November 2005 - Haskell

Can anyone help me with partition numbers?
by whoals (sent by Nabble.com) 28 Nov '05

28 Nov '05

A partition of a positive integer n is a representation of n as the sum of any number of positive integral parts. For example, there are 7 partitions of the number 5: 1+1+1+1+1, 1+1+1+2, 1+1+3, 1+2+2, 1+4, 2+3 and 5. Define a function parts which returns the list of distinct partitions of an integer n. For example, parts 4 = [[1,1,1,1],[1,1,2],[1,3],[2,2],[4]]. -- Sent from the Haskell - Haskell forum at Nabble.com: http://www.nabble.com/Can-anyone-help-me-with-partition-numbers--t612331.ht…

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Re: ANNOUNCE: Frag: a First Person Shooting game
by Daniel �rstadius 27 Nov '05

27 Nov '05

I cannot get Frag to compile. Running "ghc --make -O2 -fglasgow-exts main.hs" gives ... Compiling Quaternion ( ./Quaternion.hs, ./Quaternion.o ) Compiling ReadImage ( ./ReadImage.hs, ./ReadImage.o ) ./ReadImage.hs:60: Type constructor or class not in scope: `PixelData' ./ReadImage.hs:68: Data constructor not in scope: `PixelData' I am using ghc 6.2.2. I have tried adding "-package GLUT" to the command line, but still the same output. Daniel __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

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Coordination 2006: Second call for papers
by Jean-Marie JACQUET 27 Nov '05

27 Nov '05

[ Our apologies for multiple copies. ] ====================================================================== Second Call for Papers COORDINATION 2006 8th International Conference on Coordination Models and Languages http://www.cs.unibo.it/discotec06/Coordination06 as part of DisCoTec'06 - Distributed Computing Techniques co-located with DAIS'06 & FMOODS'06 http://www.cs.unibo.it/discotec06 Bologna, Italy 14-16 June 2006 ====================================================================== IMPORTANT DATES * Submission of abstract: 10 January 2006 * Submission of papers: 17 January 2006 * Notification of acceptance: 7 March 2006 * Final version: 28 March 2006 * Conference: 14-16 June 2006 ====================================================================== CONFERENCE GOALS Modern information systems rely increasingly on combining concurrent, distributed, mobile, reconfigurable and heterogenous components. New models, architectures, languages, verification techniques are necessary to cope with the complexity induced by the demands of today's software development. Coordination languages have emerged as a successful approach, in that they provide abstractions that cleanly separate behavior from communication, therefore increasing modularity, simplifying reasoning, and ultimately enhancing software development. Building on the success of the previous editions, this conference provides a well-established forum for the growing community of researchers interested in models, languages, architectures, and implementation techniques for coordination. PREVIOUS EDITIONS The previous editions of COORDINATION took place in Cesena (Italy), Berlin (Germany), Amsterdam (Netherlands), Limassol (Cyprus), York (UK), Pisa (Italy) and Namur (Belgium). More details are available at http://www.coordination2005.org. TOPICS OF INTEREST They include but are not limited to: * Theoretical models and foundations for coordination: component composition, concurrency, mobility, dynamic aspects of coordination, emergent behavior. * Specification, refinement, and analysis of software architectures: patterns and styles, verification of functional and non-functional properties. * Coordination, architectural, and interface definition languages: implementation, interoperability, heterogeneity. * Multiagent systems and coordination: models, languages, infrastructures. * Dynamic software architectures: mobile code and agents, configuration, reconfiguration, self-organization. * Coordination and modern distributed computing: Web services, peer-to-peer networks, grid computing, context-awareness, ubiquitous computing. * Programming languages, middleware, tools, and environments for the development of coordinated applications * Industrial relevance of coordination and software architectures: programming in the large, domain-specific software architectures and coordination models, case studies. * Interdisciplinary aspects of coordination PROCEEDINGS Proceedings of previous editions of this conference were published by Springer, in the Lecture Notes in Computer Science (LNCS) series and are available as LNCS volumes 1061, 1282, 1594, 1906, 2315, 2949 and 3454. The intention is to continue this series. SUBMISSION INSTRUCTIONS Authors are invited to submit full papers electronically in PostScript or PDF using a two-phase online submission process. Registration of the paper information and abstract (max. 250 words) must be completed before 10 January 2006. Submission of the full paper is due no later than 17 January 2006. Further instructions on the submission procedure will be published at http://www.cs.unibo.it/discotec06/Coordination06. Submissions must be formatted according to the LNCS guidelines (see http://www.springer.de/comp/lncs/authors.html) and must not exceed 15 pages in length. Papers that are not in the requested format or significantly exceed the mandated length may be rejected without going through the review phase. Submissions should explicitly state their contribution and their relevance to the theme of the conference. Other criteria for selection will be originality, significance, correctness, and clarity. Simultaneous or similar submissions to other conferences or journals are not allowed. CONFERENCE LOCATION The conference will be hosted by the Department of Computer Science of the University of Bologna. PROGRAM COMMITTEE Co-Chairs Paolo Ciancarini University of Bologna, Italy Herbert Wiklicky Imperial College London, UK Members Farhad Arbab CWI Amsterdam, The Netherlands Antonio Brogi University of Pisa, Italy Wolfgang Emmerich University College London, UK Frank de Boer CWI & Utrecht University, The Netherlands Jean-Marie Jacquet University of Namur, Belgium Josst Kok Leiden University, The Netherlands Toby Lehman IBM Almaden, US D.C. Marinescu University of Central Florida, US Ronaldo Menezes Florida Institute of Technology, US Andrea Omicini University of Bologna, Italy Paolo Petta OeFAI, Austria Gian Pietro Picco Politecnico di Milano, Italy Ernesto Pimentel University of Malaga, Spain Rosario Pugliese University of Florence, Italy Gruia Catalin Roman Washington University, USA Robert Tolksdorf FU Berlin, Germany Emilio Tuosto University of Leicester, UK Carlos Varela Rensselaer Polytechnic Institute, US Alan Wood University of York, UK

