January 2006 - Haskell

RE: [Haskell] IO == ST RealWorld
by Simon Peyton-Jones 30 Jan '06

30 Jan '06

| Is there any reason why IO should not be defined as: | > type IO a = ST RealWorld a | in implementations that support ST? | | This way IORef/STRef and IOArray/STArray can be merged. I know under the | hood they already share code, but this way they can also share an interface. Indeed, this was the way we had it originally in GHC. It does seem like a good idea. We changed it for reasons that I know that we have forgotten, alas, because we tried to recall about a year ago. It's always possible that the original reasons for the change no longer apply. Perhaps someone can try it out? Simon

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TFP2006: Third Call for Papers
by Henrik Nilsson 30 Jan '06

30 Jan '06

Dear Colleague, Please find enclosed the third call for papers for Trends in Functional Programming (TFP) 2006. Please note that the abstract submission deadline is fast approaching: 17 Feb. Also note the co-location with Types 2006 and the Spring School on Datatype-Generic Programming. My apologies for duplicate copies. Best regards, /Henrik -- Henrik Nilsson School of Computer Science and Information Technology The University of Nottingham nhn(a)cs.nott.ac.uk This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. TFP 2006 Seventh Symposium on Trends in Functional Programming Nottingham, UK, 19 - 21 April, 2006 http://www.cs.nott.ac.uk/~nhn/TFP2006 Co-located with Types 2006 and Spring School on Datatype-Generic Programming CALL FOR PAPERS The Symposium on Trends in Functional Programming (TFP) 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. It aspires to be a lively environment for presenting the latest research results through acceptance by extended abstracts. A formal post-symposium refereeing process then selects the best papers presented at the symposium for publication in a high-profile volume. TFP 2006 is going to be held in Nottingham, UK, 19 - 21 April. Note that this is significantly earlier in the year than past TFPs that generally were held in August - September. TFP 2006 is co-located with Types 2006 (18 - 21 April). The TFP symposium is the successor to the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in Edinburgh, Scotland in 2003, in Munich, Germany in 2004, and in Tallinn, Estonia in 2005 (co-located with ICFP and GPCE). For further general information about TFP, see http://www.tifp.org/. 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: summarising 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 dependently typed functional programming o validation and verification of functional programs o debugging for functional languages o functional programming and security o functional programming and mobility o functional programming and formally motivated computing o functional languages for telecommunications applications o functional languages for embedded systems o functional programming applied to global computing o functional GRIDs o functional languages for reasoning about imperative/object- oriented programs o interoperability with imperative programming languages 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 TFP 2006 programme chair, Henrik Nilsson, nhn(a)cs.nott.ac.uk. BEST STUDENT PAPER AWARD TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. To acknowledge this, a prize for the best student paper is awarded each year. CO-LOCATION WITH TYPES 2006 AND DATATYPE-GENERIC PROGRAMMING 2006 TFP 2006 is co-located with Types 2006 (to be held 18 - 21 April). To take advantage of the synergies offered by these two complementary events, we will invite a number of joint keynote speakers, hold joint sessions on topics of mutual interest, such as dependently typed functional programming, and run common social events. The schedule will be arranged so that participants may freely move between parallel sessions of the two events. See http://www.cs.nott.ac.uk/types06/ for further details. TFP 2006 and