September 2004 - Haskell

Overloading show
by Stephan Zaubzer 10 Sep '04

10 Sep '04

Hello Everyone! I am relatively new to Haskell (actually it's my second day) and I have the following problem: If I define a new datatype, for example a Binary tree, how can i use the show function to put an instance of my datatype into a String representation. I have seen in different Tutorials that there is a way for overloading the show function for my own type, and I tried out, what was presented in the tutorials, but it didn't work. Does somebody know, how to manage this? Here my attempts: data Entry a = EmptyEntry | MakeEntry a a showEntry :: (Show a) => Entry a -> String showEntry EmptyEntry = "Empty" showEntry MakeEntry a b = show a ++ ": " ++ show b what am I doing wrong? I have seen this way on some tutorials. btw: I am working with Hugs98 thank you in advance for your help Stephan

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Re: [Haskell] Overloading show
by J.Garrett.Morris＠Dartmouth.EDU 10 Sep '04

10 Sep '04

--- Stephan Zaubzer wrote: data Entry a = EmptyEntry | MakeEntry a a showEntry :: (Show a) => Entry a -> String showEntry EmptyEntry = "Empty" showEntry MakeEntry a b = show a ++ ": " ++ show b --- end of quote --- That's a good start. All you need to do now is make Entry an instance of the Show class: > instance (Show a) => Show (Entry a) > where show = showEntry Also, you have a small syntax error in showEntry - you probably want: > showEntry (MakeEntry a b) = show a ++ ": " ++ show b Finally, using ShowS is generally better for this kind of thing. <http://www.haskell.org/tutorial/stdclasses.html> describes the disadvantages of using repeated appends and the advantages of ShowS. Hope that helps! /gXm

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lazy printing
by Serge D. Mechveliani 10 Sep '04

10 Sep '04

Dear Haskellers, Can you tell me how to force Haskell to output the results in a `lazy' way? Consider, for example, the program main = putStr (concat ["\n min1 = ", show min1, "\n min2 = ", show min2, "\n" ] ) where min1 = minimum [1 .. 10 ] :: Integer min2 = minimum [1 .. (10^10)] :: Integer I do not know whether the effect is due to implementation. And I `make'-run the program under GHC-6.2.2-pre by commanding ghc -O --make Main ./a.out This prints min1 = 1 and hangs silently -- probably, because min2 takes long to compute. But why does not it print immediately min1 = 1 min2 = ? This is for the first time in my practice that a `lazy' printing is essential. The above example is contrived. The real example is a program that searches for the proof and accumulates a certain ptrace :: ProofTrace, type ProofTrace = [Step] The first steps are performed easily, and also they are informative. So, the user should see their results immediately -- when one applies (show ptrace). The whole proof may take long, the last steps in ptrace may be ready after a very long time. And Haskell just holds until the whole ptrace is ready, which is annoying. Copy, please, the answer to mechvel(a)botik.ru With kind regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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GPCE'04 - early registration deadline approaching
by Eelco Visser 10 Sep '04

