October 2010 - Haskell

ANNOUNCE: iteratee-compress 0.1.1
by Maciej Piechotka 24 Oct '10

24 Oct '10

Iteratee-compress provides compressing and decompressing enumerators including flushing. Currently only gzip is provided but at least bzip is planned. Changes from previous version: - Independent from zlib library (Haskell one, not C) - Allow hand-flushing the contents (from outside). - Fix potential memory-leak Next goals: - BZip support - Generic interface for flushing To think about: - Should inner iteratee be able to request flushing? Regards PS. It did change API by removing dependency on zlib but I home such breakage in 0.1.x will be allowed

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Haskell Weekly News: Issue 155 - October 20, 2010 (Originally posted to Haskell-Cafe)
by Daniel Santa Cruz 24 Oct '10

24 Oct '10

Hello all, Malcolm Wallace noticed that I had not posted the HWN to this list, and requested that I do so. I realize that many of you are also following -Cafe, and I do apologize if this is a bit spamish due to that. Hopefully some of you will find this useful. -Daniel Welcome to issue 155 of the HWN, a newsletter covering developments in the [1]Haskell community in the week of October 10 - 16. This time around we again have 87 posts to HackageDB. Instead of posting the individual packages, we get to see and celebrate the 43 people behind these efforts. Want to keep a close eye on the haskellers that lurk twitter? Don Steward made [2]a twitter list of tweeting haskellers! Let him know if you'd like to be added to the list. There were a total of 24 new stories posted to the Haskell Reddit channel, 27 new questions taged with Haskell in StackOverflow, and 408 messages posted to Haskell-Cafe. So, what was hot last week? Announcements Gregory Crosswhite is pleased to [3]announce the release of a family of packages for type-level natural numbers. He also [4]announced tagged-list, a package which provides fixed-length lists that are tagged with a phantom type-level natural number corresponding to the length. Janis Voigtlander [5]announced that it is time to collect contributions for the 19th edition of the Haskell Communities & Activities Report. The submission deadline is November 1, 2010. Alexander Solla [6]announced his new "Facts" library. The Facts hierarchy is meant to contain commonly used, relatively static facts about the "real world." Kevin Jardine [7]announced polyToMonoid: a library that supplies two very general polyvariadic functions that can map their arguments into any monoid you specify. Simon Hengel [8]announced a new version of DocTest. DocTest now uses Haddock for parsing of comments. Interesting Threads on Haskell-Cafe Michael Snoyman [9]reported that Haskellers.com has become popular a lot falter that he anticipated. Read up on what changes are planned for Haskellers.com. Michael is very interested in some help with running the site. Jacek Generowicz [10]asked how to deal with dynamic dispatch on extensible sets of types. Uwe Schmidt [11]replied to a question about why HXT uses arrows as opposed to using monads. Good comments followed. Jason Dusek [12]asked if there is a way to write a Haskell data structure that is necessarily only one or two or seventeen items long; but that is nonetheless statically guaranteed to be of finite length? Twenty-three messages followed. Simon Thompson [13]annouced the availability of books for review for the Journal of Functonial Programming. Andrew Copping [14]summarized a report produced by Google Szwitzerland on taking a Python system and rewriting bits of it in Haskell, some of which is now in production use. Ben Franksen [15]ranted about the current "Haskell Blurb" on the first paragraph of haskell.org. Quite the read to end the week :) Top Reddit Stories * Using Haskell’s ‘newtype’ in C Domain: blog.nelhage.com Score: 37, Comments: 5 On Reddit: http://www.reddit.com/r/haskell/comments/dptzh/using_haskells_newtype_in_c/ Original: http://blog.nelhage.com/2010/10/using-haskells-newtype-in-c/ * The Haskell theme: consistent visual branding for Haskell Domain: haskell.org Score: 34, Comments: 11 On Reddit: http://www.reddit.com/r/haskell/comments/dqiej/the_haskell_theme_consistent… Original: http://www.haskell.org/pipermail/haskell-cafe/2010-October/084781.html * Haskellers: Survey results and new site features Domain: haskellers.com Score: 22, Comments: 6 On Reddit: http://www.reddit.com/r/haskell/comments/dr37b/haskellers_survey_results_an… Original: http://www.haskellers.com/news/1/ * My Experience Learning Haskell Domain: blog.virtucal.com Score: 21, Comments: 6 On Reddit: http://www.reddit.com/r/haskell/comments/drgcz/my_experience_learning_haske… Original: http://blog.virtucal.com/cyclical/2010/10/14/my-experience-learning-haskell… * Invertible monads for exception handling and memory allocations Domain: docs.yesodweb.com Score: 21, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/drkdj/invertible_monads_for_except… Original: http://docs.yesodweb.com/blog/invertible-monads-exceptions-allocations/ * Accelerating Haskell Array Codes with Multicore GPUs Domain: justtesting.org Score: 19, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/dq1yo/accelerating_haskell_array_c… Original: http://justtesting.org/accelerating-haskell-array-codes-with-multico * Unicode text performance improvements Domain: