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ANN: diagrams 0.2
by Brent Yorgey 31 Jan '09

31 Jan '09

I am very pleased to announce the 0.2 release of the diagrams package, an embedded domain-specific language for creating simple graphics in a compositional style. This release includes a number of significant new features, including: * support for arbitrary straight and curved paths * more shape primitives, including polygons and rounded rectangles * support for rendering text * PNG, PDF, PS, and SVG output * built-in color support replaced with external dependence on the feature-rich colour library and many more! More information, examples, and installation instructions can be found at http://code.haskell.org/diagrams. More features are planned for future releases, so contributions and suggestions are welcome. (Please note: since diagrams depends on the Cairo library, which has unfortunately not been Cabalized, you cannot install the diagrams library with cabal-install, unless you already have the cairo package installed. See the above website for instructions.) A special thanks to Dougal Stanton for his contributions to the library and help in preparing this release. -Brent

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Jane Street Summer Project 2009
by yminsky 31 Jan '09

31 Jan '09

I'm pleased to announce the Jane Street Summer Project for 2009. The goal of the JSSP is to make functional programming languages into better practical tools for programming in the real world. To do that, we will fund students over the summer to work on open-source projects which aim at improving the practical utility of their favorite functional language. The JSSP is a follow-on to last year's OCaml Summer Project. A key difference this year is that we are opening up the project to proposals in languages other than OCaml (although we expect to maintain a focus on OCaml projects.) There are also some changes to the funding structure that are particularly relevant for projects located in the US. If you want to find out more, you can look at the JSSP blog: http://janestreetsummer.com And at the project FAQ: http://ocaml.janestreet.com/?q=node/57 We're looking forward to a great and productive summer, and we hope some of you come along for the ride! Thanks, Yaron Minsky

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Haskell Weekly News: Issue 103 - January 31, 2009
by Brent Yorgey 31 Jan '09

