February 2005 - Haskell

Midlands Graduate School
by N Ghani 21 Feb '05

21 Feb '05

Dear Functional Programmers On 11-15 April, at the University of Birmingham, the Midlands Graduate School (a consortium of theoretical CS researchers at Birmingham, Nottingham, Leicester and Warwick) will be holding a spring school. It is aimed at first-year PhD students, but is open to other participants as well. http://www.cs.bham.ac.uk/~pbl/mgs/ The core courses will be Category theory, Graham Hutton Typed lambda-calculus, Paul Levy Denotational semantics, Achim Jung Students can select any combination of the following optional courses that fits the schedule. Programming stream Quantum programming, Thorsten Altenkirch Epigram, Conor McBride Functional reactive programming, Henrik Nilsson Logic and model-checking stream Modal logic, Natasha Alechina Game semantics for software verification, Dan Ghica Verifying security protocols, Mark Ryan Semantics stream Operational domain theory and topology, Martin Escardo Abstract Stone duality, Paul Taylor Game semantics for software verification, Dan Ghica And all that for just £40. University accommodation (£25 per night) can also be booked. Too much? Funding is available from EPSRC (UK) and APPSEM (EU), see http://www.cs.bham.ac.uk/~pbl/mgs/ for more details, and for a registration form. See you there Paul P.S. Students will also be able to attend a Workshop on Logic and Contro l on 16 April, for an additional fee. Details yet to be finalized.

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[announce] Fedora Haskell mailing list
by Jens Petersen 21 Feb '05

21 Feb '05

The Fedora Haskell project now has a mailing list which is kindly hosted on haskell.org. :) If you wish to subscribe for announcements and discussion of packaging Haskell projects for Fedora, please go to <http://haskell.org/mailman/listinfo/fedora-haskell>. More information about the project is available on <http://haskell.org/fedora> Cheers, Jens

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ICLP 2005: Call for Papers
by ICLP 2005 21 Feb '05