serpentine.com Score: 17, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/drinz/unicode_text_performance_imp… Original: http://www.serpentine.com/blog/2010/10/15/unicode-text-performance-improvem… * Like a coding challenge? Check out Code Quarterly! Domain: serpentine.com Score: 16, Comments: 9 On Reddit: http://www.reddit.com/r/haskell/comments/dpjgv/like_a_coding_challenge_chec… Original: http://www.serpentine.com/blog/2010/10/11/like-a-coding-challenge-check-out… * C9 Lecture: Ralf Lämmel on Monads Domain: channel9.msdn.com Score: 16, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/dq614/c9_lecture_ralf_lämmel_on_mo… Original: http://channel9.msdn.com/Shows/Going+Deep/C9-Lectures-Dr-Ralf-Lmmel-AFP-The… * Take the Haskellers.com survey Domain: spreadsheets.google.com Score: 15, Comments: 3 On Reddit: http://www.reddit.com/r/haskell/comments/dq7xj/take_the_haskellerscom_surve… Original: https://spreadsheets.google.com/viewform?formkey=dG8tcVhBdzRSS1lkdVV6U281em… Top StackOverflow Questions * When is memoization automatic in GHC Haskell? Question (votes: 14, answers: 3) http://stackoverflow.com/questions/3951012/when-is-memoization-automatic-in… * Why is my code using monadic lists from the List package so slow? Question (votes: 12, answers: 3) http://stackoverflow.com/questions/3916444/why-is-my-code-using-monadic-lis… * Haskell: lift vs liftIO Question (votes: 8, answers: 2) http://stackoverflow.com/questions/3921237/haskell-lift-vs-liftio * Can anyone suggest a good constraint library for Haskell? Question (votes: 8, answers: 2) http://stackoverflow.com/questions/3926656/can-anyone-suggest-a-good-constr… * Library function to compose a function with itself n times Question (votes: 6, answers: 4) http://stackoverflow.com/questions/3911060/library-function-to-compose-a-fu… * Evaluation of a small math type language that supports one variable Question (votes: 5, answers: 1) http://stackoverflow.com/questions/3906231/evaluation-of-a-small-math-type-… * What's the difference of a “class” in Haskell and in an “abstract class” in OO language? Question (votes: 5, answers: 4) http://stackoverflow.com/questions/3938779/whats-the-difference-of-a-class-… * Haskell and State Question (votes: 5, answers: 4) http://stackoverflow.com/questions/3944170/haskell-and-state * Can Haskell guard on abstract data types in a polymorphic function? Question (votes: 5, answers: 3) http://stackoverflow.com/questions/3944756/can-haskell-guard-on-abstract-da… Quotes of the Week * pumpkin: sounds like a lot of work! it's easier for me to just bitch about it * OlegKiselyov: Haskell is inconsistent in yet another way. * monochrom: just add #! /usr/bin/runghc to your haskell file. then type errors occur at runtime only. * IIcke: [haskell] is like wearing a corset, at the beginning is annoying, but then your tits look bigger and the world becomes a better place Contributors to HackageDB Who contributed, and how many uploads did they make? MichaelSnoyman (14), BryanOSullivan (11), GregoryCrosswhite (5), AndyStewart (5), GregoryCollins (4), JosePedroMagalhaes (3), StephenBlackheath (2), SjoerdVisscher (2), PaulTalaga (2), MichaelZuo (2), DanielDiaz (2), ConalElliott (2), AristidBreitkreuz (2), AlexanderSolla (2), YuriyIskra (1), VivianMcPhail (1), TristanSkudlik (1), TonyMorris (1), StephenTetley (1), SimonHengel (1), ReinierLamers (1), OlegBelozeorov (1), NeilMitchell (1), MaxBolingbroke (1), MatthiasBartsch (1), MatthewSottile (1), MasatakeDaimon (1), MarkSnyder (1), ManuelChakravarty (1), LeePike (1), KiYungAhn (1), KevinJardine (1), JustinBailey (1), IlyaPortnov (1), GeoffHulette (1), EugeneKirpichov (1), DonaldStewart (1), DanielSeidel (1), DanielSchoepe (1), CarlHowells (1), BenFranksen (1), ArieMiddelkoop (1), AlexSuraci (1) About the Haskell Weekly News New editions are posted to [16]the Haskell mailing list as well as to [17]the Haskell Sequence and [18]Planet Haskell. [19]RSS is also available, and headlines appear on [20]haskell.org. To help create new editions of this newsletter, please send stories to dstcruz * at * gmail * dot * 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://twitter.com/#!/donsbot/haskellers 3. http://groups.google.com/group/haskell-cafe/browse_thread/thread/c007154763… 4. http://groups.google.com/group/haskell-cafe/browse_thread/thread/ff95d6c78d… 5. http://groups.google.com/group/haskell-cafe/msg/d9d227b0f38bcf51 6. http://groups.google.com/group/haskell-cafe/browse_thread/thread/fc86bd03d0… 7. http://groups.google.com/group/haskell-cafe/browse_thread/thread/4ba5741441… 8. http://groups.google.com/group/haskell-cafe/browse_thread/thread/7982f0ad3b… 9. http://groups.google.com/group/haskell-cafe/browse_thread/thread/2440a1683f… 10. http://groups.google.com/group/haskell-cafe/browse_thread/thread/f0a05dd5b5… 11. http://groups.google.com/group/haskell-cafe/browse_thread/thread/38185e7ba6… 12. http://groups.google.com/group/haskell-cafe/browse_thread/thread/7ba4b3b038… 13. http://www.cs.kent.ac.uk/people/staff/sjt/JFP/available.html 14. http://groups.google.com/group/haskell-cafe/browse_thread/thread/81707fea2b… 15. http://groups.google.com/group/haskell-cafe/browse_thread/thread/a7c7b569dd… 16. http://www.haskell.org/mailman/listinfo/haskell 17. http://sequence.complete.org/ 18. http://planet.haskell.org/ 19. http://sequence.complete.org/node/feed 20. http://haskell.org/