31 Jan '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20090131 Issue 103 - January 31, 2009 --------------------------------------------------------------------------- Welcome to issue 103 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements HDBC v2.0 now available. John Goerzen [2]announced that [3]HDBC v2.0 is now available. Simultaneously, [4]HDBC-sqlite3, [5]HDBC-postgresql, and [6]HDBC-odbc v2.0 have also been uploaded to Hackage. A guide to new features and migration can be [7]found here. Extensible and Modular Generics for the Masses: emgm-0.2. Sean Leather [8]announced the second major release of [9]Extensible and Modular Generics for the Masses (EMGM), a library for generic programming in Haskell using type classes and a sum-of-products view. Improvements over emgm-0.1 include type representation derivation using Template Haskell, documentation improvements, a bimap function, and more. incremental-sat-solver. Sebastian Fischer [10]announced the [11]incremental-sat-solver library, which provides an implementation of the [12]Davis-Putnam-Logemann-Loveland algorithm for the Boolean satisfiability problem. It not only allows solving Boolean formulas in one go, but also adding constraints and query bindings of variables incrementally. data-spacepart - space partitioning data structure[s] (initial release). Corey O'Connor [13]announced the [14]data-spacepart package, the goal of which is to be a collection of space partitioning data structures. Currently, there is only a simple quadtree implementation. Wired 0.2. Emil Axelsson [15]announced a new release of [16]Wired. The most important news in this release is that it now contains a 45nm cell library, which means that you can use Wired to create and analyze modern VLSI designs today! CFP Haskell Symposium 2009. Stephanie Weirich [17]announced a call for papers for the [18]2009 Haskell Symposium in Edinburgh, Scotland. The deadline for submissions is May 8. testpack (first release). John Goerzen [19]announced the release of [20]testpack, a collection of a few utilities for tests: some tools to convert QuickCheck properties into HUnit test cases, and various shortcuts and tools to increase verbosity while running tests in both QuickCheck and HUnit. convertible (first release). John Goerzen [21]announced a new package, [22]convertible. At its heart, it's a very simple typeclass that's designed to enable a reasonable default conversion between two different types without having to remember a bunch of functions. The return type from this conversion is "Either ConvertError a", and conversions are expected to do sanity checking (such as bounds checking when converting to types like Int), so as to produce neither garbage nor exceptions as part of the conversion process. The package also includes instances of the Convertible typeclass for common type conversions. working with numeric types as well as dates and times. Notably, it has code to convert between System.Time types and their Data.Time siblings, and vice versa, a capability I found annoyingly lacking in the standard library. Progress with IDE. Juergen Nicklisch-Franken [23]announced that the [24]Leksah 0.4.0 pre-release is now available. Current features include a Haskell customized editor with candy, project management support based on Cabal, a visual editor for Cabal files, navigation aids, a module browser, session support, and more. Hayoo! beta 0.3. Timo B. [25]announced the next beta version 0.3 of [26]Hayoo!, the Haskell API search engine with find-as-you-type and suggestions. Hayoo! now works even if your browser does not support JavaScript. DecisionTree 0.0. Adrian Neumann [27]announced the [28]DecisionTree package, which provides an implementation of the ID3 algorithm and can be used to classify data with discrete valued attributes. orchid-0.0.7. Sebastiaan Visser [29]announced a new release of [30]Orchid, just another Haskell Wiki. This release features a number of improvements, including a [31]filestore backend, searching, deleting and renaming support, and more. Check out the [32]demo. gitit 0.5. John MacFarlane [33]announced the latest release of [34]Gitit, the multitalented distributed wiki written in Haskell. This release uses the [35]filestore library and hence also supports a darcs backend, and also features optimizations, better search, better diffs, and more. You can check out a [36]running example. filestore 0.1. Gwern Branwen [37]announced [38]filestore 0.1, which provides a uniform, abstract, generic interface for storing versioned files on disk. It allows calling programs to use generic commands to store strings or binary data and perform various queries, such as 'what files are in this repository?' or 'what were the contents of this file at revision XXXXXXX?' or 'give me a diff of this file between revision XXXXXXX and revision YYYYYYY.' Because the interface is abstract, the calling program is insulated from the messy details of the backend (which might be a VCS or a database). Darcs and Git are fully supported. There are plans for a SQLite backend. Scurry :: A cross platform (if you put your mind to it) P2P VPN. John Van Enk [39]announced the release of [40]Scurry, a P2P VPN application written in Haskell (and a little C). Discussion Why binding to existing widget toolkits doesn't make any sense. Achim Schneider began an interesting [41]discussion on the proper approach to GUI toolkits in Haskell. Laws and partial values. Henning Thielemann began [42]a long thread on the semantics of laws (such as the monoid laws). Blog noise [43]Haskell news from the [44]blogosphere. * Sebastian Fischer: [45]Using SmallCheck to Shatter an Audacious Claim. * Xmonad: [46]Quad head xmonad. * Darcs: [47]darcs weekly news #15. * Osfameron: [48]More longest paths, and sick folds.. * Eric Kow (kowey): [49]haskell-ji. * Jeff Heard: [50]Control.Monad.IfElse. * Conal Elliott: [51]What is automatic differentiation, and why does it work?. * Luke Palmer: [52]Fun with PiSigma. * Neil Mitchell: [53]Small scripts with Haskell. * LHC Team: [54]Release notes.. * LHC Team: [55]Thoughts on a new code generator. * Xmonad: [56]contribs review: ThreeColumnsMiddle, CenteredMaster, Mosaic. * Osfameron: [57]There's the nub (snippet in Perl and Haskell). * Malcolm Wallace: [58]codec implementations. * Sebastian