May 2009 - Haskell-Cafe

GSoC project for EclipseFP
by Thomas ten Cate 15 May '09

15 May '09

Hi all, I'm happy to announce that my Google Summer of Code project proposal, titled "Extend EclipseFP functionality for Haskell", has been accepted! This means that I will be working on EclipseFP during the upcoming months. For the uninitiated, EclipseFP is a plugin for the Eclipse IDE that makes Haskell support possible. Currently it is fairly limited, but I hope to bring it to a state in which I can start using it for some larger projects of my own. "Live" type checking and type inference, and all that jazz. This will be powered by the Scion library by Thomas Schilling (nominolo), who is also my GSoC mentor. More information is on my new blog: http://eclipsefp.wordpress.com/ Cheers, Thomas

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ANN: RESTng 0.1 + RedHandlers 0.1 (request handlers) + YuiGrids 0.1 (yahoo grids)
by Sergio Urinovsky 15 May '09

15 May '09

I'd like to announce the release of 3 new packages in hackage developed for a RESTful web framework called RESTng. They are experimental, the framework is incomplete and we are currently not actively developing it. There are several interesting features so we have decided to release them to share the ideas. *RESTng:* A framework for writing RESTful applications. Features that may be of interest are: * Resource presentation with annotations (implemented with Grids): Resources are annotated with related data and all ends in boxes using grids. i.e., an annotation for a book resource could be its author (the author resource), and also their comments, so the book, the author and their comments are shown in boxes. Annotations can have arbitrary data, but there are some generic ones already available. * Hierarchical URLs are automatically handled. i.e.: Can easily define that a book resource "has many" chapters, then these actions are defined: GET http://site/book/3/chapter/1 (get the chapter 1 of book with id 3) GET http://site/book/3/chapter/new (get a form for filling data for the new chapter for book with id 3) POST http://site/book/3/chapter/new (create a new chapter for the book with id 3) and so on for updates, list and delete actions * ORM generates tables from haskell records (currently only PostgreSQL is supported in the ORM). * Associations "has many" defined for models. Making available functions to query for the parent and children so you don't have to make the SQL query. * Associations can be polymorphic so a comment can be associated to different resources types. A record for a comment on a book, another for a comment on a post. * Tags, Ratings, Comments, Users and login and CMS-like form fields validations supported. *YuiGrids:* * Containers and boxes with layout hints are specified. i.e: - Box A: in left side bar, near the bottom, with this content .... - Container B: in the main part of the page, near the top, with 3 columns and these let's say 14 boxes inside ... (including Box C) - Box C: in the left column of three, with this other content ... * Tries to satisfy the layout hints. Not allways possible, i.e: if every box has layout hint to go near the bottom, some of them will go at the top. * Boxes can have CSS specifications. * All is rendered into Yahoo grids (http://developer.yahoo.com/yui/grids) Currently, the YuiGrids uses own contextual html combinators are also implemented in this package (called CxML here) instead of Text.XHtml for keeping track of html parts like inline CSSs to be rendered at the head. This can be improved to use the standard Text.XHtml library. *RedHandlers:* It is another HTTP request handlers library to build standalone web apps. * They deal with request data as usual. * There are also combinators for mapping part of the URL to public folders in the file system. * And one for sending files efficiently in the response (a fork of the HTTP library was necessary for this, included here).

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Don't play with your monads...
by David Leimbach 15 May '09

15 May '09

eventually you'll go bind. Sorry couldn't resist.