Types 2006 are immediately followed by the Spring School on Datatype-Generic Programming 2006 (24 - 27 April), which should be of direct interest to many of the TFP and Types Participants. See http://www.cs.nott.ac.uk/ssdgp2006/ for further details. SUBMISSION AND LOCAL PROCEEDINGS Acceptance to the symposium is by extended abstracts of between 6 and 10 pages. Accepted abstracts are to be completed to full papers before the symposium for publication in the local symposium proceedings and on-line. Important dates: Deadline for abstract submission: 17 February, 2006 Notification of acceptance: 27 February, 2006 Registration deadline: 17 March, 2006 Camera-ready copy of full paper: 24 March, 2006 The submission must clearly indicate to which category it belongs: research, position, project, evaluation or overview paper. It should also indicate whether the main author or authors are research students. Abstracts and full papers must be written in English. Papers for the symposium proceedings must adhere to the formatting instructions provided on the TFP 2006 site. Papers must not exceed 16 pages; papers in some categories may comprise considerably fewer pages. The papers of the local proceedings will also be made available on-line under the following conditions, with which all authors are asked to agree: The documents distributed by this server have been provided by the contributing authors as a means to ensure timely dissemination of scholarly and technical work on a noncommercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, notwithstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder. See the TFP 2006 website for further instructions to authors and details on how to submit. POST SYMPOSIUM REFEREEING AND PUBLICATION In addition to the local symposium proceedings, we intend to continue the TFP tradition of publishing a high-quality subset of contributions in the Intellect series on Trends in Functional Programming (see http://www.intellectbooks.co.uk/series.php?series=1) All TFP authors will be invited to submit revised papers after the symposium. These will will be refereed to normal conference standards, and a subset of the best papers over all categories will be selected for publication. Papers will be judged on their contribution to the research area, with appropriate criteria applied to each category of paper. Papers submitted for publication by Intellect must follow formatting and any other instructions provided by the Programme Chair. For TFP 2005, in order to enhance the quality of student submissions, a process where student papers were given extra feedback was tried out. A similar process might be put in place for this TFP, contingent on the outcome of that trial. ORGANISATION Symposium Chair: Marko van Eekelen, Radboud University Nijmegen, NL Programme Chair: Henrik Nilsson, University of Nottingham, UK Treasurer: Greg Michaelson, Heriot-Watt University, UK Local Arrangements: Joel Wright, University of Nottingham, UK PROGRAMME COMMITTEE: o Kenichi Asai, Ochanomizu University o Gilles Barthes, INRIA, Sophia Antipolis o Olaf Chitil, University of Kent at Canterbury o Catherine Dubois, IIE, Evry o Marko van Eekelen, Radboud Universiteit Nijmegen o Jeremy Gibbons, Oxford University o Kevin Hammond, University of St Andrews o Zoltán Horváth, Eötvös Loránd University o Frank Huch, Christian-Albrechts-University of Kiel o Johan Jeuring, Universiteit Utrecht o Greg Michaelson, Heriot-Watt University o Henrik Nilsson, University of Nottingham o Ricardo Peña, Universidad Complutense de Madrid o Morten Rhiger, Roskilde University o Colin Runciman, University of York o Carsten Schürmann, IT University of Copenhagen o Zhong Shao, Yale University o Phil Trinder, Heriot-Watt University SPONSORS We are actively looking for additional TFP sponsors, who may help to subsidise attendance by research students, for example. If you or your organisation 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: Marko van Eekelen. Your students will be grateful!