Fischer: [59]Fun with Infinite Global Constants. Just-in-time, memoized binomial coefficients. * Chris Done: [60]Some libgd changes. * Luke Palmer: [61]A world without orphans. Luke muses on the benefits to be gained by outlawing orphan instances. * Creighton Hogg: [62]Fear of releasing code. * LHC Team: [63]Thoughts on a new code generator. * Don Stewart (dons): [64]What is Haskell good for?. Lots of things, if this tag cloud has anything to say about it. * Arch Haskell News: [65]Haskell wiki stack in Arch. * Conal Elliott: [66]Comparing formulations of higher-dimensional, higher-order derivatives. * Conal Elliott: [67]Fostering creativity by relinquishing the obvious. * Arch Haskell News: [68]Arch Haskell News: Jan 11 2009. * Dan Piponi (sigfpe): [69]Fast incremental regular expression matching with monoids. A very cool article showing how to use fingertrees storing memoized automaton transition functions to do fast incremental regular expression matching (or, in general, fast incremental lexing). Quotes of the Week * lilac: is happy with his infinite type. it's ducks all the way across and down. * Gracenotes: You are likely to be eaten by a poset * RossMellgren: Apparently 64-bit GHC is sufficiently advanced to be indistinguishable from magic. * cjb: It's all fun and games until somebody loses an IOVar. * sigfpe: If I took some Ritalin, maybe I could write an entire book on Haskell and algebra. * ddarius: Nothing is evaluated until it is. About the Haskell Weekly News New editions are posted to [70]the Haskell mailing list as well as to [71]the Haskell Sequence and [72]Planet Haskell. [73]RSS is also available, and headlines appear on [74]haskell.org. To help create new editions of this newsletter, please see the information on [75]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [76]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51664 3. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC 4. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dsqlite3 5. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dpostgresql 6. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dodbc 7. http://software.complete.org/software/wiki/hdbc/NewIn20 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51646 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51564 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/incremental-sat-… 12. http://en.wikipedia.org/wiki/DPLL_algorithm 13. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51505 14. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/data-spacepart 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51484 16. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Wired 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16818 18. http://haskell.org/haskell-symposium/2009/ 19. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51482 20. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/testpack 21. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51481 22. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/convertible 23. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51475 24. http://www.leksah.org/ 25. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51450 26. http://holumbus.fh-wedel.de/hayoo 27. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51407 28. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/DecisionTree 29. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51395 30. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/orchid 31. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 32. http://funct.org/wiki/ 33. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51392 34. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/gitit 35. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 36. http://gitit.johnmacfarlane.net/ 37. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51388 38. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 39. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51364 40. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Scurry 41. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/51478 42. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/51299 43. http://planet.haskell.org/ 44. http://haskell.org/haskellwiki/Blog_articles 45. http://www-ps.informatik.uni-kiel.de/~sebf/haskell/smallcheck-experience.ht… 46. http://xmonad.wordpress.com/2009/01/31/quad-head-xmonad/ 47. http://blog.darcs.net/2009/01/darcs-weekly-news-15.html 48. http://greenokapi.net/blog/2009/01/31/more-longest-paths-and-sick-folds/ 49. http://koweycode.blogspot.com/2009/01/haskell-ji.html 50. http://vis.renci.org/jeff/?p=96 51. http://conal.net/blog/posts/what-is-automatic-differentiation-and-why-does-… 52. http://lukepalmer.wordpress.com/2009/01/28/fun-wth/ 53. http://neilmitchell.blogspot.com/2009/01/small-scripts-with-haskell.html 54. http://lhc-compiler.blogspot.com/2009/01/release-notes.html 55. http://lhc-compiler.blogspot.com/2009/01/thoughts-on-new-code-generator.html 56. http://xmonad.wordpress.com/2009/01/27/contribs-review-threecolumnsmiddle-c… 57. http://greenokapi.net/blog/2009/01/27/theres-the-nub-snippet-in-perl-and-ha… 58. http://feeds.feedburner.com/~r/malcolm/~3/523603226/codec-implementations.h… 59. http://www-ps.informatik.uni-kiel.de/~sebf/haskell/infinite-constants.html 60. http://chrisdone.com/blog/2009/01/26/Some-libgd-changes 61. http://lukepalmer.wordpress.com/2009/01/25/a-world-without-orphans/ 62. http://abstractabsurd.blogspot.com/2009/01/fear-of-releasing-code.html 63. http://lhc-compiler.blogspot.com/2009/01/thoughts-on-new-code-generator.html 64. http://donsbot.wordpress.com/2009/01/24/what-is-haskell-good-for/ 65. http://archhaskell.wordpress.com/2009/01/25/haskell-wiki-stack-in-arch/ 66. http://conal.net/blog/posts/comparing-formulations-of-higher-dimensional-hi… 67. http://conal.net/blog/posts/fostering-creativity-by-relinquishing-the-obvio… 68. http://archhaskell.wordpress.com/2009/01/11/arch-haskell-news-jan-11-2009/ 69. http://sigfpe.blogspot.com/2009/01/fast-incremental-regular-expression.html 70. http://www.haskell.org/mailman/listinfo/haskell 71. http://sequence.complete.org/ 72. http://planet.haskell.org/ 73. http://sequence.complete.org/node/feed 74. http://haskell.org/ 75. http://haskell.org/haskellwiki/HWN 76. http://code.haskell.org/~byorgey/code/hwn/