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I have forgotten .. my bad
by Vasili I. Galchin 15 May '09

15 May '09

Hello, darcs get --init ....?????? I want to pull down Data.FiniteMap. I have forgotten the path to Hackage .. I tried .... sudo darcs get http://hackage.haskell.org/ Data.FiniteMap [sudo] password for vigalchin: Invalid repository: http://hackage.haskell.org darcs failed: Failed to download URL http://hackage.haskell.org/_darcs/inventory : HTTP error (404?) ?? Obviously the code I am cabalizing needs to be "upgraded"(i.e. not using deprecated packages) but first I want it to build! Thanks, Vasili

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TFM09: Last CFP (Formal Methods Week, Eindhoven, November 6th 2009)
by J.N. Oliveira 15 May '09

15 May '09

TFM2009 2nd Int. FME Conference on Teaching Formal Methods "Widening Access to Formal Methods" Friday, November 6th 2009, co-located with FM2009 : 16th International Symposium on Formal Methods Eindhoven, the Netherlands, November 2 - November 6, 2009 CALL FOR PAPERS (URL: http://www.di.uminho.pt/tfm09) 1. About the conference ----------------------- Ten years after the First World Formal Methods Congress (FM'99) in Toulouse, formal methods communities from all over the world will once again have an opportunity to come together. As part of the First Formal Methods Week event surrounding the FM2009 conference in Eindhoven, Formal Methods Europe will be organizing TFM2009, the Second International Conference on Teaching Formal Methods. The conference will serve as a forum to explore the successes and failures of Formal Methods (FM) education, and to promote cooperative projects to further education and training in FMs. We would like to provide a forum for lecturers, teachers, and industrial partners to discuss their experience, present their pedagogical methodologies, and explore best practices. TFM2009 follows in a series of recent events on teaching formal methods, including: two BCS-FACS TFM workshops (Oxford in 2003, and London in 2006), the TFM 2004 conference in Ghent (with proceedings published as Springer LNCS Volume 3294), the FM-Ed 2006 workshop (Hamilton, co-located with FM'06), FORMED (Budapest, at ETAPS 2008), FMET 2008 (Kitakyushu 2008, co-located with ICFEM), etc. 2. Topics of interest --------------------- Formal methods (FM) have an important role to play in the development of complex computing systems - a role acknowledged in industrial standards such as IEC 61508 and ISO/IEC 15408, and in the increasing use of precise modeling notations, semantic markup languages, and model-driven techniques. There is a growing need for software engineers who can work effectively with simple, mathematical abstractions, and with practical notions of inference and proof. However, there is little clear guidance ? for educators, for managers, or for the engineers themselves ? as to what might comprise a basic education in FM. Neither the present IEEE/ACM Software Engineering Body of Knowledge (SWEBOK) nor the forthcoming Graduate Software Engineering Reference Curriculum (GSWERC) provide the kind of specific information that teachers and practitioners need to establish an adequate, balanced programme of learning in FM. Original contributions are solicited that provide insight, opinions, and suggestions for courses of action regarding the teaching FMs, including but not limited to the following aspects: * experiences of teaching FMs, both successful and unsuccessful; * educational resources including the use of books, case studies and the internet; * the education of weak and mathphobic students; * the integration, or otherwise, of FMs into the curriculum, including contributions to the definition of a Formal Methods Body of Knowledge (FMBOK); * the advantages of FM-trained graduates in the workplace; * changing attitudes towards FMs in students, academic staff and practitioners; * the necessary mathematical background. The conference proceedings will be published by Springer-Verlag in the LNCS series. Submissions may be up to 20 pages long using Springer's LNCS format. 3. Important dates ------------------ Please put the following dates in your diary: Submission deadline May 25, 2009 Notification of acceptance July 6, 2009 Final version August 3, 2009 4. How to submit ---------------- Papers for TFM2009 will be processed through the EasyChair conference management system.To submit your paper, please visit: http://www.easychair.org/conferences/?conf=tfm2009 5. Invited speakers ------------------- To be announced 6. Programme Committee ---------------------- Izzat Alsmadi (North Dakota State University, USA) Dines Bjorner (IIMM Institute, Denmark) Eerke Boiten (University of Kent, UK) Raymond Boute (Universiteit Gent, Belgium) Andrew Butterfield (Trinity College, Dublin) Jim Davies (University of Oxford, UK) David Duce (Oxford Brookes University, UK) John Fitzgerald (University of Newcastle upon Tyne, UK) Jeremy Gibbons (University of Oxford, UK) Randolph Johnson (National Security Agency, USA) Michael Mac an Airchinnigh (Trinity College, Dublin) Dino Mandrioli (Politecnico di Milano, Italy) Jose Oliveira (Universidade do Minho, Portugal) Kees Pronk (Technische Universiteit Delft, NL) Bernhard Schaetz (Tecnical University of Munique, Germany) Wolfgang Schreiner (Johannes Kepler University Linz, Austria) Simao Melo de Sousa (Universidade da Beira Interior, Portugal) Kenji Taguchi (National Institute of Informatics, Japan) Jeannette Wing (Carnegie-Mellon University, USA) 7. Sponsorship ---------------------- TFM2009 is supported by FME, the Formal Methods Europe Association