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ACM PPDP'06 call for papers
by Simon Marlow 30 Jan '06

30 Jan '06

[ posting on behalf of Agostino Cortesi <cortesi(a)unive.it> ] ................................................................ PPDP 2006 Preliminary Call For Papers 8th ACM-SIGPLAN International Symposium on Principles and Practice of Declarative Programming Venice, Italy, July 10-12, 2006 http://www.dsi.unive.it/ppdp2006/ ................................................................ IMPORTANT DATES Submission 15 March 2006 Notification 22 April 2006 SCOPE: PPDP 2006 is a forum for the declarative programming communities, gathering researchers working on logic, constraint and functional programming, but also on other programming language paradigms like visual programming, executable specification languages, database languages, AI and knowledge representation languages for the "semantic web". MAIN TOPICS: Logic, Constraint, and Functional Programming; Database, AI and Knowledge Representation Languages; Visual Programming; Executable Specification for Languages; Applications of Declarative Programming; Methodologies Program Design and Development; Declarative Aspects of Object-Oriented Programming; Concurrent Extensions to Declarative Languages; Declarative Mobile Computing; Paradigm Integration; Proof Theoretic and Semantic Foundations; Type and Module Systems; Program Analysis and Verification; Program Transformation; Abstract Machines and Compilation; Programming Environments. PROCEEDINGS: Proceedings will be published by ACM Press. RELATED EVENTS: PPDP 2006 will be co-located with the 33rd International Colloquium on Automata, Languages and Programming (ICALP 2006), which will take place on July 9-16, 2006 (http://icalp06.dsi.unive.it) CONFERENCE CHAIR: Annalisa Bossi, U. Ca' Foscari di Venezia PROGRAM CHAIR: Michael Maher, National ICT Australia PROGRAM COMMITTEE: Nick Benton (Microsoft Research, UK) Annalisa Bossi (U. Ca' Foscari di Venezia, Italy) Manuel Chakravarty (U. NSW, Australia) Bart Demoen (K. U. Leuven, Belgium) Moreno Falaschi (U. Udine, Italy) Radha Jagadeesan (DePaul U., USA) Bharat Jayaraman (SUNY Buffalo, USA) Yukiyoshi Kameyama (U. Tsukuba, Japan) Andy King (U. Kent, UK) Francois Laburthe (Bouyges, France) David Sands (Chalmers U., Sweden) Christian Schulte (KTH, Sweden) Pascal Van Hentenryck (Brown U., USA) Roland Yap (NUS, Singapore) =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- prof. agostino cortesi tel. 0039 041 234.8450 dipartimento di informatica fax 0039 041 234.8419 universita' ca' foscari mail cortesi(a)dsi.unive.it via torino 155 url www.dsi.unive.it/~cortesi 30170 Venezia location: studio n.1

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AMAST 2006 Final Call for Papers (extended deadlines)
by Varmo Vene 29 Jan '06