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ANN: HDBC v2.0 now available
by John Goerzen 30 Jan '09

30 Jan '09

Hi everyone, I'm pleased to announce that HDBC v2.0 is now available. Simultaneously, HDBC-sqlite3, HDBC-postgresql, and HDBC-odbc v2.0 have also been uploaded. All may be found from Hackage, or at software.complete.org. A guide to new features and migration can be found at: http://software.complete.org/software/wiki/hdbc/NewIn20 A partial summary of it follows: New Features: * Pervasive Unicode support now part of the HDBC API and implemented by all backend drivers. Based on utf8-string and conversions between UTF-8 ByteStrings and Haskell Strings. * Full support for GHC 6.10 is new. Full support for GHC 6.8 is maintained. * Native support for the new exception handling in GHC 6.10, with CPP conditional compilation to continue supporting the old-style exceptions for users of GHC 6.8 or Hugs. * HDBC now has direct support for marshalling virtually all of the Data.Time.* types to and from SQL database date/time types. toSql and fromSql/safeFromSql now support conversions between Data.Time.* types and SqlValue. Conversions between System.Time.* types were present from the beginning and will remain. Automatic conversions are, of course, contingent on support in database engines and HDBC database backend drivers and may not be possible with all databases. * Major expansion of SqlValue to be able to carry date/time data to/from databases in terms of Data.Time.* types. + The old SqlTimeDiff and SqlEpochTime types continue to be present, but are deprecated and will be removed in a future. toSql no longer converts anything to them. The System.Time.* types are converted to the new Data.Time-based SqlValues. It should be exceptionally rare that any user code would use these types directly, but they are being retained in this version out of an abundance of caution. * Replace fromSql with safeFromSql, which returns Left on impossible conversions instead of raising an exception. + Wrote a new fromSql that behaves just like the old one, but is implemented in terms of safeFromSql. It converts the safeFromSql errors to exceptions. + The new structure made it possible to greatly enhance many error messages throughout the conversion process instances. + Removed SqlType typeclass. Re-implemented SqlValue conversions in terms of the generic infrastructure in the convertible package. Simplified code significantly due to this. * Lots of additional docs. * New skeleton test suite for HDBC itself (to be expanded upon later). Richer Date and Time Support HDBC 1.x had only two ways of getting dates and times between Haskell and a database: an epoch (an Integer representing the number of seconds since midnight Jan 1 1970 UTC) and an Integer representing a TimeDiff (a count of elapsed time). While this approach could represent a precise instant in time, it was not always the most helpful. Most notably, you might sometimes want to load date information without time, time without date, or record what timezone the time was measured within. HDBC can now convert all of these things with much greater precision. Thanks to Phil Wise for adding the first Unicode support (to HDBC-postgresql originally) and to Alson Kemp for adding the first advanced date/time marshalling support (also to HDBC-postgresql originally). The experience of adding these features to a single backend driver first made clear a good way to add them to HDBC API as a whole. -- John

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ANNOUNCE: Extensible and Modular Generics for the Masses: emgm-0.2
by Sean Leather 30 Jan '09