21 Feb '05

---------------------------------------- Apologies if you receive multiple copies ________________________________________ Call for Papers ------------------------------------------------------------ Twenty first International Conference on Logic Programming ICLP'05 2-5 October, 2005 Sitges (Barcelona) Spain Co-located with the International Conference on Principles and Practice of Constraint Programming (CP'05) ------------------------------------------------------------ http://www.iiia.csic.es/iclp2005/ The Conference -------------- The 21st International Conference on Logic Programming will be held near Barcelona (Spain) from October 2nd to October 5th, 2005. ICLP'05 will be colocated with the International Conference on Principles and Practice of Constraint Programming (CP'05). Conference scope ---------------- Since the first conference held in Marseilles in 1982, ICLP has been the premier international conference for presenting research in logic programming. Contributions (papers and posters) are sought in all areas of logic programming including but not restricted to: Theory Implementation Semantic Foundations Compilation Formalisms Memory Management Nonmonotonic Reasoning Virtual Machines Knowledge Representation Parallelism Environments Alternative Paradigms Program Analysis Constraint Logic Programming Program Transformation Abductive Logic Programming Validation and Verification Inductive Logic Programming Debugging, Profiling Answer Set Programming Language Issues Applications Concurrency Semantic Web Objects Software Engineering Coordination Web Tools Mobility Internet Agents Higher Order Artificial Intelligence Types Deductive Databases Modes Natural Language Programming Techniques Specific attention will be given to work providing novel integrations of these different areas, and to new applications of logic programming in general. Contributions on applications will be assessed with an emphasis on their impact and synergy with other areas, as opposed to technical maturity. Applications of logic programming to the Semantic Web are especially encouraged. The technical program will include several invited talks and advanced tutorials, in addition to the presentations of the accepted papers and posters. A special session on industrial applications of logic programming is also planned and several workshops will be held in parallel with the conference. For the first time, a doctoral student consortium will be organized as part of ICLP. Papers ------- Papers must describe original, previously unpublished research, and must not be simultaneously submitted for publication elsewhere. They must be written in English and not exceed 15 pages in Springer LNCS format. The authors are encouraged, although not obliged, to submit their papers already in Springer LNCS format. General information about the Springer LNCS series and the LNCS authors' instructions are available at the Springer LNCS/LNAI home page (http://www.springer.de/comp/lncs/index.html) Papers should express their contribution clearly, both in general and technical terms. It is essential to identify what was accomplished, describe its significance, and explain how the paper compares with and advances previous work. Authors should make every effort to make the technical content understandable to a broad audience. The primary means of submission will be electronic, in pdf format. If electronic submission is not possible, five hard copies should be sent to one of the program co-chairs. More information on the submission procedure will be available at http://www.utdallas.edu/ICLP05 Industrial Papers ----------------- A special session on industrial applications of logic programming is also planned during the conference. Papers accepted in this session will describe innovative applications of logic programming to industrial problems. The application's innovativeness and industrial impact will be the main criteria used for judging the paper. Papers accepted for this session will be published in the proceedings as shorter, (up to) 10 pages papers. Posters ------- Posters provide a forum for presenting work in an informal and interactive setting. They are ideal for discussing current work not yet ready for publication, for PhD thesis summaries and research project overviews. Accepted posters will also get a 10 minute slot for presentation during the conference. Extended abstract (2 pages) of each accepted poster will be published in the proceedings. Posters must be submitted electronically. More information on the submission procedure will be available at http://www.utdallas.edu/ICLP05 Doctoral Student Consortium --------------------------- The Doctoral Consortium will provide an opportunity for students pursuing their doctoral thesis in logic programming and related areas to explore their research interests under the guidance of a panel of distinguished experts in the field. The Doctoral Consortium will also offer invited speakers and discussion groups. The Consortium will allow participants to interact with established researchers and with other students, through presentations, question-answer sessions, panel discussions, and invited presentations. A separate call-for-participation will be issued for the doctoral consortium. About 6 to 8 students will be selected for the consortium. Selected students will also present their research in the poster session. The abstract of the poster will be published in the conference proceedings. Financial support for selected students may be available. Publication ----------- The proceedings of the conference will be published by Springer-Verlag in the LNCS series. The proceedings will include the accepted papers and the abstracts of accepted posters. Sponsoring and prizes --------------------- The conference is sponsored by the Association for Logic Programming. The ALP has funds to assist financially disadvantaged participants. The ALP is planning to sponsor two prizes for ICLP'05: for the best technical paper and for the best application paper. Important dates --------------- POSTERS PAPERS Abstract submission deadline: 30 April Submission deadline: 1 June 6 May Notification of authors: 1 July 24 June Camera-ready copy due: 15 July 15 July Organization ------------ Conference Co-Chairs: Pedro Meseguer (IIIA-CSIC, Spain) Javier Larrosa (Technical University of Catalonia, Spain) Program Co-Chairs: Maurizio Gabbrielli (University of Bologna, Italy) Gopal Gupta (University of Texas at Dallas, USA) Workshop Chair: Hai-Feng Guo (University of Nebraska at Omaha, USA) Doctoral Consortium Chair: Enrico Pontelli (New Mexico State University, USA) Publicity Chair: Felip Manya (IIIA-CSIC, Spain) Program Committee: Roberto Bagnara University of Parma, Italy Maurice Bruynooghe KU Leuven, Belgium Giorgio Delzanno University of Genova, Italy Stefan Decker Digital Enterprise Research Institute, Ireland Thom Fruehwirth University of Ulm, Germany Maurizio Gabbrielli University of Bologna, Italy (Program Co-Chair) Gopal Gupta University of Texas at Dallas, USA (Program Co-Chair) Patricia Hill University of Leeds, UK Joxan Jaffar University of Singapore, Singapore Bharat Jayaraman SUNY Buffalo, USA Javier Larrosa Technical University of Catalonia, Spain (Conference Co-Chair) Michael Leuschel University of Southampton, UK Massimo Marchiori University of Venice, Italy and W3C, MIT, USA Pedro Meseguer IIIA-CSIC, Spain (Conference Co-Chair) Juan J. Moreno Navarro Technical University of Madrid, Spain Gopalan Nadathur University of Minnesota, USA Illka Niemela Helsinki U. of Tech. Finland Catuscia Palamidessi INRIA, France Enrico Pontelli New Mexico State Univeristy, USA I.V. Ramakrishnan SUNY Stony Brook, USA Vitor Santos Costa Federal U. of Rio de Janeiro, Brazil Harald Sondergaard University of Melbourne, Australia Peter Stuckey University of Melbourne, Australia Frank Valencia University of Uppsala, Sweden Contact addresses ----------------- Conference Chairs: Pedro Meseguer Javier Larrosa IIIA-CSIC Dep. LSI, UPC Campus UAB Jordi Girona 1-3 08193 Bellaterra, Spain 08034 Barcelona, Spain Program Co-chairs: iclp05-chairs(a)cs.unibo.it Maurizio Gabbrielli Gopal Gupta Department of Computer Science Department of Computer Sciences MS EC31 University of Bologna The University of Texas at Dallas Mura A. Zamboni 7 2601 N. Floyd Rd 40127 Bologna, Italy Richardson, TX 78050, USA