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Call For Papers: ISMM 2006 (International Symposium on Memory Management)
by Erez Petrank 27 Nov '05

27 Nov '05

***************************************************************************** Call For Papers The 2006 International Symposium on Memory Management (ISMM'06) Co-located with PLDI 2006 Ottawa, Canada June 10-11 2006 http://www.cs.technion.ac.il/~erez/ismm06 ***************************************************************************** IMPORTANT DATES: Submission: January 23, 2006, 11PM PST Notification: March 6, 2006 Camera-ready: Monday, April 3, 2006 ISMM is a forum for research in management of dynamically allocated memory. ISMM solicits full-length papers on all areas of memory management. Survey papers that present an aspect of memory management with a new clarity and insight are also welcome. Papers are solicited on, but not limited to, these topics, - Explicit storage allocation and de-allocation - Garbage collection algorithms and implementations - Compiler analyses to aid memory management - Interaction with languages, operating systems, and hardware, especially the memory system - Memory system interaction with programming languages, operating systems, and hardware. The ISMM 2006 paper reviewing process adds two features new to ISMM: double blind reviewing, and an opportunity for rebuttal; see the ISMM webpage for more details. Full submissions should be at most 12 pages excluding bibliography and well-marked appendices but including all figures and tables, using at least 11-point font and reasonable margins for US Letter paper. Papers that violate these guidelines will be rejected by the program chair. Program committee members are not required to read appendices, and so a paper should be intelligible without them. Submitted papers must be in English and formatted to print on US Letter (8.5 x 11 inches) paper. Submissions must contain an abstract and postal and electronic mailing addresses for at least one author. Instructions for on-line submission of papers will become available on the ISMM webpage at http://www.cs.technion.ac.il/~erez/ismm06. Submissions will be read by the program committee and designated reviewers and judged on scientific merit, innovation, readability, and relevance. Papers previously published or already being reviewed by another conference are not eligible; if a closely related paper has been submitted to a journal, the authors must notify the program chair. The proceedings will be published by ACM. Authors should read the ACM Author Guidelines and related information. Authors of accepted papers must guarantee that their paper will be presented at the conference. For additional information please feel free to contact the Program Chair, Eliot Moss (moss(a)cs.umass.edu) General Chair: Erez Petrank (Technion, Israel) Program Chair: J. Eliot B. Moss (Univ. of Mass. at Amherst) Program Committee: Vikram Adve (Univ. of Illinois at Urbana-Champaign) Richard Jones (Univ. of Kent) Hillel Kolodner (IBM Haifa Research Lab) Chandra Krintz (Univ. of California at Santa Barbara) Kathryn S McKinley (Univ. of Texas at Austin) Greg Morrisett (Harvard University) Ravi Rajwar (Intel) Yannis Smaragdakis (Georgia Tech) Guy Steele (Sun Microsystems)