30 Jan '09

============================================== Extensible and Modular Generics for the Masses ============================================== Extensible and Modular Generics for the Masses (EMGM) is a library for generic programming in Haskell using type classes and a sum-of-products view. ------------ Introduction ------------ emgm-0.2 is the second major release of the EMGM library. A lot of work has been done since the initial release to build a solid set of functions that will allow you to derive the necessary declarations for using EMGM with your datatype. Thus, you don't have to write much code to get started. A great deal of documentation has also been added. There's a comprehensive new entry page for Generics.EMGM that should help one figure out what to do with this library. We plan to publish articles providing more examples as well. With these two improvements, you have no more excuses for not trying it out. Download EMGM and see what you can do, generically! ------------ New Features ------------ Improvements over emgm-0.1 include: * Derive type representation using Template Haskell [1] * Major improvement in documentation with Haddock * bimap function [2] [1] Here is a snippet from the documentation that shows what you save when using TH over manual implementation. > {-# LANGUAGE TemplateHaskell #-} > {-# LANGUAGE MultiParamTypeClasses #-} > {-# LANGUAGE FlexibleContexts #-} > {-# LANGUAGE FlexibleInstances #-} > {-# LANGUAGE OverlappingInstances #-} > {-# LANGUAGE UndecidableInstances #-} > module Example where > import Generics.EMGM > data T a = C a Int > $(derive ''T) The $(derive ''T) declaration in the above example generates the following code: 1. Constructor description declarations (1 per constructor) > conC :: ConDescr > conC = ConDescr "C" 2 [] Nonfix 2. Embedding-projection pair declarations (1 per type) > epT :: EP (T a) (a :*: Int) > epT = EP fromT toT > where fromT (C v1 v2) = v1 :*: v2 > toT (v1 :*: v2) = C v1 v2 3. Rep instance (1 per type) > instance (Generic g, Rep g a, Rep g Int) => Rep g (T a) where > rep = rtype epT (rcon conC (rprod rep rep)) 4. Higher arity instances if applicable (either FRep, FRep2, and FRep3 together, or BiFRep2) > instance (Generic g) => FRep g T where > frep ra = rtype epT (rcon conC (rprod ra rint)) In this case, similar instances would be generated for FRep2 and FRep3. 5. Function-specific instances (1 per type) > instance Rep (Collect Char) Char where > rep = Collect (:[]) [2] EMGM has a new function bimap and its related representation type class BiFRep2: > bimap :: (BiFRep2 Map f) => (a -> c) -> (b -> d) -> f a b -> f c d With bimap, you can do the following in GHCi: *Generics.EMGM Data.Char Prelude> bimap ord chr ('a',65) (97,'A') *Generics.EMGM Data.Char Prelude> bimap (++" So Long!") (const 42) (Right "Earth") Right 42 ------------------- General Information ------------------- Visit the home page: http://www.cs.uu.nl/wiki/GenericProgramming/EMGM ---------------- General Features ---------------- The primary features of EMGM include: * Datatype-generic programming using sum-of-product views * Large collection of ready-to-use generic functions * Included support for standard datatypes: lists, Maybe, tuples * Easy to add support for new datatypes * Type classes make writing new functions straightforward in a structurally inductive style * Generic functions are extensible with ad-hoc cases for arbitrary datatypes * Good performance of generic functions The features of this distribution include: * The API is thoroughly documented with Haddock * Fully tested with QuickCheck and HUnit * Program coverage ensures that all useful code has been touched by tests * Tested on both Mac and Windows systems ------------ Requirements ------------ EMGM has the following requirements: * GHC 6.8.1 - It has been tested with versions 6.8.3 and 6.10.1 * Cabal library 1.2.1 - It has been tested with versions 1.2.4.0 and 1.6.0.1. ----------------- Download & Source ----------------- Use caball-install: cabal install emgm Get the package: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm Check out the current source with Subversion: svn checkout https://svn.cs.uu.nl:12443/repos/dgp-haskell/EMGM/trunk Or view it online: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/ -------- Examples -------- Check out the examples: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/examples/ -------------- Bugs & Support -------------- Report issues or request features: http://code.google.com/p/emgm/issues/list Discuss EMGM with the authors, maintainers, and other interested persons: http://www.haskell.org/mailman/listinfo/generics ------- Credits ------- The research for EMGM originated with Ralf Hinze. It was extended with work by Bruno Oliveira and Andres Löh. More details of the library functionality were explored by Alexey Rodriguez. We are very grateful to all of these people for the foundation on which this library was built. The current authors and maintainers of EMGM are: * Sean Leather * José Pedro Magalhães * Alexey Rodriguez * Andres Löh

