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Crazy class stuff
by Taral 13 Mar '07

13 Mar '07

I tried this: class MonadTrans' i o where lift' :: i a -> o a instance (MonadTrans t, Monad m) => MonadTrans' m (t m) where lift' = lift instance (MonadTrans' a b, MonadTrans' b c) => MonadTrans' a c where lift' = lift' . lift' And it doesn't work. I know what I want it to do, how do I express it right? -- Taral <taralx(a)gmail.com> "You can't prove anything." -- Gödel's Incompetence Theorem

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Commercial Users of Functional Programming: call for speaker nominations
by Simon Peyton-Jones 13 Mar '07

13 Mar '07

Commercial Users of Functional Programming (CUFP) 2007 Oct 4 2007, Freiburg, Germany === Call for speaker nominations and talk proposals === Functional languages have been under academic development for over 25 years, and remain fertile ground for programming language research. Recently, however, developers in industrial, government, and open source projects have begun to use functional languages very successfully in practical applications. In these settings, functional programming has often provided dramatic leverage, including whole new ways of thinking about the original problem. The goal of the CUFP workshop is to act as a voice for these users of functional languages. The workshop supports the increasing viability of functional programming in the commercial, governmental, and open-source space by providing a forum for FP professionals to share their experiences and ideas, whether those ideas are related to business, management, or engineering. The workshop is also designed to enable the formation and reinforcement of relationships that further the commercial use of functional languages. Speaking at CUFP If you use functional programming as a means, rather than as an end, this message is an invitation for you to offer to give a talk at the workshop. Alternatively, you may know someone else who would give a good talk: please nominate them. Talks are typically about 30-45 minutes long, but can be shorter. They aim to inform participants about how functional programming played out in real-world applications, focusing especially on the re-usable lessons learned, or insights gained. Your talk does not need to be highly technical; for this audience, reflections on the commercial, management, or software engineering aspects are, if anything, more important. You do not need to submit a paper! If you are interested in offering a talk, or nominating someone to do so, send an e-mail to kfisher at research.att.com or simonpj at microsoft.com by June 1, 2007 with a short description of what you'd like to talk about or what you think your nominee should give a talk about. Such descriptions should be roughly a page in length.

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Haskell Weekly News: March 12, 2007
by dons＠cse.unsw.edu.au 12 Mar '07