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PostDoc and PhD Positions at Yale University
by Zhong Shao 22 Oct '10

22 Oct '10

[Apology for possible cross-postings!] The Department of Computer Science at Yale University is seeking applicants for PostDoc and PhD positions in the broad area of certified software. The successful applicants will be expected to participate in a rigorous research program on topics such as programming languages, formal semantics, certified operating systems, program verification, proof assistants and automation, concurrency and coordination, language-based security, and certifying compilers. The programming languages and operating systems group, led jointly by Professors Zhong Shao and Bryan Ford at Yale, is embarking on a multi-year effort to develop a new certified OS kernel that generalizes and unifies traditional OS abstractions in microkernels and hypervisors. The new effort advocates a modular certification framework for OS kernel components, which mirrors and enhances the modularity of the kernel itself. Using this framework, it aims to create not just a "one-off" lump of verified kernel code, but a statically and dynamically extensible kernel that can be incrementally built and extended with individual certified modules, each of which will provably preserve the kernel's overall safety and security properties. Important research questions include but are not limited to: what OS kernel structures can offer the best support for extensibility, security, and resilience? what program logics and semantic models can best capture these abstractions? what are the right programming languages and environments for developing such certified kernel? and how to build new automation facilities to make certified software really scale? Successful applicants should have a combination of creativity, self-motivation, and strong interests on applying programming language theory or formal methods to solve practical problems. Applicants for PostDoc positions must have a Ph.D. in Computer Science or a closely related field. The term of a PostDoc position is one year with an option to renew for up to four years. Starting date is negotiable (a preference will be given to those who can start by Spring 2011). Interested applicants for PostDoc positions should email a CV, research statement, and the names of three references with their email addresses and phone numbers to Zhong Shao (Email: zhong.shao at yale.edu) PhD positions (with full guaranteed financial support) are also available. Applicants interested in pursuing PhD studies can email either PI but should still submit their applications directly to the Yale Graduate School of Arts and Sciences (the deadline for Fall 2011 admission is January 2nd, 2011). More information regarding this research effort can be found in a white paper available at <http://flint.cs.yale.edu/ctos> or at the two PIs' research web sites <http://flint.cs.yale.edu> and <http://dedis.cs.yale.edu>. Inquiries can be directed to any PI. Professors Zhong Shao and Bryan Ford Department of Computer Science Yale University P.O. Box 208285 New Haven, CT 06520-8285, USA Phone: +1 (203) 432 6828 and +1 (203) 432 1055 Email: zhong.shao at yale.edu and bryan.ford at yale.edu