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CFP Haskell Symposium 2009
by Stephanie Weirich 29 Jan '09

29 Jan '09

Haskell 09 ACM SIGPLAN Haskell Symposium 2009 Edinburgh, Scotland, UK September 3, 2009 CALL FOR PAPERS http://haskell.org/haskell-symposium/2009/ The ACM SIGPLAN Haskell Symposium 2009 will be co-located with the 2009 International Conference on Functional Programming (ICFP). The purpose of the Haskell Symposium is to discuss experiences with Haskell and future developments for the language. The scope of the symposium 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 Haskellers can benefit. It is not enough simply to describe a program! Before 2008, the Haskell Symposium was known as the Haskell Workshop. The name change reflects both the steady increase of influence of the Haskell Workshop on the wider community as well as the increasing number of high quality submissions. The acceptance process is highly competitive. After eleven Haskell Workshops between 1995 and 2007, the first Haskell Symposium was held in Victoria in 2008. Submission Details * Submission Deadline: Friday, May 8th 2009 (3:00 pm, Eastern US Time) * Author Notification: Monday, June 1st 2009 * Final Papers Due : Monday, June 15th 2009 Submitted papers should be in portable document format (PDF), formatted using the ACM SIGPLAN style guidelines (http://www.acm.org/sigs/sigplan/authorInformation.htm) The length is restricted to 12 pages, and the font size 9pt. Each submission must adhere to SIGPLAN's republication policy, as explained on the web. Violation risks summary rejection of the offending submission. 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 organize 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 Stephanie Weirich, sweirich(a)cis.upenn.edu. Links * http://haskell.org/haskell-symposium, the permanent homepage of the Haskell Symposium. * http://haskell.org/haskell-symposium/2009/, the 2009 Haskell Symposium web page. * http://www.icfpconference.org/icfp2009, the ICFP 2009 web page. Program Committee * Jeremy Gibbons, Oxford University * Bastiaan Heeren, Open Universiteit Nederland * John Hughes, Chalmers/Quviq * Mark Jones, Portland State University * Simon Marlow, Microsoft Research * Ulf Norell, Chalmers * Chris Okasaki, United States Military Academy * Ross Paterson, City University London * Alexey Rodriguez Yakushev, Vector Fabrics * Don Stewart, Galois * Janis Voigtlaender, TU Dresden * Stephanie Weirich, University of Pennsylvania (Chair)

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Last CfP: WWV 2009
by demis＠dimi.uniud.it 28 Jan '09