12 Mar '07

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20070312 Issue 59 - March 12, 2007 --------------------------------------------------------------------------- Welcome to issue 59 of HWN, a weekly newsletter covering developments in the [1]Haskell community. This week we see the 2007 Haskell Workshop announcement, Haskell.org's participation in the Google Summer of Code gets underway, and of course, new libraries! 1. http://haskell.org/ Announcements Google Summer of Code and Haskell.org. Malcolm Wallace [2]announced that Haskell.org has once again applied to be a mentoring organisation for the Google Summer of Code. If you are a student who would like to earn money hacking in Haskell, or you are a non-student who has a cool idea for a coding project but no time to do it yourself, then visit the [3]SoC wiki to gather ideas, and add yourself to the list of interested people! Add new ideas for projects! 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/20232 3. http://hackage.haskell.org/trac/summer-of-code Haskell Workshop Call for Papers. Gabriele Keller [4]announced the initial call for papers for the Haskell Workshop 2007, part of the 2007 International Conference on Functional Programming (ICFP). The purpose of the Haskell Workshop is to discuss experience with Haskell, and possible future developments for the language. The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of Haskell. 4. http://article.gmane.org/gmane.comp.lang.haskell.general/14977 Data.CompactString 0.3: Unicode ByteString. Twan van Laarhoven [5]announced version 0.3 of the Data.CompactString library. Data.CompactString is a wrapper around Data.ByteString supporting Unicode strings. 5. http://article.gmane.org/gmane.comp.lang.haskell.general/14973 harchive-0.2: backup and restore software in Haskell. David Brown [6]announced release 0.2 of [7]harchive, a program for backing up and restoring data. The package is available [8]from Hackage. 6. http://article.gmane.org/gmane.comp.lang.haskell.general/14972 7. http://www.davidb.org/darcs/harchive/ 8. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/harchive-0.2 New release of regex packages. Chris Kuklewicz [9]announced new versions of the regex-* packages (base,compat,dfa,parsec,pcre,posix,tdfa,tre). There is a new [10]wiki page with documentation relating to these packages. All packages are available from [11]Hackage, under the [12]Text Category. 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/20189 10. http://haskell.org/haskellwiki/Regular_expressions 11. http://hackage.haskell.org/packages/hackage.html 12. http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Text StaticDTD: type safe markup combinators from DTDs. Marcel Manthe [13]announced a tool that transforms a Document Type Definition to a library. The resulting library contains combinators that assure proper nesting of elements. The plan is to add more constraints that will also take care of the order of occurrence of children. The parsing of the DTD is done with HaXml. The code is [14]available via darcs. 13. http://article.gmane.org/gmane.comp.lang.haskell.cafe/20218 14. http://m13s07.vlinux.de/darcs/StaticDTD/ IPv6 support for network package. Bryan O'Sullivan [15]announced that he'd added IPv6 support to the network package. 15. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6363 Type-level binary arithmetic library. Oleg Kiselyov and Chung-chieh Shan [16]announced a [17]new library for arbitrary precision binary arithmetic over natural kinds. The library supports addition/subtraction, predecessor/successor, multiplication/division, exp2, full comparisons, GCD, and the maximum. At the core of the library are multi-mode ternary relations Add and Mul where any two arguments determine the third. Such relations are especially suitable for specifying static arithmetic constraints on computations. The type-level numerals have no run-time representation; correspondingly, all arithmetic operations are done at compile time and have no effect on run-time. 16. http://article.gmane.org/gmane.comp.lang.haskell.general/14961 17. http://pobox.com/~oleg/ftp/Computation/resource-aware-prog/BinaryNumber.hs Haskell' This section covers the [18]Haskell' standardisation process. * [19]Deriving Functor 18. http://hackage.haskell.org/trac/haskell-prime 19. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2135 Libraries This week's proposals and extensions to the [20]standard libraries. * [21]Add IPv6 support to network library * [22]Error handling conventions 20. http://haskell.org/haskellwiki/Library_submissions 21. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6377 22. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6382 Discussion Avoiding intermediate data structures. David Roundy [23]opened discussion on techniques for avoiding intermediate data structures in Haskell code 23. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/20319 Maybe a different Maybe. Joachim Breitner [24]wondered about avoiding intermediate Maybe constructs 24. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/20300 Blog noise [25]Haskell news from the blogosphere. * [26]STM, IO, and a Simple Persistence Model * [27]Dynamic programming in Haskell * [28]Collected 'good math/bad math' Haskell articles * [29]3 open questions about monads * [30]Documentation, libraries and speed matter * [31]Why monads matter * [32]Design Patterns in Haskell: bracket * [33]Practical Haskell: shell scripting with error handling and privilege separation * [34]Simple socket programming * [35]'interact' for TCP sockets * [36]Monads in C, part 3 * [37]Directory tree printing in Haskell. Part 2 * [38]Monads through Pictures * [39]Notes on hacking Haskell * [40]Wanted: Haskell Programmer * [41]Why Publish CS Papers Without Code? * [42]The 8 ways to report errors in Haskell 25. http://planet.haskell.org/ 26. http://mult.ifario.us/articles/2007/03/04/stm-and-io 27. http://sequence.complete.org/node/263 28. http://scienceblogs.com/goodmath/goodmath/programming/haskell/ 29. http://www.randomhacks.net/articles/2007/03/05/three-things-i-dont-understa… 30. http://kawagner.blogspot.com/2007/03/why-do-most-people-seem-to-use-inferio… 31. http://www.rfc1149.net/blog/2007/03/06/why-monads-matter/ 32. http://notes-on-haskell.blogspot.com/2007/03/design-patterns-in-haskell-bra… 33. http://cgi.cse.unsw.edu.au/~dons/blog/2007/03/06#programmable-semicolons 34. http://metavar.blogspot.com/2007/03/simple-socket-programming.html 35. http://stephan.walter.name/blog/computers/programming/haskell/interacttcp.h… 36. http://sigfpe.blogspot.com/2007/03/monads-in-c-pt-iii.html 37. http://blog.moertel.com/articles/2007/03/07/directory-tree-printing-in-hask… 38. http://www.bolour.com/papers/monads-through-pictures.html 39. http://metavar.blogspot.com/2007/03/haskell-hacking-notes-or-prelude-to.html 40. http://blogs.teamb.com/craigstuntz/archive/2007/03/09/WantedHaskellDevelope… 41. http://billmill.org/why_no_code 42. http://www.randomhacks.net/articles/2007/03/10/haskell-8-ways-to-report-err… Quotes of the Week * fishkandy: The problem with comparing apples to apples is that haskell has 'mango daiquiri' as a basic fruit * fax--: I wake up with a headache because of you, Haskell * norpan: I use functions, but i don't use them as arrows: I prefer silver bullets * ray: Some people claim everything is lisp. One time I was eating some spaghetti and someone came by and said: 'Hey, nice lisp dialect you're hacking in there' * roconnor: Damn it! Haskell pseudo code is indistinguishable from actual code * shapr: Today's nifty error message: *Main> thread blotttchhhkrrreeeedaaa dddinbbbdllleooofcccikkkneeeidddt eiiilnnnydddeeefffiiinnniiittteeelllyyy * stepcut: C? isn't that some low-level language that compilers output to? * wkh: Why does the haskell webpage link to 'research papers' under the 'getting started' section? Code Watch Tue Mar 6 06:31:12 PST 2007. Simon Marlow. [43]add noDuplicate#. This primop ensures that the current computation is not being duplicated, by calling threadPaused(). The idea is to use it inside unsafePerformIO/unsafeInterleaveIO (see #986). 43. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/19536 About the Haskell Weekly News Each week, new editions are posted to [44]the Haskell mailing list as well as to [45]the Haskell Sequence and [46]Planet Haskell. [47]RSS is also available, and headlines appear on [48]haskell.org. Headlines are available as [49]PDF. To help create new editions of this newsletter, please see the [50]contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get [51]http://www.cse.unsw.edu.au/~dons/code/hwn 44. http://www.haskell.org/mailman/listinfo/haskell 45. http://sequence.complete.org/ 46. http://planet.haskell.org/ 47. http://sequence.complete.org/node/feed 48. http://haskell.org/ 49. http://www.cse.unsw.edu.au/~dons/code/hwn/archives/20070312.pdf 50. http://haskell.org/haskellwiki/HWN 51. http://www.cse.unsw.edu.au/~dons/code/hwn