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Re: Data.Binary and little endian encoding
by John Lato 15 May '09

15 May '09

leimy2k: > On Thu, May 14, 2009 at 8:46 PM, Don Stewart <dons(a)galois.com> wrote: > >> leimy2k: >> > >> > >> > On Thu, May 14, 2009 at 8:40 PM, Don Stewart <dons(a)galois.com> wrote: >> > >> > leimy2k: >> > > I actually need little endian encoding... wondering if anyone else >> hit >> > this >> > > with Data.Binary. (because I'm working with Bell Lab's 9P protocol >> which >> > does >> > > encode things on the network in little-endian order). >> > > >> > > Anyone got some "tricks" for this? >> > >> > Yes! >> > There are big, little and host-endian primitives in the Get/Put >> monads. >> > >> > >> http://hackage.haskell.org/packages/archive/binary/0.5.0.1/doc/html/ >> > Data-Binary-Put.html#v%3AputWord16le >> > >> > You can use these to build encoders directly. >> > >> > >> > Cool... I just have to write my own encoder and decoder now. >> > >> > As a request could we get encodeLe decodeLe for a later version of this >> > library? :-) That'd be totally awesome. >> >> Oh, you mean entirely different instances for all the current ones, that >> use LE encodings? >> > > Well the library is leaning towards "Network Byte Order" in that it has > encode/decode that only encode/decode for Big Endian. > > Us folks who have to do little endian all now have to write our own > encoding/decoding :-) > > I'm speaking specifically of the encode/decode functions. I have no idea > how they're implemented. The encode/decode functions just call the runGet/runPut functions for whatever is being encoded or decoded to combined with the get/put functions from the Binary instance. The endian-ness is entirely determined by the Binary instance for the data type you're encoding/decoding, not anything in the encode/decode functions themselves. For data types you define, you can make the Binary instance LE standard (although it may not be a good idea) by using the little-endian primitives Don mentioned. For built-in types, if you want to use a different endian-ness, you can make new get/put functions then call runGet/runPut on those directly. You won't be able to redefine the Binary instances, but if you'll be doing this with a lot of different types you could make your own BinaryLE class like this: class BinaryLE t where putLE :: t -> Put getLE :: Get t encodeLE :: BinaryLE a => a -> ByteString encodeLE = runPut . putLE decodeLE :: BinaryLE a => ByteString -> a decodeLE = runGet getLE I've done some work with Binary and little-endian, and this bias never really bothered me (I think it's actually a host-endian bias, could be mistaken). I was using my own data types so I had to make my own custom Binary instances, which I would have had to do anyway. The data format specified little-endian, so making the Binary instance LE-standard seemed appropriate. You'd only need to re-make custom get/put functions if you're using types that already have Binary instances, and you intend to manipulate the data outside of Haskell. Does that describe your situation? John

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ICFP09 Accepted Papers
by Matthew Fluet (ICFP Publicity Chair) 15 May '09