10 Sep '04

CALL FOR PARTICIPATION ---------------------------------------------------------------------- Online Registration http://www.regmaster.com/oopsla2004.html early registration with reduced rates closes September 16 ---------------------------------------------------------------------- Third International Conference on Generative Programming and Component Engineering (GPCE'04) Vancouver, October 24-28, 2004 co-located with OOPSLA 2004 and ISMM 2004 http://gpce04.gpce.org ---------------------------------------------------------------------- Generative and component approaches have the potential to revolutionize software development in a similar way as automation and components revolutionized manufacturing. Generative Programming (developing programs that synthesize other programs), Component Engineering (raising the level of modularization and analysis in application design), and Domain-Specific Languages (elevating program specifications to compact domain-specific notations that are easier to write and maintain) are key technologies for automating program development. GPCE arose as a joint conference, merging the prior conference on Generative and Component-Based Software Engineering (GCSE) and the Workshop on Semantics, Applications, and Implementation of Program Generation (SAIG). The goal of GPCE is to provide a meeting place for researchers and practitioners interested in cutting edge approaches to software development. We aim to foster further cross-fertilization between the software engineering research community on the one hand, and the programming languages community on the other, in addition to supporting the original research goals of both the GCSE and the SAIG communities. We seek papers both in software engineering and in programming languages, and especially those that bridge the gap and are accessible to both communities at the same time. * Invited speakers * Keynote: Jack Greenfield on Software Factories * Peter Mosses on Modular Language Descriptions * Technical program * 25 papers * Aspect-orientation * Staged programming * Meta-programming * Model-driven approaches * Product lines * Domain-specific languages * Tutorials * Adaptive Object-Model Architecture: Dynamically Adapting to Changing Requirements * Multi-stage Programming in Meta-OCaml * Generative Software Development * Program Transformation Systems: Theory and Practice for Software Generation, Maintenance and Reengineering * Workshops * Software Transformation Systems Workshop * First MetaOCaml Workshop * Young Researchers Workshop * Workshop on Best Practices Model-Driven Software Development * Workshop on Managing Variabilities Consistently in Design and Code * Demonstrations * Implementation of DSLs using staged interpreters in MetaOCaml * MetaEdit+: Domain-Specific Modeling for Full Code Generation Demonstrated * Towards Domain-Driven Development: the SmartTools Software Factory * Xirc: Cross-Artifact Information Retrieval * C-SAW and GenAWeave: A Two-Level Aspect Weaving Toolsuite * The Concern Manipulation Environment * Program Transformations for Re-Engineering C++ Components

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"global variables" and code optimization
by "Holzmüller, Bernd" 10 Sep '04

10 Sep '04

Hi all, in a compiler project I am using "global variables" of the form: gNewLabelNr :: IORef Int gNewLabelNr = unsafePerformIO $ newIORef 1 getAndUpdateVar var f = unsafePerformIO $ do oldVal <- readIORef var writeIORef var (f oldVal) return oldVal makeBlockName = "Block_" ++ show (getAndUpdateVar gNewLabelNr (+1)) (I know I could use a Monad to avoid this kind of unsafe programming, but I don't (didn't) want to rewrite existing code.) The problem is, that with optimizations turned on (using ghc V6.2.1) the label number is calulated only once, so each call to makeBlockName yields the same value. I tried a) adding a dummy parameter to makeBlockName and b) specifying an INLINE pragma to both getAndUpdateVar and makeBlockName, but that doesn't help. What can I do to prevent optimization to optimize that calculation away? Thanks, Bernd

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[Haskell] CFP - PADL'2005 - Submission deadline *extended*, Sept. 17
by Manuel Hermenegildo 09 Sep '04