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Re: [Haskell] Transformation of boolean formulas
by Dominik Luecke 12 Mar '07

12 Mar '07

Sorry for the copy and paste error... Neil Mitchell schrieb: > Hi Dominik > >> although I have subscribed to the Haskell mailing list, my messages are >> automatically rejected when I try to send a mail to Haskell > > Not anymore! > > And btw, if you want to discuss transformation of boolean formulas, > rather than announce a package that does them, haskell-cafe is > probably a better choice. > > Thanks > > Neil -- Dominik Luecke Phone +49-421-218-64265 Dept. of Computer Science Fax +49-421-218-9864265 University of Bremen luecke(a)tzi.de P.O.Box 330440, D-28334 Bremen PGP-Key ID 0x2D82571B

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Transformation of boolean formulas
by Dominik Luecke 12 Mar '07

12 Mar '07

Hello, although I have subscribed to the Haskell mailing list, my messages are automatically rejected when I try to send a mail to Haskell Regards, Dominik -- Dominik Luecke Phone +49-421-218-64265 Dept. of Computer Science Fax +49-421-218-9864265 University of Bremen luecke(a)tzi.de P.O.Box 330440, D-28334 Bremen PGP-Key ID 0x2D82571B

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Haskell Workshop Call for Papers
by Gabriele Keller 11 Mar '07