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Job Advert
by N Ghani 20 Feb '05

20 Feb '05

EPSRC Funded Postdoctoral Fellowship Applications are invited for a research position available to work with Dr Neil Ghani and Dr Thorsten Altenkirch in the project THEORY AND APPLICATIONS OF CONTAINERS (EPSRC EP/C511964/1). The aim of this project is to develop both the theoretical foundations of containers and apply the results to other problems in Computer Science. The position is available from May 1 2005 and the appointment is for three years. Applicants should have a PhD in Computer Science or a related subject and a research record on developing and applying the theoretical foundations of computer science. Experience in category theory, functional programming and type theory are all desirable. Closing Date 15 March 2005 Contact: Dr Neil Ghani (ng13(a)mcs.le.ac.uk) and Dr Thorsten Altenkirch (txa(a)cs.nott.ac.uk)

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Snapshots of Haskell software (update)
by Sven Panne 20 Feb '05

20 Feb '05

I've uploaded fresh bleeding edge binary snapshots of Alex, Haddock and Happy for Win32 and x86 Linux to http://aedion.de/haskell/ The corresponding sources are available there, too. Hugs currently has a few build problems, but a new snapshot of it will be available there as well soon. Feedback is, as always, appreciated... Have fun, S.

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[ANNOUNCE] Non-ASCII Charset Support patch for Text.Regex
by shelarcy 19 Feb '05

19 Feb '05

Hello. Sakai Masahiro made a patch for GHC Text.Regex. Because Text.Regex doesn't support Non-ASII Charset well. He uses Onigurma what Regex C Library support Non-ASCII Charset well and GNU Regex Library replacement (this is usesd under Ruby version higher 1.9.X), replace for current Text.Regex's C library. Here is patch http://www.tom.sfc.keio.ac.jp/~sakai/d/?date=20050209#p01 and here is Onigurma's WebSite. http://www.geocities.jp/kosako3/oniguruma/ If you add this patch for GHC-6.2.2 sourcecode , autoconf, and ./configure with --enable-oniguruma option, then you can use Text.Regex with Oniguruma. -- shelarcy <shelarcy capella.freemail.ne.jp> http://page.freett.com/shelarcy/

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class assosiated types, via GADTs.
by John Meacham 19 Feb '05

19 Feb '05

I believe there is a realationship between GADTs and class assosiated types which hints at a much simpler implementation of class assosiated types (CATs) and possibly a lessoning of the constraints mentioned in the paper. Assuming you have already implemented GADTs the translation is straightforward, which is why I think it might be relevant to ghc developers. An example is worth a thousand words so here it is: Take the example from the paper: > class MapKey k where > data Map k v > lookup :: k -> Map k v -> Maybe v > empty :: Map k v > > instance MapKey Int where > data Map k v = MapInt (IntMap v) > lookup k (MapInt m) = Data.IntMap.lookup k m > empty = MapInt Data.IntMap.empty > > instance MapKey () where > data Map k v = MapUnit (Maybe v) > lookup () (MapUnit x) = x > empty = MapUnit Nothing now here is the translation: > class MapKey k where > lookup :: k -> Map k v -> Maybe v > empty :: Map k v > > data MapKey k => Map k v where > MapUnit :: Maybe v -> Map () v > MapInt :: IntMap v -> Map Int v > > instance MapKey Int where > lookup k (MapInt m) = Data.IntMap.lookup k m > empty = MapInt Data.IntMap.empty > > instance MapKey () where > lookup () (MapUnit x) = x > empty = MapUnit Nothing The idea should be clear, each CAT data declaration is lifted to the top level. each instance declares a new constructor for said class with an explicit GADT type fixing the type which the instance is being declared for. I have not worked out any theory behind it, but it seems to work in manual translation testing and has a certain intuitiveness about it. One might wonder whether we are paying a price for turning Map into a multi-construtor type, but we are just moving an implicit branch on an unknown function in the dictonary into an explicit case. (which is a win in my books) Since a 'Map Int v' cannot come about except via the MapInt constructor, we are guarenteed that the pattern matching in the instance declarations cannot fail if the program typechecks. The only caveats I can think of to actually implementing this in ghc are separate compilation, the Map GADT must be marked somehow as 'open' since later instances might create new constructors for it. Hopefully this won't interfere with optimization too much. Perhaps some internally generated rules to turn lookup :: Int -> Map Int v -> Maybe v into lookupInt :: Int -> IntMap v -> Maybe v would suffice. (this transformation is valid because we know that if the type of Map is Map Int v then its constructor has to be MapInt, despite the 'open' nature of the Map datatype) Once a rule fires, we no longer have any reference to the open GADT so can optimize like normal. * The front end will still have to be modified to type CATs similarly to as described in the paper, if nothing else for sane user error messages. (however, I believe some of the GADT machinery may be reusable) After typechecking, the translation can be carried out even before (and independently of) the desugaring of typeclasses. * It might just not work with multiparameter type classes, I have not thought about it at all, but then again CATs obviate much of the need for multi-parameter type classes, so having them mutually exclusive (at first) doesn't seem like too much of a restriction. I may be completely wrong about this, or perhaps it is already well known. or perhaps it is what the paper actually says to do and I am just misreading it :) I thought I'd share because I have really wanted the class assosiated types in various situations and I wasn't sure if I'd have time (or knowledge) to explore this seriously too much further. John -- John Meacham - ⑆repetae.net⑆john⑈

