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The Monad.Reader - http://www.haskell.org/tmrwiki/IssueTwo
by Shae Matijs Erisson 03 May '05

03 May '05

For issue two, the subjects are Template Haskell, better module compatibility, exploring dark corners of GHC, domain specific languages, and the Foreign Function Interface. We've also switched to an experimental wikipublishing format, in hopes of removing the bottlenecks that showed up in the first issue, and encouraging more peer review. We'd like to hear your feedback! http://www.haskell.org/tmrwiki/IssueTwo -- It seems I've been living two lives. One life is a self-employed web developer In the other life, I'm shapr, functional programmer. | www.ScannedInAvian.com One of these lives has futures (and subcontinuations!)| --Shae Matijs Erisson

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Data.Array.ST, polymorphism, and escaping type variables
by Samuel J.J.Bronson 03 May '05

03 May '05

I was trying to implement quicksort using Data.Array.ST. I can't find a typing for qsortIndices in the following module: <file name="STUArraySort.hs"> {-# OPTIONS_GHC -fglasgow-exts #-} module STUArraySort where import Control.Monad.ST import Data.Array.IArray import Data.Array.MArray import Data.Array.ST import Data.Array.Unboxed mkIndices (arr) = (newListArray (bounds arr) (indices arr)) qsortIndices :: (Ord e, IArray a e, MArray (STUArray s) i (ST s)) => a i e -> UArray i i qsortIndices arr = runSTUArray $ do mkIndices arr </file> When I try to load this in GHCi, I get a nasty type error -- I even get this if I take out the type signature. I noticed a comment in Data.Array.ST that looks quite related: -- INTERESTING... this is the type we'd like to give to runSTUArray: -- -- runSTUArray :: (Ix i, IArray UArray e, -- forall s. MArray (STUArray s) e (ST s)) -- => (forall s . ST s (STUArray s i e)) -- -> UArray i e -- -- Note the quantified constraint. We dodged the problem by using -- unsafeFreezeSTUArray directly in the defn of runSTUArray above, but -- this essentially constrains us to a single unsafeFreeze for all STUArrays -- (in theory we might have a different one for certain element types). In a similar vain, I think that the signature I want would be: qsortIndices :: (Ord e, IArray a e, forall s. MArray (STUArray s) i (ST s)) => a i e -> UArray i i Unfortunately, this is not even syntactically valid... -- Thanks, Sam

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rekursive array problem
by Andreas Fuertig 03 May '05

03 May '05

Hi @ all! I have a big problem. i have a list of variables and now i need something like this fillArray ["a"] should be something like this: [[("a",True)],[("a",False)]] fillArray ["a","b"] [[("a",True),("b",True)],[("a",False),("b",True)],[("a",True),("b",False)], [("a",False),("b",False)]] and so on. i tried many things, and i dont know how to solve this. allthesame vars = [(alltrue [] vars)] ++ [(allfalse [] vars)] alltrue liste [] = liste alltrue liste (x:xs) = alltrue (liste ++ [(x,True)]) xs allfalse liste [] = liste allfalse liste (x:xs) = allfalse (liste ++ [(x,False)]) xs this works, but whats with the rest :) it would be very nice, if somebody could help me. thank you Andreas

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Haskell workshop 2005: second call for papers.
by Daan Leijen 01 May '05