29 Jan '06

NEWS: - Extended deadlines: * Submission of abstracts: 3 February 2006 * Submission of full papers: 10 February 2006 FINAL CALL FOR PAPERS 11th International Conference on Algebraic Methodology and Software Technology, AMAST '06 colocated with MPC '06 Kuressaare, Estonia, 5-8 July 2006 http://cs.ioc.ee/mpc-amast06/amast/ Background The major goal of the AMAST conferences is to promote research that may lead to the setting of software technology on a firm, mathematical basis. This goal is advanced by a large international cooperation with contributions from both academia and industry. The virtues of a software technology developed on a mathematical basis have been envisioned as being capable of providing software that is (a) correct, and the correctness can be proved mathematically, (b) safe, so that it can be used in the implementation of critical systems, (c) portable, i.e., independent of computing platforms and language generations, and (d) evolutionary, i.e., it is self-adaptable and evolves with the problem domain. The previous conferences were held in Iowa City, Iowa, USA (1989, 1991 and 2000), Twente, The Netherlands (1993), Montreal, Canada (1995), Munich, Germany (1996), Sydney, Australia (1997), Manaus, Amazonia, Brazil (1998), Reunion Island, France (2002) and Stirling, UK (2004, colocated with MPC' 04). The 2006 conference will be held at Kuressaare, Estonia, colocated with MPC '06. The conference series has become widely known for disseminating academic and industrial achievements within the broad AMAST areas of interest. Through these meetings AMAST has attracted an international following among researchers and practitioners interested in software technology, programming methodology and their algebraic and logical foundations. Important dates * Submission of abstracts: 3 February 2006 (extended) * Submission of full papers: 10 February 2006 (extended) * Notification of authors: 17 March 2006 * Camera-ready version: 14 April 2006 Topics Topics of interest include, but are not limited to, the following: * Software technology: systems software technology, application software technology, concurrent and reactive systems, formal methods in industrial software development, formal techniques for software requirements/design, evolutionary software/adaptive systems. * Programming methodology: logic programming, functional programming, object paradigms, constraint programming and concurrency, program verification and transformation, programming calculi, specification languages and tools, formal specification and development case studies. * Algebraic and logical foundations: logic, category theory, relation algebra, computational algebra, algebraic foundations for languages and systems, coinduction, theorem proving and logical frameworks for reasoning, logics of programs, algebra and coalgebra. * Systems and tools (for system demonstrations or ordinary papers): software development environments, support for correct software development, system support for reuse, tools for prototyping, component based software development tools, validation and verification, computer algebra systems, theorem proving systems. Submission and publication Two kinds of submissions are solicited for this conference: technical papers and system demonstrations. Papers may report academic or industrial progress, and papers which deal with both are especially well-regarded. Submission is in two stages. Abstracts (plain text) must be submitted by 3 February 2006 (extended). Full papers (pdf) adhering to the llncs style and not longer than 15 pages (6 pages for system demonstrations) must be submitted by 10 February 2006 (extended). The web-based submission system is open. Papers must report previously unpublished work and not be submitted concurrently to another conference with refereed proceedings. Accepted papers must be presented at the conference by one of the authors. All papers will be refereed by the programme committee, and will be judged based on their significance, technical merit, and relevance to the conference. The proceedings of AMAST '06 will be published in the Lecture Notes in Computer Science series of Springer-Verlag. Programme Committee Michael Johnson, Macquarie University (co-chair) Varmo Vene, University of Tartu (co-chair) Luís Barbosa, Universidade do Minho Gilles Barthe, INRIA Sophia-Antipolis Michel Bidoit, École Normale Supérieure de Cachan Gregor v. Bochmann, University of Ottawa Manfred Broy, Technische Universität München Cristian Calude, University of Auckland Christine Choppy, Université Paris Nord Arthur Fleck, University of Iowa Marcelo Frias, Universidad de Buenos Aires Nicolas Halbwachs, Université Grenoble I / CNRS Anne Haxthausen, Technical University of Denmark Antonia Lopes, Universidade de Lisboa Michael Mislove, Tulane University Peter Mosses, University of Wales Swansea Monica Nesi, Università degli Studi di L'Aquila Rocco De Nicola, Università degli Studi di Firenze Anton Nijholt, Universiteit Twente Dusko Pavlovic, Kestrel Institute Jaco van de Pol, CWI Charles Rattray, University of Stirling Teodor Rus, University of Iowa Giuseppe Scollo, Università degli Studi di Catania Carolyn Talcott, SRI International Andrzej Tarlecki, Warsaw University Ken Turner, University of Stirling Irek Ulidowski, University of Leicester Martin Wirsing, Ludwig-Maximilians-Universität München AMAST steering committee Egidio Astesiano, Universita degli Studi di Genova Robert Berwick, MIT Zohar Manna, Stanford University Michael Mislove, Tulane University Anton Nijholt, University of Twente Maurice Nivat, Universite Paris 7 Charles Rattray, University of Stirling Teodor Rus, University of Iowa Giuseppe Scollo, Universita degli Studi di Catania Michael Sintzoff, Universite Catholique de Louvain Jeannette Wing, Carnegie Mellon University Martin Wirsing, Ludwig-Maximilians-Universitaet Muenchen Michael Johnson, Macquarie University (chair) Venue Kuressaare (pop. 16000) is the main town on Saaremaa, the second-largest island of the Baltic Sea. Kuressaare is a charming seaside resort on the shores of the Gulf of Riga highly popular with Estonians as well as visitors to Estonia. The scientific sessions of MPC/AMAST 2006 will take place at Saaremaa Spa Hotel Meri, one among the several new spa hotels in the town. The social events will involve a number of sites, including the 14th-century episcopal castle. Accommodation will be at Saaremaa Spa Hotels Meri and Ruutli. To get to Kuressaare and away, one must pass through Tallinn (pop. 402000), Estonia's capital city. Tallinn is famous for its picturesque medieval Old Town, inscribed on UNESCO's World Heritage List. Local organizers MPC/AMAST 2006 is organized by Institute of Cybernetics, a research institute of Tallinn Univ. of Technology. The local organizers are Tarmo Uustalu (chair), Monika Perkmann, Juhan Ernits, Ando Saabas, Olha Shkaravska, Kristi Uustalu. Contact email addresses: mike(at)ics.mq.edu.au, varmo(at)cs.ut.ee.