28 Jan '09

[Apologies if you receive multiple copies] *********************************************************** * CALL FOR PAPERS * * * * WWV 2009 * * Automated Specification and Verification of Web Systems * * 5th International Workshop * * * * Castle of Hagenberg, Austria. July 17, 2009 * * http://www.risc.uni-linz.ac.at/conferences/wwv09/ * * * * Part of the RISC Summer 2009 * * http://www.risc.uni-linz.ac.at/conferences/summer2009/ * *********************************************************** IMPORTANT DATES Abstract Submission February 2, 2009 Full Paper Submission February 9, 2009 Acceptance Notification April 20, 2009 Camera Ready June 1, 2009 Workshop July 17, 2009 SCOPE 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 formal methods and techniques applied to Web sites, Web services or Web-based applications, such as: * rule-based approaches to Web site analysis, certification, specification, verification, and optimization * algebraic methods for verification and certification of Web systems * formal models for describing and reasoning about Web sites * model-checking, synthesis and debugging of Web sites * 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 The WWV series provides a forum for researchers from the communities of Rule-based programming, Automated Software Engineering, and Web-oriented research to facilitate the cross-fertilization and the advancement of hybrid methods that combine the three areas. The previous WWV editions were: WWV'08 (Siena, Italy), WWV'07 (Venice, Italy), WWV'06 (Paphos, Cyprus), and WWV'05 (Valencia, Spain). LOCATION WWV'09 will be held at the Research Institute for Symbolic Computation (RISC), which is an institute of the Johannes Kepler University in Linz. It is located in the Castle of Hagenberg, a romantic, medieval castle amidst the lovely, hilly landscape of the Mühlviertel region, 20 km north east of Linz, the provincial capital of Upper Austria, located halfway between Salzburg and Vienna. For more information about RISC, please visit: http://www.risc.uni-linz.ac.at/ The workshop is a part of the RISC Summer 2009 conference series: http://www.risc.uni-linz.ac.at/about/conferences/summer2009/ SUBMISSION PROCEDURE Submissions must be received by February 9, 2009. In addition, an ASCII version of the title and abstract must be submitted by February 2, 2009. Submitted papers should be prepared in LaTeX, formatted according to the Springer llncs style, and should not exceed 15 pages. Submission is web-based via this link: http://www.easychair.org/conferences/?conf=wwv09 PUBLICATION Accepted papers will be published in a preliminary proceedings volume, which will be available during the workshop. After the workshop, a special issue of the Journal of Symbolic Computation on the topic of the WWV workshop is planned. PROGRAM CO-CHAIRS Demis Ballis University of Udine, Italy Temur Kutsia Johannes Kepler University Linz, Austria WORKSHOP CO-CHAIRS Temur Kutsia Johannes Kepler University Linz, Austria Wolfgang Schreiner Johannes Kepler University Linz, Austria INVITED SPEAKERS François Bry Ludwig Maximilian University of Munich, Germany Axel Polleres National University of Ireland, Galway, Ireland PROGRAM COMMITTEE Maria Alpuente Technical University of Valencia, Spain Demis Ballis University of Udine, Italy Wlodzimierz Drabent Linköping University, Sweden, and Institute Of Computer Science, Polish Academy of Sciences, Poland Santiago Escobar Technical University of Valencia, Spain Moreno Falaschi University of Siena, Italy Mário Florido University of Porto, Portugal Temur Kutsia Johannes Kepler University Linz, Austria Massimo Marchiori University of Padova, Italy Mircea Marin University of Tsukuba, Japan Catherine Meadows Naval Research Laboratory, USA Rosario Pugliese University of Florence, Italy I.V. Ramakrishnan Stony Brook University, USA Antonio Vallecillo University of Malaga, Spain

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type inference & instance extensions
by oleg＠okmij.org 27 Jan '09