01 May '05

[I apologize for cross-postings. Please forward to interested colleagues] 2005 Haskell Workshop Tallinn, Estonia, 30 September, 2005 http://www.cs.uu.nl/~daan/hw2005 Second Call for papers -- Important Dates --------------------------------------------------- Submission deadline : June 10 Acceptance notification: July 5 Final version due : July 19 Haskell workshop : September 30 -- The Haskell Workshop ---------------------------------------------- The Haskell Workshop 2005 is an ACM SIGPLAN sponsored workshop affiliated with the 2005 International Conference on Functional Programming (ICFP). Previous Haskell Workshops have been held in La Jolla (1995), Amsterdam (1997), Paris (1999), Montreal (2000), Firenze (2001), Pittsburgh (2002), Uppsala (2003), and Snowbird (2004). -- Scope ------------------------------------------------------------- The purpose of the Haskell Workshop is to discuss experience with Haskell, and future developments for the language. The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of Haskell. Topics of interest include, but are not limited to, the following: * Language Design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, in the form of a formal treatment of the semantics of the present language or future extensions, type systems, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management as well as foreign function and component interfaces; * Tools, in the form of profilers, tracers, debuggers, pre-processors, and so forth; * Applications, Practice, and Experience, with Haskell for scientific and symbolic computing, database, multimedia and Web applications, and so forth as well as general experience with Haskell in education and industry; * Functional Pearls, being elegant, instructive examples of using Haskell. Papers in the latter two categories need not necessarily report original research results; they may instead, for example, report practical experience that will be useful to others, re-usable programming idioms, or elegant new ways of approaching a problem. The key criterion for such a paper is that it makes a contribution from which other practitioners can benefit. It is not enough simply to describe a program! If there is sufficient demand, we will try to organise a time slot for system or tool demonstrations. If you are interested in demonstrating a Haskell related tool or application, please send a brief demo proposal to the program chair (daan(a)cs.uu.nl) -- Submissions ------------------------------------------------------- Authors should submit papers in postscript or portable document format (pdf), formatted for A4 paper, to Daan Leijen (daan(a)cs.uu.nl) The length should be restricted to 12 pages in standard ACM SIG proceedings format. In particular, LaTeX users should use the most recent sigplan proceedings style available from the Haskell workshop web-site. Furthermore, the "abbrv" style should be used for the bibliography. Accepted papers are published by the ACM and appear in the ACM digital library. Each paper should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. Authors should strive to make the technical content of their papers understandable to a broad audience. -- Program committee ------------------------------------------------- Martin Erwig Oregon State University John Hughes Chalmers University of Technology Mark Jones OGI School of Science and Engineering at OHSU Ralf Lämmel Microsoft Corp. Daan Leijen Universiteit Utrecht (Program Chair) Andres Löh Universiteit Utrecht Andrew Moran Galois Connections Inc. Simon Thompson University of Kent Malcolm Wallace University of York

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manipulating untyped lambda-calculus in Haskell
by Vivian McPhail 01 May '05

01 May '05

Hi, I am writing a NL parser in Haskell, relying on combinatorial grammar for the syntactic derivation. Each word has an associated syntax and semantics, the semantic term is a lambda expression loaded at run-time using hs-plugins. I : np : <semantic term> :: Sem m a love : s\np : <semantic term> :: Sem m a Predicates in english can have up to 5 arguments, and some of these arguments are functions, so the type of Sem m a is an enumeration of the types that we can build up from (STT m a) and (->). I started by enumerating this by hand: \begin{code} data Monad m => Sem m a = ZSem (SST m a) | USem (SST m a -> SST m a) | BSem (SST m a -> SST m a -> SST m a) | TSem (SST m a -> SST m a -> SST m a -> SST m a) | QSem (SST m a -> SST m a -> SST m a -> SST m a -> SST m a) | FSem (SST m a -> SST m a -> SST m a -> SST m a -> SST m a -> SST) -- | U1Sem ((SST m a -> SST m a) -> SST m a) | B1Sem ((SST m a -> SST m a) -> SST m a -> SST m a) | T1Sem ((SST m a -> SST m a) -> SST m a -> SST m a -> SST m a) \end{code} then what I need is a function to apply these: \begin{code} applySem :: Monad m => Sem m a -> Sem m a -> Sem m a applySem (USem a) (ZSem b) = ZSem $ a b applySem (BSem a) (ZSem b) = USem $ a b applySem (TSem a) (ZSem b) = BSem $ a b applySem (QSem a) (ZSem b) = TSem $ a b applySem (U1Sem a) (USem b) = ZSem # a b applySem (B1Sem a) (USem b) = USem $ a b applySem (T1Sem a) (USem b) = BSem $ a b applySem (T2Sem a) (ZSem b) = B1Sem $ a b applySem (B12Sem a) (USem b) = U1Sem $ a b applySem _ _ = error "application of Semantic functions" \end{code} My typing system ensures that only the correct functions will be applied to each other (the typing system manipulates lambda terms with an additional type (Stc Name (Sem m a)). A complete parse will reduce the lambda terms to closed terms containing only App and Stc, no Var or Lam. I can then use applySem to reduce the term to a single (Sem m a) type, which I can then run. What I have done thus far is enumerate by hand, but for full coverage for 5 argument predicates I need to list 5^5 data constructors and entries in the applySem function. For theoretically complete coverage I would need to enumerate all possible types constructed from (STT m a) and (->). It seems that I must be missing something? Is there a more elegant way of doing this? One can make the observation that the applySem function always applies a function of type (b -> a) to a function of type b to yield a function of type a. I suppose I could write a code generator (in haskell) that enumerates all possible derivations of (STT m a) and (->) but there would still be 5^5 data constructors. Thanks, Vivian McPhail PS Is there something I can do with the Typeable class of hs-plugins?