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ANNOUNCE: Frag: a First Person Shooting game
by Mun Hon Cheong 26 Nov '05

26 Nov '05

Frag is a 3D First Person Shooting game. Features: *Yampa, a domain-specific embedded language for the programming of hybrid systems that using the concepts of Functional Reactive Programming (FRP) was used to program the game entities. *The Quake 3 BSP level format, Q3Map2, and the MD3 format for models and animations are used in this game. *Sven Panne's OpenGL binding, HOpenGL is used to render graphics. Requirements: HOpenGL which is provided with GHC OpenGL drivers that support the vertex array and multitexture OpenGL extensions Darcs: darcs get http://www.cse.unsw.edu.au/~pls/repos/frag Thanks goes to Don Stewart, this project would not have become public if not for him. Enjoy, Mun

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RE: [Haskell] Can anyone help me with partition numbers?
by E. Zuurbier (Erik) 25 Nov '05

25 Nov '05

Doaitse, For generate 4 this gives a.o. three equivalent solutions: [1,1,2], [1,2,1] and [2,1,1]. I guess the ultimate idea would be to prune permutations. Regards Erik Zuurbier Onderwerp: Re: [Haskell] Can anyone help me with partition numbers? Or (since we started to do someone's homework anyway) generate 0 = [[]] generate n = [x:rest | x <- [1..n], rest <- generate (n-x)] Doaitse Swierstra On 2005 nov 25, at 10:29, Tomasz Zielonka wrote: > On Thu, Nov 24, 2005 at 05:52:23PM +0100, Jan van Eijck wrote: >> Like so: >> >> generatePs :: (Int,[Int]) -> [[Int]] >> generatePs (n,[]) = [take n (repeat 1)] >> generatePs (n,(x:xs)) = >> (take n (repeat 1) ++ (x:xs)) : generatePs (pack (x-1) ((n >> +x),xs)) >> where >> pack :: Int -> (Int,[Int]) ->(Int,[Int]) >> pack 1 (m,xs) = (m,xs) >> pack k (m,xs) = if k > m then pack (k-1) (m,xs) >> else pack k (m-k,k:xs) >> >> parts :: Int -> [[Int]] >> parts n | n < 1 = error "part: argument <= 0" >> | n == 1 = [[1]] >> | otherwise = generatePs (0,[n]) > > How about a shorter version? > > part :: Integer -> [[Integer]] > part = gen 1 > where > gen m 0 = [[]] > gen m n = [ x:xs | x <- [m..n], xs <- gen x (n - x) ] > > Best regards > Tomasz > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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Broken monad laws
by Iavor Diatchki 24 Nov '05

24 Nov '05

Hello, I just noticed that the GHC/Hugs "standard" libraries have acquired a list monad transformer, which is broken, because it does not satisfy the associativity law when applied to non-commutative monads. I am not referring to some corner-case strictness problem, but rather a fairly well known result. The associativity law is important, because without it the 'do' notation can be very confusing. Bellow is an example, for people not familiar with the porblem. -Iavor import Control.Monad.List say :: String -> ListT IO () say x = lift (putStr x) one_two, ex1,ex2 :: ListT IO () one_two = say "1 " `mplus` say "2 " ex1 = do one_two say "3 " say "4 " ex2 = do do one_two say "3 " say "4 " main = runListT ex1 >> putStrLn " or " >> runListT ex2

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Lazy state monads
by Yitzchak Gale 23 Nov '05