11 Mar '07

My apologies if you receive multiple copies of this: ------------------------------------------------------------------------- ACM SIGPLAN 2007 Haskell Workshop Call for Papers Freiburg, Germany 30 September, 2007 The Haskell Workshop 2007 will be part of the 2007 International Conference on Functional Programming (ICFP) as an associated, ACM SIGPLAN sponsored workshop. Previous Haskell Workshops have been held in La Jolla (1995), Amsterdam (1997), Paris (1999), Montreal (2000), Firenze (2001), Pittsburgh (2002), Uppsala (2003), Snowbird (2004), Tallinn (2005), and Portland, Oregon (2006) Topics The purpose of the Haskell Workshop is to discuss experience with Haskell, and possible future developments for the language. The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of Haskell. Topics of interest include, but are not limited to, the following: * Language Design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, in the form of a formal treatment of the semantics of the present language or future extensions, type systems, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management as well as foreign function and component interfaces; * Tools, in the form of profilers, tracers, debuggers, pre-processors, and so forth; * Applications, Practice, and Experience with Haskell for scientific and symbolic computing, database, multimedia and Web applications, and so forth as well as general experience with Haskell in education and industry; * Functional Pearls being elegant, instructive examples of using Haskell. Papers in the latter two categories need not necessarily report original research results; they may instead, for example, report practical experience that will be useful to others, re-usable programming idioms, or elegant new ways of approaching a problem. The key criterion for such a paper is that it makes a contribution from which other practitioners can benefit. It is not enough simply to describe a program! Submission details Submission Deadline: Friday, June 15th 2007 Author Notification: Monday, July 16th 2007 Final Submission: Friday, August 3rd 2007 Submitted papers should be in postscript or portable document format, formatted using the ACM SIGPLAN style guidelines (http://www.acm.org/sigs/sigplan/authorInformation.htm) The length is restricted to 12 pages. Detailed submission instructions will be available at http://haskell.org/haskell-workshop/2007. Accepted papers will be published by the ACM and will appear in the ACM Digital Library. If there is sufficient demand, we will try to organise a time slot for system or tool demonstrations. If you are interested in demonstrating a Haskell related tool or application, please send a brief demo proposal to Andres Loeh (loeh at informatik.uni-bonn.de). Program Committee * Lennart Augustsson, Credit Suisse, UK * Derek Dreyer, Toyota Technological Institute at Chicago, US * Patricia Johann, Department of Computer Science, Rutgers University, US * Gabriele Keller, School of Computer Science and Engineering, University of New South Wales (Program Chair), Australia * Andy Gill, Galois, US * Stephanie Weirich , School of Engineering and Applied Science, University of Pennsylvania, US * Ganesh Sittampalam, Credit Suisse, UK * Ross Patterson, Programming Languages and Systems Group, City University London, UK * Doaitse Swierstra, Department of Computer Science, Utrecht University, The Netherlands * Chung-chieh Shan, Department of Computer Science, Rutgers University, US -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Dr. Gabriele Keller, Senior Lecturer Tel: +61-2-9385-6032 School of Computing Sciences & Engineering Fax: +61-2-9385-5995 University of New South Wales NSW 2052 Australia

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Type problems
by unknown＠example.com 11 Mar '07

11 Mar '07

I am stumped trying to print values returned from IO functions. How to print values returned from getEnv and getEnvironment? Thanks, Dave Feustel

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Announcing harchive-0.2: Backup and restore software in Haskell.
by David Brown 10 Mar '07

10 Mar '07

Announcing release 0.2 of "harchive", a program for backing up and restoring data. I've included a brief feature list below. The code is available in darcs at: http://www.davidb.org/darcs/harchive/ The package is available from hackage at: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/harchive-0.2 This release fixes some serious problems with the 0.1 release. No significant features have been implemented, but the code can now be compiled with '-O' without causing segfaults. Dave Brown ---------------------------------------------------------------------- Harchive version 0.2: - Several changes that change the storage format: - Changed protocol and storage format a bit to not encode lengths with hashes. - Record attributes of root directory. - Fix some problems with multiple threads on the SQL binding. There is still a problem, but by only using one OS thread, it doesn't appear now. Multiple simultaneous clients appear to work.

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CFP: HLPP 2007 (Tokyo, July 23-24, 2007)
by Zhenjiang Hu 09 Mar '07