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MonadPlus
by Ashley Yakeley 01 May '05

01 May '05

I've added a bit more to <http://haskell.org/hawiki/MonadPlus>. I highly recommend people read it before they start claiming in papers that such-and-such a type "may thus be an instance of MonadPlus". -- Ashley Yakeley, Seattle WA

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Reminder: PAT2005 Summer School
by jespera＠diku.dk 30 Apr '05

30 Apr '05

======== REMINDER of PAT2005 ======== Dates have changed: REGISTRATION is OPEN NOW Fee Waiver applications: 8. May Registration closes 20. May Summer School: Program analysis and transformation Organized by: Computer Science Department (DIKU), University of Copenhagen, Denmark Monday-Friday 6-10 June, 2005 Summer School homepage: http://www.diku.dk/PAT2005/ This summer school on Program analysis and transformation will span theory and practice in the field. The overall theme is semantics-based program manipulation, in which practically-motivated operations on programs are solidly based in the semantics of the underlying programming languages. Research profile of the Summer School's topics: This research field began with classical compiler optimisations. These were pragmatically successful and well-automated, but lacking in semantic foundations. This led to the long-pursued goal of truly semantics-based generation of compilers and of abstract machines to implement programming languages. Parallel academic developments included more powerful and interesting program transformations that were developed by hand, one at a time. Major progress has been made in all three areas: semantically well-founded compiler optimisations have been devised and well-automated; compilers and abstract machines can now be generated by semantics-based methods including partial evaluation; and there now exist more powerful, general and well-founded program transformations. The speakers at this Summer School represent the state of the art in this research field. Confirmed speakers and their topics are: Mooly Sagiv (Israel: Tel Aviv) Program analysis using Three-Valued Logic Olivier Danvy (Denmark: Aarhus) On one-step reduction, evaluation, and abstract machines Oege De Moor (UK: Oxford) Incremental execution of transformation specifications Nick Benton, Microsoft Research Cambridge Semantics of static analyses and program transformations Neil Jones (Denmark: DIKU, Copenhagen) Size-change termination analysis of first and higher-order programs Torben Mogensen (Denmark: DIKU, Copenhagen) Introduction to partial evaluation; Program semi-inversion Arne Glenstrup (Denmark: ITU, Copenhagen) Tool tutorial for the Scheme partial evaluators PGG and Similix John Gallagher (Denmark: Roskilde) Program analysis and specialisation using tree automata Robert Glueck (Denmark: DIKU, Copenhagen) Program inversion Kazuhiko Kakehi (Japan: MIST, Tokyo Uniiversity) Attribute grammars and program transformations Prerequisites: Students should have some familiarity with classical compiler optimisations. A basic knowledge of operational semantics of programming languages (eg Structural operational semantics, Natural semantics or Action semantics) would be helpful. Sponsors: The PAT Summer School is partly supported by FIRST Graduate School: http://first.dk/ APPSEM-II: http://www.tcs.informatik.uni-muenchen.de/~mhofmann/appsem2/ Microsoft Research: http://research.microsoft.com/aboutmsr/labs/ Danish Natural Science Research Agency: http://www.forsk.dk Web pages: PAT home page: http://www.diku.dk/PAT2005/ (with details on lecture topics, speaker profiles, timetable, etc.) DIKU guest page: http://www.diku.dk/diku/gaester/index.html (with details on local transport, maps, hotels, etc.) Registration: The registration fee is DKK 1100 = EURO 150. This includes lecture materials, lunches and coffees, and a Summer School dinner. A block of rooms will be reserved at a hotel in central Copenhagen -- specifically, the new Cab Inn. Attendees are expected to arrange and pay for their own travel and lodging. Registration will Open: 5. April, 2005 Close: 20. May, 2005. Fee waivers: There will be a limited number of grants covering part or all of the registration fee. Application materials are available at the course's web page at the beginning of the registration period. Local Organisation Committee: Neil Jones neil(a)diku.dk Andrzej Filinski andrzej(a)diku.dk Torben Mogensen torbenm(a)diku.dk Jesper Andersen jespera(a)diku.dk Karin Outzen karino(a)diku.dk