23 Nov '05

(Moved from the libraries list to the haskell list.) I wrote: > > createItems :: RandomGen g => State g [Item] > > createItems = > > liftM catMaybes $ runListT $ > > flip evalStateT initialState $ runMaybeT $ > > do > > item <- liftRandom $ repeatM randomItem > > updateState item > > needMoreItems >>= guard > > return item > > where > > liftRandom = lift . lift . lift Udo Stenzel wrote: > ...but this is probably broken anyway. After > (repeatM randomItem) presumably the state (the > RandomGen) is _|_, but the type of createItems > would suggest it is still usable. No, it works. MaybeT tells ListT when to stop its iteration. After that, the RandomGen can be used again elsewhere. > I wouldn't do that. Other than that it's a bit > hard to see what you're trying to accomplish > here. Lazy monads are an important programming paradigm in practice. Laziness helps to completely decouple the various ingredients of the algorithm from each other. This helps in debugging, and in dividing tasks among different development teams. The monadic approach helps makes refactoring easy (a common complaint against Haskell). For example, it would be trivial to add exception handling, or logging. The algorithm is clearly specified as an iteration of a series of steps, the way most people would naturally think of it. Yet the calculation is completely pure. So a compiler is not required to follow the steps literally. It can split the calculation across different threads, processors, http connections, etc., if it is smart enough. This is the way industrial software development should be done. It is clearly far better than imperative OO. Regards, Yitz

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Haskell Weekly News: November 22, 2005
by John Goerzen 22 Nov '05

22 Nov '05

Haskell Weekly News: November 22, 2005 Greetings, and thanks for reading the 16th issue of HWN, a weekly newsletter for the Haskell community. Each Tuesday, new editions will be posted (as text) to [1]the Haskell mailing list and (as HTML) to [2]The Haskell Sequence. 1. http://www.haskell.org/mailman/listinfo/haskell 2. http://sequence.complete.org/ New Releases There are several exciting releases to report this week. * hmp3. Donald Bruce Stewart [3]announced hmp3, an ncurses-based music player written in Haskell. 3. http://article.gmane.org/gmane.comp.lang.haskell.general/12637 * Frag. Mon Hon Cheong [4]announced Frag, a first-person shooter written in Haskell using HOpenGL. Several comments were posted offering thanks and seeking more information. [5]Screenshots are also available. 4. http://thread.gmane.org/gmane.comp.lang.haskell.general/12628 5. http://haskell.org/hawiki/Frag * Haskell Communities & Activities Report. The November 2005 editition of this report is now [6]available. 6. http://article.gmane.org/gmane.comp.lang.haskell.general/12624 * Haskell Server Pages 0.4.0. The latest release of HASP is now [7]available, featuring a new bytecode generator and less of a need for many other add-on packages. 7. http://article.gmane.org/gmane.comp.lang.haskell.general/12617 * Blobs diagram editor. The first release of Blobs was [8]announced this week. It is based on earlier work that has been shown at some Haskell conferences. 8. http://article.gmane.org/gmane.comp.lang.haskell.general/12603 Requests for Participation Take 10 list. Kenneth Hoste [9]posted a request for user contributions regarding a top 10 list of Haskell libraries. 9. http://article.gmane.org/gmane.comp.lang.haskell.general/12639 Discussion Updating Haskell. It's been a busy week for these discussions. There have been threads on [10]records (~ 200 messages) and [11]GHC. Unfortunately your HWN editor hasn't had time to read these monster threads, so have at it! 10. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/9201 11. http://thread.gmane.org/gmane.comp.lang.haskell.general/12592 About Haskell Weekly News Want to continue reading HWN? Please help us create new editions of this newsletter. Please see the [12]contributing information, or send stories to hwn -at- complete -dot- org. There is also a Darcs repository available. 12. http://sequence.complete.org/hwn-contrib

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take 10 [1..] article series: Libraries ( please contribute ! )
by Kenneth Hoste 22 Nov '05

22 Nov '05

As was already announced, I'll try to provide an article for each upcoming TMR [1] issue, regarding some subject in the world of Haskell. My intention is to write a short piece on some item which fits the monthly subject. The first topic for the series of 'take 10 [1..]' articles is Libraries, and will be published in the next TMR issue (December). I'll choose a top 10 (without ordering, this is no popularity contest), and try and summarize what the library is meant for, who is maintaining it, why you should use it, ... I'd like to ask this mailing list to make a contribution: which Haskell library is your favorite, which ones do you _really_ need for your work with Haskell, which ones do you like. Please feel free to reply one or more suggestions, or adjust the wiki [2]. [1] http://haskell.org/tmrwiki [2] http://haskell.org/tmrwiki/TopTenHaskell_25Libraries boegel -- Statistics are like a bikini. What they reveal is suggestive, but what they conceal is vital (Aaron Levenstein) Kenneth Hoste ELIS - Ghent University http://elis.ugent.be/~kehoste

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