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MPC 2006 Final Call for Papers (extended deadlines)
by Tarmo Uustalu 28 Jan '06

28 Jan '06

NEWS: - Extended deadlines: * Submission of abstracts: 3 February 2006 * Submission of full papers: 10 February 2006 FINAL CALL FOR PAPERS 8th International Conference on Mathematics of Program Construction MPC '06 Kuressaare, Estonia, 3-5 July 2006 http://cs.ioc.ee/mpc-amast06/mpc/ colocated with AMAST '06 Background The biennial MPC conferences aim to promote the development of mathematical principles and techniques that are demonstrably useful and usable in the process of constructing computer programs. Topics of interest range from algorithmics to support for program construction in programming languages and systems. The previous conferences were held in Twente, The Netherlands (1989), Oxford, UK (1992), Kloster Irsee, Germany (1995), Marstrand, Sweden (1998), Ponte de Lima, Portugal (2000), Dagstuhl, Germany (2002) and Stirling, UK (2004, colocated with AMAST '04). The 2006 conference will be held at Kuressaare, Estonia, colocated with AMAST '06. Invited speakers Robin Cockett, University of Calgary Olivier Danvy, Aarhus Universitet Oege de Moor, University of Oxford Important dates * Submission of abstracts: 3 February 2006 (extended) * Submission of full papers: 10 February 2006 (extended) * Notification of authors: 17 March 2006 * Camera-ready version: 14 April 2006 Topics Papers are solicited on mathematical methods and tools put to use in program construction. Topics of interest range from algorithmics to support for program construction in programming languages and systems. Some typical areas are type systems, program analysis and transformation, programming language semantics, program logics. Theoretical contributions are welcome provided their relevance for program construction is clear. Reports on applications are welcome provided their mathematical basis is evident. Submission and publication Submission is in two stages. Abstracts (plain text) must be submitted by 3 February 2006 (extended). Full papers (pdf) adhering to the llncs style must be submitted by 10 February 2006 (extended). There is no official page limit, but authors should strive for brevity. The web-based submission system is open. Papers must report previously unpublished work and not be submitted concurrently to another conference with refereed proceedings. PC members may submit. Accepted papers must be presented at the conference by one of the authors. The proceedings of MPC '06 will be published in the Lecture Notes in Computer Science series of Springer-Verlag. After the conference, the authors of the best papers will be invited to submit revised versions to a special issue of the Science of Computer Programming journal of Elsevier. Programme committee Tarmo Uustalu, Institute of Cybernetics, Tallinn (chair) Roland Backhouse, University of Nottingham Eerke Boiten, University of Kent Venanzio Capretta, University of Ottawa Sharon Curtis, Oxford Brookes University Jules Desharnais, Université de Laval Jeremy Gibbons, University of Oxford Lindsay Groves, Victoria University of Wellington Ian Hayes, University of Queensland William Harrison, University of Missouri Johan Jeuring, Universiteit Utrecht Dexter Kozen, Cornell University Christian Lengauer, Universität Passau Lambert Meertens, Kestrel Institute Bernhard Möller, Universität Augsburg Shin-Cheng Mu, University of Tokyo José Oliveira, Universidade do Minho Alberto Pardo, Universidad de la República Ross Paterson, City University London Ingrid Rewitzky, University of of Stellenbosch Varmo Vene, University of Tartu Satellite workshops Two workshops will be held in conjunction with MPC 2006 as satellites on 2 July 2006: 5th International Workshop on Constructive Methods for Parallel Programming, CMPP 2006 Workshop on Mathematically Structured Functional Programming, MSFP 2006 Venue Kuressaare (pop. 16000) is the main town on Saaremaa, the second-largest island of the Baltic Sea. Kuressaare is a charming seaside resort on the shores of the Gulf of Riga highly popular with Estonians as well as visitors to Estonia. The scientific sessions of MPC/AMAST 2006 will take place at Saaremaa Spa Hotel Meri, one among the several new spa hotels in the town. The social events will involve a number of sites, including the 14th-century episcopal castle. Accommodation will be at Saaremaa Spa Hotels Meri and Rüütli. To get to Kuressaare and away, one must pass through Tallinn (pop. 402000), Estonia's capital city. Tallinn is famous for its picturesque medieval Old Town, inscribed on UNESCO's World Heritage List. Local organizers MPC/AMAST 2006 is organized by Institute of Cybernetics, a research institute of Tallinn University of Technology. The local organizers are Tarmo Uustalu (chair), Monika Perkmann, Juhan Ernits, Ando Saabas, Olha Shkaravska, Kristi Uustalu. Contact email address: mpc06(at)cs.ioc.ee.