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Re: class assosiated types, via GADTs or FDs
by oleg＠pobox.com 17 Feb '05

17 Feb '05

Manuel M T Chakravarty wrote: > The functional dependency encoding prevents you from ever making the > representation of your tries/maps (in the MapKey class example) > abstract. It does not only prevent you from declaring it as an abstract > data type, but it actually forces users of a library built in this way > to understand the representation types and manually encode them in their > application code. It seems that problem can be easily solved in Haskell with the existing tools. First of all, one has to mention partial signatures, which are possible in Haskell to some extent (sufficient in our case) http://pobox.com/~oleg/ftp/Haskell/types.html#partial-sigs But mainly, if we wish to hide some details of the representation, why not to use tools that are built for that, such as applicative functors? They are _easily_ implementable in Haskell, arguably idiomatic, and free from the above drawbacks. The type system itself takes care to properly hide the representation. The following messages describe the realization of (generative and applicative and recursive) functors in great detail: http://www.haskell.org/pipermail/haskell/2004-August/014463.html http://www.haskell.org/pipermail/haskell/2004-September/014515.html Here's a simple example tailored to Manuel M T Chakravarty's sample code. First, the illustration of the problem: > {-# OPTIONS -fglasgow-exts #-} > {-# OPTIONS -fallow-undecidable-instances #-} > module MK where > > class MapKey k fm | k -> fm where > lookp :: k -> fm v -> Maybe v > empty :: k -> fm v > -- NB: The original signature of empty doesn't mention k, which > -- is already problematic, but you can fix this by > -- adding it as a dummy argument to fm. > > data BoolMap v = Integer > instance MapKey Bool BoolMap > > newtype AnyMap k v = AM [(k,v)] > instance MapKey Char (AnyMap Char) where > lookp k (AM m) = lookup k m > empty _ = AM [] > test1 = lookp True undefined Indeed, the type of lookp is *MK> :t lookp lookp :: forall k fm v. (MapKey k fm) => k -> fm v -> Maybe v If we want to specialize it for Bool keys, we indeed can't write lookpBool :: forall fm v. (MapKey Bool fm) => Bool -> fm v -> Maybe v but we perfectly well can write > lookpBool k m = lookp (k::Bool) m One can object that although we don't have to know how the Map of Bool keys is realized, we can actually see that, from the type of lookpBool. We have to hide that. But the type system already lets us do that. Let us look again at the type lookp :: forall k fm v. (MapKey k fm) => k -> fm v -> Maybe v The problem is the presence of `fm'. A few algebraic transformations on that expression give us forall k v. k -> (exists fm. (MapKey k fm) => fm v) -> Maybe v which is easily realizable in Haskell. > data Map' k v = forall fm. MapKey k fm => Map' (fm v) > > class MapKey' k where > lookp' :: k -> Map' k v -> Maybe v > lookp' k (Map' m) = lookp k m > empty' :: Map' k v One and only instance of MapKey' we will ever need: > instance MapKey k fm => MapKey' k where > empty' = Map' (empty (undefined::k)) First we note that the signature of empty' _does_ mention the type of keys in essential manner -- but does not leak the representation of the map. We also note that type of lookp': *MK> :t lookp' lookp' :: forall k v. (MapKey' k) => k -> Map' k v -> Maybe v Now, the representation of the map is perfectly hidden. We can now write: > test2 = let m = empty' in lookp' 'a' m > test3 = let m = empty' in lookp' True m No unneeded signatures -- and the ``library'' automatically adjusts the representation of maps based on the type of the key -- which seems to have been the main motivation for the associated types.