09 Mar '07

We apologize if you receive multiple copies. --------------------------------------------------------------- Call For Papers Fourth International Workshop on HIGH-LEVEL PARALLEL PROGRAMMING AND APPLICATIONS (HLPP 2007) The University of Tokyo, Tokyo, Japan July 23-24, 2007 http://f.loulergue.free.fr/HLPP/hlpp2007/ --------------------------------------------------------------- AIMS AND SCOPE Bill McColl's post Sequential Computing Considered Harmful is an excellent summary of today's situation (http://www.computingatscale.com) Sequential computing cannot go further. Major companies in the computing industry now recognizes the urgency of reorienting an entire industry towards massively parallel computing. The trend is towards the increase of cores in processors and the need for scalable computing everywhere. But parallel and distributed programming is still dominated by low-level techniques such as send/receive message passing. Thus high-level approaches should play a key role in the shift to scalable computing in every computer. This workshop follows the first three HLPP workshops held in 2001, 2003 and 2005. It is aimed at: - computer science researchers, practitioners, graduate students - scientific computing researchers, practitioners, graduate students - high-performance application developers (e.g. in DBMS, data-mining, parallel model checking, virtual reality) TOPICS We welcome submission of original, unpublished papers in English on topics including (but not limited to) the following aspects of multi-core, concurrent, parallel, distributed, meta and grid computing: - high-level algorithms for parallel, communication-efficient and external-memory computation - high-level programming models (BSP, CGM, LogP, MPM, etc.) and tools - high-level programming models, tools and algorithms for multi-threaded, reconfigurable and multi-core computing - parallel programming methodologies - algorithmic skeletons and constructive methods - performance models and performance evaluation - high level resource-aware approaches object, functional, logic, constraint programming (semantics and implementation) - verification of parallel and distributed programs - security in high-level approaches - applications using high-level languages and tools (scientific computing, DBMS, model-checking, virtual reality, ...) - teaching experience with high-level tools and methods Accepted papers should be presented at the workshop. Revised versions will be published in a special issue of an international journal (previous HLPP workshops were published in Parallel Processing Letters, World Scientific Publishing) provided revisions suggested by the referees are made. IMPORTANT DATES 15 April 2007: Full paper due 28 May 2007: Notification 2 July 2007: Camera-ready paper due 23-24 July 2007: Workshop 17 September 2007: Journal version due PROGRAMME COMMITTEE Manuel Chrakravarty (Univ. of New South Wales, Australia) Murray Cole (Univ. of Edinburgh, UK) Alexandros Gerbessiotis (NJIT, USA) Sergei Gorlatch (Univ. of Muenster, Germany) Zhenjiang Hu (Univ. of Tokyo, Japan) Christoph Kessler (Linkopings Universitet, Sweden) Herbert Kuchen (Univ. of Muenster, Germany) Rita Loogen (Univ. of Marburg, Germany) Frederic Loulergue (Univ. of Orleans, France) Quentin Miller (Somerville College, Oxford, UK) Susanna Pelagatti (Univ. of Pisa, Italy) Alexander Tiskin (Univ. of Warwick, UK) Kazunori Ueda (Waseda University, Japan) CHAIRS AND ORGANIZERS Zhenjiang HU Information Processing Laboratory Department of Mathematical Informatics Department of Mathematical Engineering and Information Physics The University of Tokyo Frederic LOULERGUE Laboratoire d'Informatique Fondamentale d'Orleans Faculty of Sciences Computer Science Department University of Orleans PAST HLPP WORKSHOPS HLPP 2005 was held in Coventry (July 4-5, 2005). HLPP 2003 was held in Paris (June 16-18, 2003). Parallel Processing Letters (Volume 13, issue 3) contains 14 revised papers presented at the workshop. HLPP 2001 was held in Orleans (March 26-27, 2001). Parallel Processing Letters (Volume 11,issue 4) contains 8 revised papers presented at the workshop.

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Summer of Code questions
by Wolfgang Jeltsch 09 Mar '07

09 Mar '07

Hello, I’ve some questions regarding the Haskell.org involvement in the Google Summer of Code. First, what organization is “Haskell.org”? Is this a real organization, i.e., a legal entity? Does Haskell.org get the $ 500 for each successful project? If yes, what does Haskell.org do with this money? Furthermore, the Google Summer of Code FAQ talks about *the* project of a organization which seems to indicate that each organization has only one SoC project. What is the project of the Haskell.org organization then? Is this the general project “The Haskell language plus associated libraries and tools”? The FAQ says “Mentor organizations must be organizations or individuals running an active and viable open source or free software project”. Does this mean that the above-mentioned general project has to be active and viable (which it is) or that each concrete idea has to be part of an active and viable project? That is, is it allowed to start a new concrete project by letting a student code for it as part of the SoC or wouldn’t this be possible since a new project isn’t yet active and viable? Who decides which ideas will be worked on and who decides which student works on which? What are the obligations of a mentor? Is it okay to create an idea, become the mentor for this idea and propose a concrete student for it? What do I have to do to become a mentor? What are Haskell.org’s criteria for selecting mentors? According to the above-mentioned FAQ, Google wants to know these criteria as specifically as possible. Finally, should the ideas chosen so that they are solvable by a student working full time on them during the three months of the SoC? The problem is that at many German universities lectures go until July. At our university, for example, lecture time ends in mid of July and is followed by two weeks for exams. So a faithful student would only have the last month for working full time on the SoC. Thank you very much for any clarifications. Best wishes, Wolfgang

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