09 Sep '04

*** PAPER SUBMISSION DEADLINE EXTENDED: September 17th! *** FINAL CALL FOR PAPERS Seventh International Symposium on Practical Aspects of Declarative Languages 2005 (PADL 05) http://www.unm.edu/~herme/padl05/ Long Beach, California, USA January 10-11, 2005 Co-located with ACM POPL, January 12-14, 2005 Paper submission deadline: September 10th Declarative languages build on sound theoretical foundations to provide attractive frameworks for application development. These languages have been successfully applied to a wide array of different real-world situations, including database management, active networks, software engineering, decision support systems, or music composition. New developments in theory and implementation have opened up new application areas. At the same time, the application of declarative languages to novel problems raises numerous interesting research issues. Well-known questions include designing for scalability, language extensions for application deployment, and programming environments. Thus, applications often drive the progress in the theory and implementation of declarative systems, and benefit from this progress as well. PADL is a forum for researchers and practioners to present original work emphasizing novel applications and implementation techniques for all forms of declarative concepts, including, functional, logic, constraints, etc. Topics of interest include: * Innovative applications of declarative languages. * Declarative domain-specific languages and applications. * Practical applications of theoretical results. * New language developments and their impact on applications. * Evaluation of implementation techniques on practical applications. * Novel implementation techniques relevant to applications. * Novel uses of declarative languages in the classroom. * Practical experiences. PADL 05 welcomes new ideas and approaches pertaining to applications and implementation of declarative languages, and is not limited to the scope of the first six PADL symposia (past proceedings can be found in Springer Verlag LNCS, numbers 1551, 1753, 1990, 2257, 2562, and 3057). In this occasion PADL is co-located, as traditionally, with ACM POPL, which will be held immediately following PADL, January 12-14. IMPORTANT DATES Paper Submission: September 10, 2004 Notification: October 10, 2004 Camera-ready: November 10, 2004 Symposium: January 10-11, 2005 SUBMISSION GUIDELINES Authors should submit an electronic copy of the full paper (written in English) in Postscript (Level 2) or PDF. Submission should be completed using the electronic procedure available at the conference website. Papers must be no longer than 15 pages, written in 11-point font and with single spacing. Since the final proceedings will be published as Lecture Notes in Computer Science by Springer Verlag, authors are strongly encouraged to use the LNCS paper formatting guidelines for their submission. Each submission must include on its first page the paper title; authors and their affiliations; contact author's email and postal addresses, telephone and fax numbers, abstract, and three to four keywords. The keywords will be used to assist us in selecting appropriate reviewers for the paper. If electronic submission is impossible, please contact the program chairs for information on how to submit hard copies. PROGRAM COMMITTEE Kenichi Asai, Ochanomizu University, Japan Manuel Carro, T.U. Madrid, Spain Bart Demoen, K.U. Leuven, Belgium John Gallagher, Roskilde University, Denmark Hai-Feng Guo, University of Nebraska at Omaha, US Joxan Jaffar, National U. of Singapore, Singapore Alan Mycroft, Cambridge University, UK Gopalan Nadathur, U. of Minnesota, US Lee Naish, U. of Melbourne, Australia Simon Peyton-Jones, Microsoft Research, US John Reppy, University of Chicago, US Morten Rhiger, Roskilde University, Denmark Francesca Rossi, University of Padova, Italy Vitor Santos-Costa, U, Federal do Rio de Janeiro, Brazil Terrance Swift, S.U. of New York at Stony Brook, US David S. Warren, S.U. of New York at Stony Brook, US MOST PRACTICAL PAPER AWARD A cash prize of US$500 will be awarded to the submission that is judged by the program committee to be the best in terms of practicality, originality, and clarity of presentation. The program committee may choose not to make an award; or may make multiple awards, in which case the award money will be evenly divided. CONTACTS Please visit the conference web site: http://www.unm.edu/~herme/padl05/ for further information. For additional information about papers and submissions, please contact the Program Chairs: Manuel Hermenegildo (1,2) herme(a)unm.edu, or Daniel Cabeza (2) dcabeza(a)fi.upm.es 1 Departments of Computer Science and Electrical and Computer Engineering The University of New Mexico, Albuquerque, NM 87131, U.S.A. 2 Facultad de Informatica, Universidad Politecnica de Madrid 28660-Boadilla del Monte, Madrid, Spain For additional information about the conference please contact the General Chair: Gopal Gupta Department of Computer Science University at Texas at Dallas, Dallas, TX, U.S.A. gupta(a)utdallas.edu SPONSORED BY: ACM SIGPLAN (applied for), COMPULOG Americas (http://www.cs.nmsu.edu/~complog) The Association for Logic Programming (http://www.cs.kuleuven.ac.be/~dtai/projects/ALP/) -- ----------------------------------------------------------------------------- Manuel Hermenegildo | University of New Mexico, NM, USA Professor, P. of Asturias Chair | Office: ECE 219A Depts. of Computer Science and | Tel: +1 (505) 277 -9328/-3112 Electrical and Computer Engineering | http://www.unm.edu/~herme -----------------------------------------------------------------------------

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UNILOG'05
by COSTA LEITE Alexandre 08 Sep '04