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Announcement: APPSEM-II Summer School, Sep 8-12
by Hans-Wolfgang Loidl 17 Feb '05

17 Feb '05

APPSEM II Summer School Frauenchiemsee, September 8-12, 2005 1st CALL FOR PARTICIPATION The IST-FET Summer School on Applied Semantics (APPSEM-II) will take place September 8-12, 2005 in Frauenchiemsee near Munich. We are proud to announce the following confirmed speakers: Andrew Pitts, Cambridge: Nominal Syntax and Semantics Philippa Gardner, London: Local Reasoning about Data Update Francois Pottier, Paris: A modern eye on ML type inference: old techniques and recent developments Gilles Barthe, Nice: Dependent Types in Programming Chris Hankin, London: Principles of Program Analysis The school is open to all interested graduated and (senior) undergraduate students as well as researchers. A limited number of student grants covering all fees, accommdation, and travel, are available. Neither participation nor grants are restricted to APPSEM sites. For details including deadlines please see the WWW page at http://www.appsem.org/summer_school.html

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MTCoord'05: Second call for papers
by Isabelle Linden 17 Feb '05

17 Feb '05

[ Our apologies for multiple copies. ] ====================================================================== Second Call for Papers 1st International Workshop on Methods and Tools for Coordinating Concurrent, Distributed and Mobile Systems (MTCoord 2005) April 23, 2005, Namur, Belgium Workshop affiliated to Coordination'2005, April 20 - 23 2005 ====================================================================== IMPORTANT DATES: o March 1, 2005: Abstract submission deadline. o March 8, 2005: Paper Submission deadline. o April 1, 2005: Notification of acceptance. o April 10, 2005: Final version. o April 23, 2005: Meeting Date. SCOPE Various classes of computational models, languages, and formalisms have emerged in the aim of providing high-level descriptions of concurrent, distributed, and mobile systems. Typical examples include so-called coordination languages and models (e.g. Gamma, Linda, Manifold, Reo, Klaim, Lime, ...), concurrent constraint languages (e.g. cc languages, Mozart, ...) and process algebras (e.g. CSP, CCS, pi-calculus, ...). These models are based on generative communication via a shared data space or on data communication through channels. In both cases, software components are typically conceived in isolation assuming that the required data will eventually be available. However, making a whole system out of these components and, in particular, ensuring that interactions occur properly is far from being obvious. The aim of the workshop is precisely to bring together researchers, working in different communities (coordination, constraints, process algebras), on methods and tools for the construction of concurrent, distributed and mobile systems. TOPICS OF INTEREST Topics of interest include but are not limited to o Model checking techniques, in particular parallel, distributed and probabilistic ones o Design of high-level specifications, eg based on first-order, modal and temporal logics o Techniques for requirements capture and analysis o Theorem proving based methodologies o Compositional and refinement-based methodologies o Debugging techniques o Abstract interpretation o Program analysis and transformation o Simulation and testing o Formal methods for security o Tools environments and architectures o Applications and case studies, in particular in web services and biology SUBMISSION GUIDELINES Papers describing original work are solicited as contributions to MTCoord 2005. Submitted papers should be limited to 6 000 words, preferrably formatted according to the Electronical Notes in Theoretical Computer Science. They should be submitted through the conference management system that will be available from the workshop web site http://www.info.fundp.ac.be/MTCoord/MTCoord05 PUBLICATION Selected work will be published in a volume of the Electronical Notes in Theoretical Computer Science. LOCATION The workshop will be held in Namur in April 23 2005. It is a satellite workshop of Coordination 2005. For venue and registration, see the Coordination'2005 web page at http://www.coordination2005.org WORKSHOP ORGANIZERS o Lubos Brim, Masaryk University Brno, Czech Republic o Isabelle Linden, University of Namur, Belgium PROGRAMME COMITTEE (provisional) o Ivana Cerna, Masaryk University Brno, Czech Republic o Rance Cleaveland, State University of New York at Stony Brook, USA o Giorgio Delzanno, University of Genova, Italy o Wan Fokkink, CWI, The Netherlands o Jean-Marie Jacquet, University of Namur, Belgium o Marta Kwiatkowska, University of Birmingham, United Kingdom o Angelika Mader, University of Twente, The Netherlands o Andreas Podelski, Max Planck Institute, Germany o Kaisa Sere, Abo Akademi University, Finland o Peter Van Roy, University of Louvain-la-Neuve, Belgium o Mirko Viroli, Alma Mater Studiorum Università di Bologna a Cesena, Italy

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