUNCE: Sifflet visual programming language, release 1.2
by gdweber＠iue.edu 31 Oct '10

31 Oct '10

Sifflet and sifflet-lib 1.2 are now available on Hackage. Sifflet is a visual, functional programming language and support system for students learning about recursion. Sifflet programmers define functions by drawing diagrams, and the Sifflet interpreter uses diagrams to show how the function calls are evaluated. Sifflet-lib is the library containing many modules of the sifflet application. What's New ---------- - Compatible with and requires HXT version 9.0 - Sifflet(-lib) requires only the core of HXT. Due to the split of HXT into several packages, sifflet no longer indirectly requires curl. This should make it easier to install on Windows! However, I haven't been able to test installing it on Windows myself. Reports are welcome! About Sifflet ------------- Sifflet is a visual, functional programming language intended as an aid for learning about recursion. * A picture explains Sifflet better than words: please see the screenshot showing how to evaluate 3!: http://mypage.iu.edu/~gdweber/software/sifflet/home.html * Features: - Visual editor. - Visual tracer/debugger which shows how recursive and other function calls are evaluated. To support active learning and avoid screen clutter, Sifflet displays only as much of the computation as the user requests. - A carefully crafted tutorial with 31 pictures and about as many pages. - Number, string, and list data types. - A small collection of primitive functions. - Runnable examples of compound functions. - Sifflet functions can be "exported" to Scheme, Python 3, and Haskell. * Download: http://hackage.haskell.org/package/sifflet-lib http://hackage.haskell.org/package/sifflet * Home page: http://mypage.iu.edu/~gdweber/software/sifflet/home.html * Tutorial: http://mypage.iu.edu/~gdweber/software/sifflet/doc/tutorial.html -- ___ ___ __ _ / _ \ / _ \| | | | Gregory D. Weber, Associate Professor / /_\// / | | | /\ | | Indiana University East / /_\\/ /__| | |/ \| | http://mypage.iu.edu/~gdweber/ \____/\_____/\___/\__/ Tel. (765) 973-8420; FAX (765) 973-8550

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Specification and prover for Haskell
by Romain Demeyer 31 Oct '10

31 Oct '10

Hello, I'm working on static verification in Haskell, and I search for existing works on specification of Haskell programs (such as pre/post conditions, for example) or any other functional language. It would be great if there exists a prover based on this kind of specifications. I already found the ESC/Haskell. Do you know some other works which could be interesting? Thanks, rde.

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ANNOUNCE zeno 0.1.0
by Will Sonnex 31 Oct '10

31 Oct '10

Hi all, My masters project Zeno was recently mentioned on this mailing list so I thought I'd announce that I've just finished a major update to it, bringing it slightly closer to being something useful. Zeno is a fully automated inductive theorem proving tool for Haskell programs. You can express a property such as "takeWhile p xs ++ dropWhile p xs === xs" and it will prove it to be true for all values of p :: a -> Bool and xs :: [a], over all types a, using only the function definitions. Now that it's updated it can use polymorphic types/functions, and you express properties in Haskell itself (thanks to SPJ for the suggestion). It still can't use all of Haskell's syntax: you can't have internal functions (let/where can only assign values), and you can't use type-classed polymorphic variables in function definitions - you'll have to create a monomorphic instance of the function -but I hope to have these added reasonably soon. It's also still missing primitive-types/IO/imports so it still can't be used with any real-world Haskell code, it's more a bit of theorem proving "fun". You can try it out at http://www.doc.ic.ac.uk/~ws506/tryzeno, the code file given there has some provable properties about a few prelude functions among other things. Another feature is that it lists all the sub-properties it has proven within each proof. When it verifies insertion-sort "sorted (insertsort xs) === True" it also proves the antisymmetry of "<=" and that the "insert" function preserves the "sorted" property. Any suggestions or feedback would be greatly appreciated. Cheers, Will

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