08 Sep '04

Bonjour à tous Voici une annonce pour un grand congrès de logique qui sera organisé au printemps 2005 en Suisse. Il existe des possibilités d'obtenir des bourses pour participer à ce congrès à travers l'AUF (Agence Universitaire de la Francophonie), mais il faut se dépêcher car la limite pour déposer les dossiers est le 15 septembre prochain. Vous trouverez tous les détails sur le site du congrès. ****************************************************************************************************************************************************************** 1st World Congress and School on Universal Logic (UNILOG 2005) http://www.uni-log.org <http://www.uni-log.org/> Montreux - Switzerland, School : March 26-30 ; Congress : March 31 - April 3, 2005 This event will focus on: 1) Techniques that can be used for a general theory of logics (Labelled deductive systems, Kripke structures, Logical matrices, etc.) ; 2) Studies of classes of logics (Substructural logics, Non monotonic logics, Paraconsistent logics, etc.) 3) Scope of validity and domain of application of fundamental theorems of logic (Completeness, Deduction, Cut-elimination, etc.) 4) Philosophical considerations about the nature of logic and the universality of some logical laws or axioms The school is intended for advanced students and young researchers. There will be about 20 tutorials on many subjetcs: combination of logics, multiple conclusion logic, combinatory logic, logics and games, abstract model theory, logic as language vs. logic as calculus, category theory for logics, etc. Invited speakers of the congress will include A.Avron, D.Batens, J.Corcoran, M.Dunn, D.Gabbay, R.Jansana, A.Koslow, V.de Paiva, K.Segerberg. Contributed papers for the congress can be submitted before October 30, 2004. More information on the website: http://www.uni-log.org <http://www.uni-log.org/> ********************************************************************************************************************************************

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HTTP and Borwser modules maintainer
by Andre W B Furtado 07 Sep '04

07 Sep '04

Who is actually responsible for the Haskell "HTTP and Browser modules" (http://homepages.paradise.net.nz/warrickg/haskell/http/)? The e-mail indicated in the site (oinutter [at] hotmail.com) is returning... Thanks, -- Andre

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ICTAC04: Call for Participants
by Bernhard K. Aichernig 07 Sep '04