27 Jan '09

Doug McIlroy wrote: > A fragment of an attempt to make pairs serve as complex numbers, > using ghc/hugs extensions: > > instance Num a => Num (a,a) where > (x,y) * (u,v) = (x*u-y*v, x*v+y*u) > > Unfortunately, type inference isn't strong enough to cope with > > (1,1)*(1,1) It is not quite difficult to tell the type checker that if pairs of numbers are numbers, the two components of the pair must have the same type. We say so literally. We first should make the instance more general to permit any pair, of the type (a,b) to match. We next impose the constraint that the types a and b must be in the class Num; furthermore, the types a and b must be the same. Here is the complete solution that should work on GHC 6.4, 6.6, 6.8, and probably of earlier and later versions. > {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, > UndecidableInstances, FlexibleInstances #-} > > module D where > > instance (Num a, Num b, TypeCast b a, TypeCast a b) => Num (a,b) where > (x,y) * (u,v) = (typeCast x * typeCast u - typeCast y * typeCast v, > typeCast x * typeCast v + typeCast y * typeCast u) > (x,y) + (u,v) = (typeCast x + typeCast u, > typeCast y + typeCast v) > (x,y) - (u,v) = (typeCast x - typeCast u, > typeCast y - typeCast v) > fromInteger x = (fromInteger x, 0) > > test1 = (1,1) * (2,2) -- (0.0,4.0) > test2 = (1.1,1) * (2,2) -- (0.20000000000000018,4.2) > test3 = test1 * test2 -- (-16.8,0.8000000000000007) > test4 = (test1 + test3) * (test1 - test3) -- (-297.6,26.880000000000024) > test4' = -16 - test3 * test3 -- (-297.6,26.880000000000024) > > class TypeCast a b | a -> b, b->a where typeCast :: a -> b > class TypeCast' t a b | t a -> b, t b -> a where typeCast' :: t->a->b > class TypeCast'' t a b | t a -> b, t b -> a where typeCast'' :: t->a->b > instance TypeCast' () a b => TypeCast a b where typeCast x = typeCast' () x > instance TypeCast'' t a b => TypeCast' t a b where typeCast' = typeCast'' > instance TypeCast'' () a a where typeCast'' _ x = x As one can see, we added typeCast before every variable, indicating that an application of the equality constraint is needed. We let the GHC figure out what should be `cast' to what. The recent versions of GHC have a nifty equality constraint, so the code can be written simply > {-# LANGUAGE TypeFamilies #-} > > {-# OPTIONS -fglasgow-exts #-} > {-# OPTIONS -fallow-undecidable-instances #-} > > module D where > > instance (Num a, Num b, a ~ b) => Num (a,b) where > (x,y) * (u,v) = (x*u-y*v, x*v+y*u) > > test1 = (1,1) * (2,2) It does typecheck in GHC 6.8.2; alas, running the code produces > ghc-6.8.2: panic! (the 'impossible' happened) > (GHC version 6.8.2 for i386-unknown-freebsd): > nameModule $dNum{v aJiF} I guess one needs to upgrade to GHC 6.10. The solution using TypeCast, however inelegant, works on GHC 6.8 and earlier compilers.

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ANN: Hayoo! beta 0.3
by Timo B. Hübel 25 Jan '09

25 Jan '09

Hello! We are pleased to announce the next beta version 0.3 of Hayoo!, the Haskell API search engine with find-as-you-type and suggestions. Visit Hayoo! here: http://holumbus.fh-wedel.de/hayoo Basically, there is one new major feature available: Hayoo! now works even if your browser does not support JavaScript. Of course, this means that you won't have the find-as-you-type functionality, but everything else will be available. Hence everybody who has been scared away from Hayoo! because of all this crazy AJAX stuff now has no excuse anymore for not using Hayoo! ;-) Along the way we fixed several minor bugs and slightly improved the ranking algorithm as well as the help page. Since the last official announcement we were also able to bring back the source links. Still to come in the next weeks is a major index update to reflect the incredible package growth on Hackage. Please let us know about any problems, hints and suggestions. Happy hacking, Timo

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ANN: filestore 0.1
by Gwern Branwen 25 Jan '09

25 Jan '09

ANN filestore 0.1 We are pleased to announce the first release of a new library, filestore. What is it? filestore provides a uniform, abstract, generic interface for storing versioned files on disk. It allows calling programs to use generic commands to store strings or binary data and perform various queries, such as 'what files are in this repository?' or 'what were the contents of this file at revision XXXXXXX?' or 'give me a diff of this file between revision XXXXXXX and revision YYYYYYY.' Because the interface is abstract, the calling program is insulated from the messy details of the backend (which might be a VCS or a database). What backends are supported? Darcs and Git are fully supported. There are plans for a SQLite backend. What is this good for? Currently it is used by two wikis, Gitit and Orchid. We hope it will see use in other applications as well that need to version data and would like the various advantages of DVCSs (such as easy collaboration, advanced merging, etc.). Where can you get it? Your local cabal-install, Hackage at http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore and of course you can do 'darcs get http://johnmacfarlane.net/repos/filestore' for the very latest. filestore was written by John MacFarlane, Gwern Branwen, and Sebastiaan Visser -- gwern

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