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[ANNOUNCEMENT]: TFP '05: First Call for Papers
by Kevin Hammond 30 Apr '05

30 Apr '05

[With apologies in advance for any duplication. Kevin] FIRST CALL FOR PAPERS TFP 2005 <http://www.tifp.org/tfp05>: Sixth Symposium on Trends in Functional Programming, September 23rd-24th 2005, Tallinn, Estonia (co-located with ICFP 2005 and GPCE 2005). The 2005 Symposium on Trends in Functional Programming (TFP '05) is an international forum for researchers with interests in all aspects of functional programming languages, focusing on providing a broad view of current and future trends in Functional Programming. Previous TFP symposia were held in Munich, Germany in 2004, in Scotland in 2002 and 2003, as successors to the successful series of Scottish Functional Programming Workshops. TFP <http://www.tifp.org/> aims to combine a lively environment for presenting the latest research results with a formal post-symposium refereeing process leading to the publication by Intellect of a high-profile volume containing a selection of the best papers presented at the symposium. A review of a previous TFP proceedings can be found in the July 2003 issue of the Journal of Functional Programming. BEST STUDENT PAPER AWARD TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. The TFP05 best student paper award (i.e. for the best paper with a student as first author) acknowledges more formally the special attention TFP has for students. The 2004 award was given to Ron van Kesteren for the paper entitled: "Proof Support for General Type Classes". In order to enhance the quality of student submissions, student papers will be given the option of a feedback on their submission to the symposium proceedings. This feedback is intended for authors who are less familiar with a formal publication process and will provide general qualitative feedback on the submission, but will not give a grade or ranking. SCOPE OF THE SYMPOSIUM The Symposium recognises that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five categories of paper. High-quality papers are solicited in any of these categories: RESEARCH PAPERS (leading-edge, previously unpublished research work) POSITION PAPERS (on what new trends should or should not be) PROJECT PAPERS (descriptions of recently started new projects) EVALUATION PAPERS (what lessons can be drawn from a finished project) OVERVIEW PAPERS (summarizing work with respect to a trendy subject) Papers must be original, and not submitted for simultaneous publication in any other forum. They may consider any aspect of functional programming: theoretical, implementation- oriented, or more experience-oriented. Also applications of functional programming techniques to other languages may be considered. Papers on the following subject areas are particularly welcome: o functional programming and security o functional programming and mobility o functional programming applied to global computing o functional languages for embedded systems o telecommunications applications in functional languages o functional GRIDs o validation and verification of functional programs o functional languages for reasoning about imperative/object-oriented programs o interoperability with imperative programming languages o dependently typed functional programming o any new emerging trend in the functional programming area If you are in doubt on whether your paper is within the scope of TFP, please contact the TFP05 program chair, Marko van Eekelen, marko(a)cs.ru.nl. PROCEEDINGS Acceptance to the symposium will be based upon extended abstracts of at least 6 and at most 10 