07 Sep '04

CALL FOR PARTICIPATION: ICTAC 2004 FIRST INTERNATIONAL COLLOQUIUM on THEORETICAL ASPECTS OF COMPUTING Guiyang, China 20 -- 24 September 2004 http://www.iist.unu.edu/ICTAC2004 The First International Colloquium on Theoretical Aspects of Computing (ICTAC04) will be held in Guiyang, the Guizhou Province China, during 20-24 September 2004. The technical programme of the colloqium includes workshop during which four outstanding invited talks, 36 presentations of high quality papers selected from 111 submissions from over 30 countries and regions. For the detailed programme, please visit http://www.iist.unu.edu/ICTAC2004/programme.html There will be six very good affiliated tutorials on 20 and 21 September 2004. YOU ONLY NEED TO PAY 100 YUAN (12 USD) to attend the tutorials. Information about the tutorial speakers and the abstracts of the tutorials are available at http://www.iist.unu.edu/ICTAC2004/tutorials.html For information about registration, hotel, visa application and social events, please visit the conference website. SCOPE AND OBJECTIVES The aim of the colloquium is to bring together practitioners and researchers from academia, industry and government to present research results, and exchange experience, ideas, and solutions for their problems in theoretical aspects of computing. We believe that this will help the developing countries to strengthen their research, teaching and development in computer science and engineering, to improve the links between developing countries and developed countries, and to establish collaboration in research and education. SCOPE AND TOPICS ICTAC 2004 calls for tutorials in the areas of theoretical aspects of computing including automata, languages, software engineering and formal methods and solicits research papers for the workshop related to, but not limited to, the following principal topics: * automata theory and formal languages * principle and semantics of programming languages * logics and their applications * software architectures and their description languages * formal techniques in MDA * software specification, refinement and verification * model checking and theorem proving *formal techniques in software testing * models of object and component system * coordination and feature interaction * integration of formal and engineering methods * service-oriented development * document-driven development * models of concurrency, security and mobility * theory of parallel, distributed and internet-based (Grid) computing *Boolean satisfiability (SAT) * real-time and embedded systems * type and category theory in computer science The proceedings will be available as a UNU-IIST technical report at the colloqium. It is planned to publish the accepted papers after the conference in revised full version in the Springer Lecture Notes in Computer Science series (http://www.springer.de/comp/lncs/index.html) INVITED SPEAKERS Jose Luiz Fiadeiro (University of Leicester, UK) Jifeng He (UNU-IIST, Macao) K. Rustan M. Leino (Microsoft Research, WA, USA) Huimin Lin (Institute of Software, CAS, Beijing, China) Program Committee Chairs Keijiro Araki (Kyushu University, Japan) Zhiming Liu (UNU-IIST, Macao SAR China) Publicity Chairs Bernhard Aichernig (UNU-IIST, Macao) Dan Li (Academy of Sciences, Guizhou, China) Finance Chair Danning Li (Academy of Sciences, Guizhou, China) Organization Chair Danning Li (Academy of Sciences, Guizhou, China) Advisory Committee Dines Bjorner (Denmark), Manfred Broy (Germany), Jose Luiz Fiadeiro (University of Leicester, UK), Jifeng He (UNU-IIST), Mathai Joseph (India), Shaoying Liu (Japan), Zhiming Liu (UNU-IIST), Jim Woodcock (UK) Program Committee Luis S. Barbosa (University of Minho, Portugal) Gabriel Baum (National University of La Plata, Argentina) Hubert Baumeister (LMU, Munich, Germany) Jonathan Bowen (London South Bank University, UK) Cristian S. Calude (University of Auckland, New Zealand) Ana Cavalcanti (University of Kent, UK) Wei Ngan Chin (NUS, Singapore) Jim Davies (Oxford University, UK) Henning Dierks (University of Oldenburg, Germany) Jin Song Dong (National University, Singapore) Wan Fokkink (CWI, the Netherlands) Michael R. Hansen (DTU, Lyngby, Denmark) James Harland (RMIT University, Melbourne, Australia) Jozef Hooman (Embedded Systems Institute, Eindhoven, the Netherlands) Guoxing Huang (ECNU, Shanghai, China) Purush Iyer (North Carolina State University, USA) Ryszard Janicki (McMaster University, Ontario, Canada,) Michael Johnson( Macquarie University, Sydney, Australia) Fabrice Kordon (University of Paris VI, France) Maciej Koutny (University of Newcastle upon Tyne, UK) Kung-Kiu Lau (Manchester University, UK) Antonia Lopes (University of Lisbon, Portugal) Jian Lu (Nanjing University, China) Andrea Maggiolo-Schettini (University of Pisa, Italy) Huaikou Miao (Shanghai University, China) Paniti Netinant (Bangkok University, Thailand) Paritosh Pandya (TIFR, Mumbai, India) Zongyan Qiu (Peking University, Beijing, China) Anders P. Ravn (Aalborg University, Denmark) Gianna Reggio (University of Genova, Italy) Riadh Robbana (LIP2/EPT, Tunisia) Augusto Sampaio (Federal Univ of Pernambuco, Recife, Brazil) Bernhard Schatz (TU Munchen, Germany) Irek Ulidowski (University of Leicester, UK) Miroslav Velev (Carnegie Mellon University, USA) Ji Wang (National Lab for Parallel and Distributed Processing, China) Wang Yi (Uppsala University, Swiden) Jian Zhang (Institute of Software, CAS, China) Mingyi Zhang (Academic of Sciences, Guizhou, China) Hongjun Zheng (Semantics Designs Inc, USA) -- Bernhard Aichernig, Research Fellow of UNU-IIST www.iist.unu.edu/~bka ---------------------------------------------------------------------- Go to China for SEFM 2004 www.iist.unu.edu/SEFM2004 and ICTAC 2004. www.iist.unu.edu/ICTAC2004 Plan to attend ASE 2004! www.ase-conference.org See you at FM 2005 www.csr.ncl.ac.uk/fm05

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Haskell recruitment?
by Jochen L. Leidner 06 Sep '04

06 Sep '04

Dear Haskell list subscribers, I'd be interested to learn what experiences you have had with recruiting Haskell developers (I shall post a summary of infos worth mentioning to the list if you e-mail me). Also, does anyone here have noteworthy experiences in the area of integration of code from Haskell programmers and non-Haskell programmers in a team (N.B. I'm talking about the software process in terms of teamwork best practices rather than the software-technical interoperability). Finally, would it be considered spam to post Haskell-realted job postings in this group? Thanks in advance. Regards, Jochen -- Jochen L Leidner, MA MPhil (CSTIT) <leidner(a)acm.org> PhD student <Jochen.Leidner(a)ed.ac.uk> University of Edinburgh <http://www.iccs.informatics.ed.ac.uk/~s0239229/> Try Nuggets, the new mobile phone search engine! <http://www.myNuggets.net/>

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