15 May '09

Accepted Papers ICFP 2009: International Conference on Functional Programming Edinburgh, Scotland, 31 August - 2 September 2009 http://www.cs.nott.ac.uk/~gmh/icfp09.html The ICFP 2009 Program Chair and Committee are pleased to announce that the following papers have been accepted for the conference. Additional information regarding the final program, invited speakers, and registration will be forthcoming. However, the Local Arrangements Co-Chairs would like to remind participants of the following: * ICFP'09 coincides with the final week of the Edinburgh International Festival, one of the premier arts and cultural festivals in the world. The opportunity to attend the Festival is a plus! Due to the popularity of Edinburgh during the festival period, we recommend booking accommodation early. More details regarding accommodation may be obtained from the ICFP 2009 Local Arrangements webpage: http://www.haskell.org/haskellwiki/ICFP_2009_Local_Arrangements Accepted papers ~~~~~~~~~~~~~~~ A CONCURRENT ML LIBRARY IN CONCURRENT HASKELL Avik Chaudhuri A THEORY OF TYPED COERCIONS AND ITS APPLICATIONS Nikhil Swamy, Michael Hicks and Gavin Bierman A UNIVERSE OF BINDING AND COMPUTATION Daniel Licata and Robert Harper ATTRIBUTE GRAMMARS FLY FIRST-CLASS: HOW TO DO ASPECT ORIENTED PROGRAMMING IN HASKELL Marcos Viera, S. Doaitse Swierstra and Wouter S. Swierstra AUTOMATICALLY RESTFUL WEB APPLICATIONS OR, MARKING MODULAR SERIALIZABLE CONTINUATIONS Jay McCarthy BEAUTIFUL DIFFERENTIATION Conal Elliott BIORTHOGONALITY, STEP-INDEXING AND COMPILER CORRECTNESS Nick Benton and Chung-Kil Hur CAUSAL COMMUTATIVE ARROWS AND THEIR OPTIMIZATION Hai Liu, Eric Cheng and Paul Hudak COMPLETE AND DECIDABLE TYPE INFERENCE FOR GADTS Tom Schrijvers, Simon Peyton Jones, Martin Sulzmann and Dimitrios Vytiniotis CONTROL-FLOW ANALYSIS OF FUNCTION CALLS AND RETURNS BY ABSTRACT INTERPRETATION Jan Midtgaard and Thomas P. Jensen EDUCATIONAL PEARL: FUN FOR FRESHMEN KIDS Matthias Felleisen, Robert Bruce Findler, Matthew Flatt and Shriram Krishnamurthi EFFECTIVE INTERACTIVE PROOFS FOR HIGHER-ORDER IMPERATIVE PROGRAMS Adam Chlipala, Gregory Malecha, Greg Morrisett, Avraham Shinnar and Ryan Wisnesky EXPERIENCE REPORT: EMBEDDED, PARALLEL COMPUTER-VISION WITH A FUNCTIONAL DSL Ryan Newton and Teresa Ko EXPERIENCE REPORT: HASKELL IN THE REALWORLD Curt Sampson EXPERIENCE REPORT: OCAML FOR AN INDUSTRIAL-STRENGTH STATIC ANALYSIS FRAMEWORK Pascal Cuoq and Julien Signoles EXPERIENCE REPORT: OCSIGEN, A WEB PROGRAMMING FRAMEWORK Vincent Balat, Jérôme Vouillon and Boris Yakobowski EXPERIENCE REPORT: SEL4 -- FORMALLY VERIFYING A HIGH-PERFORMANCE MICROKERNEL Gerwin Klein, Philip Derrin and Kevin Elphinstone FINDING RACE CONDITIONS IN ERLANG WITH QUICKCHECK AND PULSE Koen Claessen, Michal Palka, Nicholas Smallbone, John Hughes, Hans Svensson, Thomas Arts and Ulf Wiger FREE THEOREMS INVOLVING TYPE CONSTRUCTOR CLASSES Janis Voigtlaender GENERIC PROGRAMMING WITH FIXED POINTS FOR MUTUALLY RECURSIVE DATATYPES Alexey Rodriguez, Stefan Holdermans, Andres Löh and Johan Jeuring IDENTIFYING QUERY INCOMPATIBILITIES WITH EVOLVING XML SCHEMAS Pierre Geneves, Nabil Layaida and Vincent Quint IMPLEMENTING FIRST-CLASS POLYMORPHIC DELIMITED CONTINUATIONS BY A TYPE-DIRECTED SELECTIVE CPS-TRANSFORM Tiark Rompf, Ingo Maier and Martin Odersky LA TOUR D'HANOï Ralf Hinze NON-PARAMETRIC PARAMETRICITY Georg Neis, Derek Dreyer and Andreas Rossberg OXENSTORED: AN EFFICIENT HIERARCHICAL AND TRANSACTIONAL DATABASE USING FUNCTIONAL PROGRAMMING WITH REFERENCE CELL COMPARISONS Thomas Gazagnaire and Vincent Hanquez PARALLEL CONCURRENT ML John Reppy, Claudio Russo and Yingqi Xiao PARTIAL MEMOIZATION OF CONCURRENCY AND COMMUNICATION Suresh Jagannathan, KC Sivaramakrishnan and Lukasz Ziarek PURELY FUNCTIONAL LAZY NON-DETERMINISTIC PROGRAMMING Sebastian Fischer, Oleg Kiselyov and Chung-chieh Shan RUNTIME SUPPORT FOR MULTICORE HASKELL Simon Marlow, Simon Peyton Jones and Satnam Singh SAFE FUNCTIONAL REACTIVE PROGRAMMING THROUGH DEPENDENT TYPES Neil Sculthorpe and Henrik Nilsson SCRIBBLE: CLOSING THE BOOK ON AD HOC DOCUMENTATION TOOLS Matthew Flatt, Eli Barzilay and Robert Bruce Findler USING OBJECTIVE CAML TO DEVELOP SAFETY-CRITICAL EMBEDDED TOOL IN A CERTIFICATION FRAMEWORK Bruno Pagano, Olivier Andrieu, Thomas Moniot, Benjamin Canou, Emmanuel Chailloux, Philippe Wang, Pascal Manoury and Jean-Louis Colaco