pages. Accepted abstracts are to be completed to full papers for publication in the proceedings that will be available at the symposium in Tallinn. In addition, we intend to continue the TFP tradition of publishing a high-quality subset of contributions in the Intellect series on Trends in Functional Programming. Revised papers will be refereed after the symposium to the normal standards and a subset of the best papers over all categories will be selected for publication by Intellect. This implies (among other things) that: * the paper is written in English. * the paper is well written. * the topic of the paper should be stated clearly. * the submission should clearly indicate to which paper category it belongs: a research, position, project, evaluation or overview paper; it should also indicate whether the paper is a student paper (i.e. first author a student). * for research papers, the approach to solving the problem should be outlined clearly and a detailed discussion of the solution must be given. * the work is properly compared with relevant related work. * there is an abstract, introduction and conclusion. * for research papers, the conclusion should summarise the problem, the solution, and how the work solves the problem. * papers for the symposium proceedings must adhere to the formatting instructions using the tfp.cls style, as will be provided on the TFP05 site; papers must not exceed 16 pages (papers in some categories may comprise considerably less pages). * papers submitted for publication by Intellect must follow formatting and any other instructions provided by the Program Chair. Papers will be judged on their contribution to the research area, with different criteria applying to different categories of paper, as appropriate. SIGNIFICANT DATES Submission of extended abstracts: Friday 8th July 2005 Notification of acceptance: Friday 22th July 2005 Early registration deadline: Friday 29th July 2005 Submission of full papers: Friday 2nd September 2005 Symposium at Tallinn, Estonia: Friday 23rd-Saturday 24th Sept. 2005 Feedback to student papers: Friday 21st October 2005 (provisional) Submission for formal proceedings: Friday 16th December 2005 (provisional) Notification of acceptance: Friday 10th February 2006 (provisional) Camera-ready version: Friday 10th March 2006 (provisional) ORGANISATION Symposium Chair: Kevin Hammond (University of St. Andrews) Program Chair: Marko van Eekelen (Radboud University Nijmegen, NL) Local Organisation: Tarmo Uustalu (Institute of Cybernetics, Tallinn) Treasurer: Greg Michaelson (Heriot-Watt University, Edinburgh) PROGRAM COMMITTEE: Andrew Butterfield, Trinity College Dublin Therese Hardin, Université Paris VI Kevin Hammond, St Andrews University John Hughes, Chalmers University Graham Hutton, University of Nottingham Hans-Wolfgang Loidl, Ludwig-Maximilians-University Munich Rita Loogen, Philipps-University Marburg Greg Michaelson, Heriot-Watt University Edinburgh John O'Donnell, University of Glasgow Ricardo Peña, Universidad Complutense de Madrid Claus Reinke, Canterbury, UK Sven Bodo Scholz, University of Hertfordshire Doaitse Swierstra, Utrecht University Phil Trinder, Heriot-Watt University Edinburgh Tarmo Uustalu, Institute of Cybernetics, Tallinn (and some other still unconfirmed members) SPONSORS We are actively looking for additional TFP sponsors, who may help to subsidise attendance by research students, for example. If you or your organization might be willing to sponsor TFP, or if you know someone who might be willing to do so, please do not hesitate to contact the Symposium chair: Kevin Hammond. Your students will be grateful!