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page names on the new Haskell wiki
by Wolfgang Jeltsch 28 Jan '06

28 Jan '06

Hello, the names of the pages of the new MediaWiki-driven Haskell wiki are often rather directory names than "article titles" as they are on Wikipedia. For example, the page "Books and tutorials about Haskell" isn't named "Books and tutorials about Haskell" or "Books and tutorials" but just "Books". Another example is the GHC documentation page which is named "GHC/Documentation". Here the slash is used to express a hierarchy as it's done in UNIX path names, for example. But Wikipedia uses the slash just where it is used normally. For example, the term "I/O" contains a slash and the Wikipedia article about I/O is named "I/O". I propose that we stick to the Wikipedia convention and choose page names which are a short description of the page's topic in normal (English) language. Remember, that the page name is not only part of the page's URL but also displayed as a title on the page and in the window's title bar. What do you think? Best wishes, Wolfgang

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Scripting language: is Haskell a good choice?
by Jules Jacobs 27 Jan '06

27 Jan '06

Hi, I would like to create a scripting language, similar to Ruby, Perl and Python. Pugs, written in Haskell, is a Perl6 implementation. Is Haskell a good choice for me? I have no experience with Haskell (yet), but I like the concept of functional programming. Because Haskell will probably be too slow for the final implementation, I will have to rewrite it in C or maybe D. Haskell can be very useful as a test/prototype implementation, where speed is not very important. But will I be able to create a clean, and easy to understand implementation in Haskell? The scripting language will be object oriented, and imperative. Is that a problem because Haskell is functional, or is there be an obvious and nice way to implement an imperative scripting language? The language is very dynamic, and the source-tree needs to be in memory because it is modifiable at run-time. Would it be good to do this in Haskell, and port it to C if I like the implementation, or start in C? Keep the parser/lexer for the source code in Haskell, but port only the interpreter to C? What would be a good place to start? I am reading Yet Another Haskell tutorial, and I've read the first 6 of two dozen lessons in Haskell. What to do next, practice/read more/start with the implementation of the scripting language? Thanks in advance, Jules

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Discrete event simulation
by Paul Johnson 27 Jan '06

27 Jan '06

Hi, I'm going slowly nuts here. Maybe someone can help me out. I want to do some fairly straightforward discrete event simulation. Tasks do side effects, probably in the ST monad. Every so often the current task calls "delay n" where n is a number of seconds. This puts the task back on a list of schedulable processes that is ordered by time, and then takes the head of the list and starts executing it. Part of this will be some kind of synchronisation primitive. I don't much care what it is, but somewhere I need a way to make a process wait until something happens rather than just a constant time. I think I want to use something like type Task r s a = ContT r (ST s) a But I can't see how to actually do it. I've read All About Monads. I've googled for anything to do with continuations and coroutines. I'm stuck. Can someone show me how to do it. Thanks, Paul.