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#haskell.pt IRC channel
by Marco Túlio Gontijo e Silva 15 May '09

15 May '09

Hello, I'd like to invite all Portuguese speakers haskellers to join #haskell.pt in irc.freenode.net. I added it to the list in http://www.haskell.org/haskellwiki/IRC_channel . Greetings. -- marcot http://marcot.iaaeee.org/

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Pretty printing a tree
by José Romildo Malaquias 15 May '09

15 May '09

Hello. I would like to pretty print a tree in a way that its structure is easily perceived. For instance, consider the declarations: data Node a = Node a [Node a] type Tree a = [ Node a ] t = [ Node "a" [ Node "b" [] , Node "c" [ Node "c1" [] , Node "c2" [] ] , Node "d" [ Node "d1" [ Node "d1a" [] ] , Node "d2" [] ] ] ] Then the resulting of pretty printing the given tree would be something like the following: a | +-------------+ | | | b c d | | +---+ +---+ | | | | c1 c2 d1 d2 | d1a There is the module Text.PrettyPrint.HughesPJ, but it lacks examples on how to use the pretty print combinators, and it is not well docomented. I would like to see solutions for this problem, or clues on how to solve it. Regards, José Romildo

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looking for suggestion on pattern matching problem
by Daryoush Mehrtash 14 May '09

14 May '09

I am trying to analyze a list of items (say integers) for longest matches on patterns and their location on the list. One catch is that pattern may be defined in terms of other patterns. Example of patterns would be the any sequence of increasing numbers, or sequence of increasing numbers followed by upto 5 zeros then followed by any odd digits. I don't know much about the actual patterns, but would like to be able to define EDSL for composing the patterns and an execution environment to actually find the patterns. I like to find out various ways I can structure the problem and its trade offs. I appreciate any books, articles, suggestions, papers, etc on this type of problems. Thanks, Daryoush

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