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ICFP 2011: Call for Workshop Proposals
by Wouter Swierstra 22 Oct '10

22 Oct '10

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2011 16th ACM SIGPLAN International Conference on Functional Programming September 19 - 21, 2011 Tokyo, Japan http://www.icfpconference.org/icfp2011 The 16th ACM SIGPLAN International Conference on Functional Programming will be held in Tokyo, Japan on September 19-21, 2011. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2011 and sponsored by SIGPLAN. These events should be more informal and focused than ICFP itself, include sessions that enable interaction among the attendees, and be fairly low-cost. The preference is for one-day events, but other schedules can also be considered. NEW THIS YEAR: The workshops are scheduled to occur on September 18 (the day before ICFP) and September 22-24 (the three days after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: November 19, 2010 Notification of acceptance: December 17, 2010 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2011 workshop co-chairs (Gabriele Keller and Derek Dreyer), via email to icfp11-workshops at mpi-sws.org by November 19, 2010. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by December 17, 2010, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2011/icfp11-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://acm.org/sigplan/sigplan_workshop_proposal.htm ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2010 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Gabriele Keller (University of New South Wales) Workshop Co-Chair: Derek Dreyer (MPI-SWS) General Co-Chair: Manuel Chakravarty (University of New South Wales) General Co-Chair: Zhenjiang Hu (National Institute of Informatics) Program Chair: Olivier Danvy (Aarhus University) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Gabriele Keller and Derek Dreyer), via email to icfp11-workshops at mpi-sws.org.

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Deepseq
by Gilmara Pompelli 22 Oct '10

22 Oct '10

Hello How do I use deepseq, this function to force evaluation, the way I did is correct? um :: IO () um = do conteudo <- learquivo "mkList1.txt" mapasort <- return (mapa psort conteudo) time $ mapasort `deepseq` return () Thanks

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Postdoc in Functional Programming at Chalmers
by John Hughes 19 Oct '10

19 Oct '10

The Functional Programming group at Chalmers is recruiting a postdoctoral researcher for a two year position, starting as soon as possible. The position is funded by a project in property-based testing with QuickCheck, with an emphasis specifically on language terms as test data. We're looking for someone with a PhD with a strong Functional Programming component. Experience with automated test case generation, whether with QuickCheck or other tools, and with formal specifications, is a merit. Full details (including how to apply) are on the web here: http://www.chalmers.se/cse/EN/news/vacancies/positions/post-doc-position-in… John Hughes

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Help-me read file
by Gilmara Pompelli 18 Oct '10

18 Oct '10

Hello I have a file with 100 lists, with 100 ints. I have to read the file and apply the map and sort functions on lists. II did it to read file: learquivo :: FilePath -> IO ([[Int]]) learquivo s = do conteudo <- readFile s return (read conteudo) But now applying the sort, the error appears: <interactive>:1:5: Couldn't match expected type `[a]' against inferred type `IO [[Int]]' how can I fix? Thanks

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New blog on Disciple/DDC development
by Ben Lippmeier 16 Oct '10

16 Oct '10

The blog is at: http://disciple-devel.blogspot.com/ more about the project here: http://trac.haskell.org/ddc/ Ben.