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Incoherent instances can make ST monad unsound
by oleg＠pobox.com 27 Jan '06

27 Jan '06

In the recent message about regions I wrote: > Typeable constraint has reduced the problem of 'region nesting' to the > regular problem of the 'linearity' of computations -- which is already > solved in ST monad. We can add that pervasive 's' type parameter to > our Q and IOM types. However, the simpler approach is just to use our > 'mark' as that 's' parameter. A small qualification should be added: although adding the 's' parameter in addition to the unexported Z parameter we had before is sound in all circumstances, the `simpler approach' may actually fail: it is possible to declare an instance "Typeable a" -- and given enough extensions, persuade GHC *and* Hugs to accept the code. The problem with IO regions would be the least of our worries however: in these circumstances, many things break, including the ST monad. One can indeed break the essential guarantee of the ST monad -- for example, create a top level STRef *and* fruitfully use in arbitrary ST computations. The enclosed code does exactly that. Thus, unsafePerformST becomes expressible in Haskell, given enough features. The presence of top-level mutable cells breaks the referential transparency. Hopefully the authors of Haskell' and Haskell2 would attach all-upper-case warnings to these extensions. The code below runs with GHC 6.4.1 (extensions are indicated inline). It also runs with Hugs, as hugs -98 +O /tmp/st.hs {-# OPTIONS -fglasgow-exts #-} {-# OPTIONS -fallow-undecidable-instances #-} {-# OPTIONS -fallow-overlapping-instances #-} {-# OPTIONS -fallow-incoherent-instances #-} module STTest where import Control.Monad.ST import Data.Typeable import Data.STRef import Data.Dynamic instance Typeable a where typeOf _ = mkTyConApp (mkTyCon "Anything goes") [] -- test1 = runST ( newSTRef 'a' ) leakedST = runST ( newSTRef 'a' >>= return . toDyn ) test3 :: Char test3 = runST (readSTRef $ ((fromDyn leakedST undefined)::STRef s Char)) {- result: *STTest> leakedST <<STRef Anything goes Char>> *STTest> test3 'a' -}

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ANNOUNCE: C-- compiler frontend release
by Robert Dockins 27 Jan '06

27 Jan '06

Fellow Haskellers and C-- enthusiasts, I am pleased to announce the initial alpha release of a C-- frontend (parser, pretty printer, and semantic checker) written in Haskell. My goal when beginning this project was to create a modular frontend that could be used both by people writing and by those targeting C-- compilers. This implementation attempts to follow the C-- spec as exactly as possible. Please enjoy. You can get the source from the darcs source repository with the following command: darcs get --partial --tag '0.1' http://www.eecs.tufts.edu/~rdocki01/cmm/ or you may simply browse the source at the above address. Cmm Frontend -========================- == What is it? This package is a C-- frontend, including a lexer (scanner), parser, pretty-printer and semantic checker. It also includes a unit test suite. == Why do I care? The Cmm frontend allows you to target C-- easily by using the pretty printer or to fill in the backend of a C-- compiler without having to deal with the uninteresting details of parsing. == How is it licensed? The Cmm frontent is avaliable under a BSD3 license. See the LICENSE file for details. == How do I build it? Cmm frontend uses a Cabal build system. The follwing commands assume you have a haskell interpreter in your system path named 'runhaskell'. All commands are run from this directory. To install for the whole system: runhaskell Setup.hs configure runhaskell Setup.hs build runhaskell Setup.hs install To install for a single user: runhaskell Setup.hs configure --prefix=/home/<username> runhaskell Setup.hs build runhaskell Setup.hs install --user To build the API docs: runhaskell Setup.hs haddock == Who is responsable for this mess? You can send bug reports, rants and comments to: Robert Dockins <robdockins AT fastmail.fm> Rob Dockins Speak softly and drive a Sherman tank. Laugh hard; it's a long way to the bank. -- TMBG

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