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CFP: International Summer School On Applied Semantics 2005
by Hans-Wolfgang Loidl 29 Apr '05

29 Apr '05

2nd CALL for PARTICIPATION International Summer School On Applied Semantics 2005 Frauenchiemsee, Germany, 8-12 September 2005 http://lionel.tcs.ifi.lmu.de/SummerSchool05/ The International Summer School On Applied Semantics 2005, part of the APPSEM II initiative, will be held on the island of Frauenchiemsee, an island in Lake Chiemsee near Munich, from September 8 to 12, 2005. The summer school provides an opportunity to attend courses on various topics in the area of applied semantics given by leading members of the community. The summer school is organised by the APPSEM II Working Group, and the University of Munich. Immediately after the summer school a workshop on applied semantics will be held at the same location. The summer school is addressed to postgraduate students, researchers and industrials who want to learn about recent developments in programming language research, both in semantic theory and in implementation. LECTURERS Andrew Pitts: Nominal Syntax and Semantics Philippa Gardner: Local Reasoning about Data Update Francois Pottier: A modern eye on ML type inference: old techniques and recent developments Gilles Barthe: Type Checking Dependent Types Chris Hankin: Principles of Program Analysis REGISTRATION AND DATES To register for the Summer School, down-load and fill-in the application form from the Summer School's web page and fax it to: +49 89 2180 9338. The registration fee for the Summer School is 180 Euro, covering attendance of all courses, lecture notes, and meals. Additionally, several options of accomodation, ranging from 25 to 50 Euros per night, are available from the main site of the venue. Deadline for Registration: 1 July 2005 Notification for Grants: 15 July 2005 Summer School: 8-12 September 2005 A limited number of student grants is available. To apply for a grant, fill-in the corresponding section in the above form, too. LOCATION The International Summer School On Applied Semantics 2005 will be held in Frauenchiemsee, an island in Lake Chiemsee, on the border between Germany and Austria, about 100kms in the south east of the Munich Airport or about 70 km in the west of Salzburg Airport. ORGANISING COMMITTEE Prof Martin Hofmann Dr Hans-Wolfgang Loidl Sigrid Roden Konstantin Kutzkow CONTACT Sigrid Roden, Ludwig-Maximilians-Universitaet Muenchen, Institut fuer Informatik, Theoretische Informatik, Oettingenstrasse 67 D 80538 Muenchen GERMANY Fax: +49 89 2180 9337 Tel: +49 89 2180 9338

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REMINDER: Contributions to the HC&A Report (May 2005 edition)
by Andres Loeh 28 Apr '05

28 Apr '05

Dear Haskellers, the deadline for the May 2005 edition of the Haskell Communities and Activities Report is only a few days away -- but this is still enough time to make sure that the report contains a section on *your* project, on the interesting stuff that you've been doing; using or affecting Haskell in some way. Many projects that have been included in former reports have not yet updated their entries. Please have a look at http://haskell.org/communities/topics.html and at the November 2004 edition for reference. * Has your project been listed in previous Reports, but is not yet updated? Please write a short update! * Are you no longer working on a project that was included in the Report? Write up what you are working on instead, and tell me if someone else has picked up the project. * Is some project you have heard about not included in any previous Report? Please let me know ... There is still time to write a completely new entry, on a new compiler, tool, library, company, user group, idea, ... -- as long as there is a connection to the Haskell language, there is a place for it in the Report! Submissions are due by next Tuesday, that is Tuesday, 03 May 2005. Please mail your entries to <hcar at haskell dot org>, in plain text or pseudo-(La)TeX format. More information can be found in the original Call for Contributions at http://www.haskell.org/pipermail/haskell/2005-April/015688.html I look forward to receiving your contributions. Thanks a lot, Andres (current editor) -- Haskell Communities and Activities Report (http://haskell.org/communities) 05/2005 edition submission deadline: 03 May 2005 <hcar(a)haskell.org>

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