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ANNOUNCE: language-c-comments 0.1 package
by Geoff Hulette 08 Oct '10

08 Oct '10

Dear Haskell, Announcing the initial (0.1) release of the 'language-c-comments' package. If you need to grab the comments from a C source file, well now you can. Features: * Robust parsing of both single- and multi-line comments; * Handles obscure corner cases, e.g. http://hpaste.org/40456/a_valid_c_comment; * Comments include their position within the file, using the file position type from language-c for easy integration with that package; * Tested on the Linux kernel. Suggestions, feature requests, and bug reports welcome. Also, I may expand this package out into a full C preprocessor parser to complement language-c and enable source-to-source C translations that preserve the original formatting. If you have an opinion on what such a package should look like, I would be interested to hear about it. Cheers, -geoff

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ANNOUNCE: HaskellDB 2.0: Scrap your SQL strings
by Justin Bailey 08 Oct '10

08 Oct '10

What is it? ======== The HaskellDB library lets you generate SQL queries without writing any actual SQL. Unlike other query generating libraries, you choose the abstraction level. Queries can be built out of independent fragments, just like your programs. Leave hand-written, string-based, SQL libraries behind and check out HaskellDB. Where to get it? ============ You can get it from Hackage (http://hackage.haskell.org/package/haskelldb) or by using cabal (cabal install haskelldb). You also need drivers for your specific database. HaskellDB currently supports the HDBC family of drivers. First, download haskelldb-hdbc (http://hackage.haskell.org/package/haskelldb-hdbc) then get the appropriate package for your database: * ODBC: haskelldb-hdbc-odbc (http://hackage.haskell.org/package/haskelldb-hdbc-odbc) * Postgres: haskelldb-hdbc-postgresql (http://hackage.haskell.org/package/haskelldb-hdbc-postgresql) * Sqllite: haskelldb-hdbc-sqlite3 (http://hackage.haskell.org/package/haskelldb-hdbc-sqlite3) Documentation, Mailing List, Source, etc ======================= Go to http://trac.haskell.org/haskelldb for detailed information. What's New? ========= * New query capabilities: stored procedures, CASTs, query parameters, constants, and more. * Postgres SQL improvements. * Bug fixes around AND and OR associativity. * Query optimization improvements around aggregate expressions. * More tests. Details ===== Back in June 2009, Bjorn Bringert passed maintainership of HaskellDB to me. I've been working this summer to get a release out, which included: * Adding an examples/ directory to the source distribution. * Archiving and consolidating information to http://trac.haskell.org/haskelldb. * Accepting patches for various issues. I have used a lot of ORM & SQL-wrapper libraries during my career and HaskellDB is the first that I've found which does not require you to eventually break the abstraction. Learning to use the the library was a fun challenge but not one that many people are willing to take, when they can easily write SQL by hand. If the library was easier to get started with, I think it would be much more widely used. Help me get HaskellDB better documentation! If you are using HaskellDB and want to help: go to http://trac.haskell.org/haskelldb and write an article, write a blog post, get in touch with me, etc. When I saw that Rails 3.0 uses the "ARel" gem (based on the relational algebra) I groaned - Haskell has had that forever! We need to get the word out! Why 2.0? -------------- Last year Brian Bloniarz contributed an awesome patch which replaced HaskellDB's home-grown record system with the HList library by Oleg Kiselyov (and colleagues). I intended to work with the library for awhile and get a 1.0 release out. Unfortunately, HList proved too daunting for GHC and for me. Compile times went way up, and I could not isolate it enough to give GHC HQ a repro case. Even worse, HList required too many Oleg units for me to comprehend. I could usually fix compile errors, but found myself struggling to extend HaskellDB's functionality. In the end I felt I needed to back the patch out. I really hated to lose some of the functionality but in the end maintainability won out. At that point I had pushed a few patches with a v1.0 cabal file, so I thought it best to make this release 2.0. Who am I? --------------- I started using HaskellDB in early 2009. I use it more as a query-generating library than for executing SQL statements. I have written a largish system for generating a data-access layer in PHP from query descriptions in HaskellDB. Yes, I'm using Haskell to write PHP ... dirty! Unmaintained & Unrelated Packages ----------------------------------------------------- A couple of haskelldb related packages on Hackage are not maintained by me: * haskelldb-hdbc-mysql - This project was created and uploaded independent of me. Contact the author for specifics. However, the haskelldb-hdbc-odbc library is maintained by me and can be used to talk to MySQL. * HSQL (haskelldb-hsql, etc) - I cannot get this backend to compile on my platform. HSQL seems unmaintained so I have let the drivers decay. You'll notice I have not uploaded new packages or changed their version dependencies. * haskelldb-flat and haskelldb-dynamic - Both of these packages have suffered serious bitrot and are not maintained any longer.

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