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Announcing hmp3 0.3
by dons＠cse.unsw.edu.au 14 Dec '05

14 Dec '05

A new version of hmp3 has been released, hopefully the last stable release for a while. Pretty much all features are done now. This release features, in particular, improved portability: * a simpler curses binding, requiring only basic XSI curses * thus runs on older OSs (Irix and Solaris at least) * b/w terminals should be handled properly * more state is stored persistently. * the binary size has shrunk Available as a cabalised src tarball, a darcs repo, and binaries for (currently): * Linux/x86 * FreeBSD/x86 * OpenBSD/x86 * OS X/ppc * Irix/mips64 http://www.cse.unsw.edu.au/~dons/hmp3.html Cheers, Don

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[ANNOUNCE]: Ranged Sets
by Paul Johnson 14 Dec '05

14 Dec '05

From the README: Ranged sets allow programming with sets of values that are described by a list of ranges. A value is a member of the set if it lies within one of the ranges. The ranges in a set are ordered and non-overlapping, so the standard set operations can be implemented by merge algorithms in O(n) time. Obviously you can use this for sets of numbers, including things like Double that tend not to fit well into the enumerated membership model of conventional set implementations. But you can also have ranges of strings (or any other list of ordered types). So for example the set of all strings from "bar" to "foo" and "BAR" to "FOO" inclusive would be: strSet = rangedSet [ Range (BoundaryBelow "bar") (BoundaryAbove "foo"), Range (BoundaryBelow "BAR") (BoundaryAbove "FOO")] Note that this set includes "bar1" but not "foo1". I've created a SourceForge project for this, although I hope that once the library matures it will be included in the Base library package. The home page is at https://sourceforge.net/projects/ranged-sets/ I *think* I've also put the source in CVS, although at present the CVS web browser on SourceForge has not caught up with it. Paul.

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PADL Deadline for Reduced Registration rate extended to 20th Dec.
by Logic Programming Rsrch Association 14 Dec '05

14 Dec '05

-------------------------------------------------------------------------------- CALL FOR PARTICIPATION CALL FOR PARTICIPATION [- Deadline for early registration extended to: Dec 20th.] Eighth International Symposium on Practical Aspects of Declarative Languages PADL 06 Charleston Place Hotel Charleston, South Carolina January 9-10, 2006 http://www.cs.brown.edu/people/pvh/PADL06.html Co-located with ACM's Principles of Programming Languages, (POPL Dates: January 11-13, 2006) You are cordially invited to attend the 8th Symposium on Practical Aspects of Declarative Languages to be held in Charleston, SC. PADL has a very interesting program that includes invited speakers as well contributed papers. Contributed papers range over diverse topics: from bioinformatics to music modeling to semantic web. Invited Speakers: Phil Wadler, University of Edinburgh, speaking on Links: Linking Theory to Practice for the Web David Roundy, Cornell University Implementing and verifying the darcs patch formalism Erik Meijer, Microsoft Research (title TBA) Contributed papers: Using CHRs to generate functional test cases for the Java Card Virtual Machine Sandrine-Dominique GOURAUD and Arnaud GOTLIEB. Generic Cut Actions for External Prolog Predicates Tiago Soares, Ricardo Rocha and Michel Ferreira. Controlling search space materialization in a practical declarative debugger Ian MacLarty and Zoltan Somogyi. Automatic Verification of a Model Checker by Reflection Bow-Yaw Wang. Probabilistic-logical Modeling of Music Jon Sneyers, Joost Vennekens and Danny De Schreye. Using Dominators for Solving Constrained Path Problems Luis Quesada, Peter Van Roy, Yves Deville and Raphakl Collet. JQuery: A Generic Code Browser with a Declarative Configuration Language Kris De Volder. A Hybrid BDD and SAT Finite Domain Constraint Solver Peter Hawkins and Peter Stuckey. Adding constraint solving to Mercury Ralph Becket, Maria Garcia de la Banda, Kim Marriott, Zoltan Somogyi, Peter Stuckey and Mark Wallace. Modeling Genome Evolution with a DSEL for Probabilistic Programming Martin Erwig and Steve Kollmansberger. Tabling in Mercury: Design and Implementation Zoltan Somogyi and Konstantinos Sagonas. Translating Description Logic Queries to Prolog Zsolt Nagy, Gergely Lukacsy and Piter Szeredi. Efficient top-down set-sharing analysis using cliques Jorge Navas, Francisco Bueno and Manuel Hermenegildo. Querying Complex Graphs Yanhong A. Liu and Scott D. Stoller. Incremental Evaluation of Tabled Prolog: Beyond Pure Logic Programs Diptikalyan Saha and C. R. Ramakrishnan.

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Re: Announcing Djinn, new version 2004-12-13
by Roy Dyckhoff 14 Dec '05

14 Dec '05

Chung-chieh Shan wrote: >I wonder why the only Church numerals Djinn found were 0 and 1? > > Djinn> :set +m > Djinn> num ? (a -> a) -> (a -> a) > num :: (a -> a) -> a -> a > num x1 x2 = x1 x2 > -- or > num _ x2 = x2 > >Very cool, in any case. > > Ken My answer would be the same as Lennart's; in detail, the point of this calculus (or, rather, the G4ip calculus on which the implementation is based) is that it is terminating---proofs are of bounded depth. (No loop-checking or tricks like "iterative deepening" are required.) The idea for the calculus goes back not to myself but to Vorob'ev (1950), and was rediscovered around 1988-1990 by several people, notably (and independently) Joerg Hudelmaier (Arch. Math. Logic 1992; JLC 1993), Pat Lincoln et al (LICS 1991) and myself (JSL 1992). I called the calculus "LJT"(the "T" is for terminating) and abandoned this when Herbelin later named two important related calculi "LJT" and "LJQ". "G4ip" is the name used in the Basic Proof Theory book by Troelstra & Schwichtenberg. Roy -- ------------------------------------------------------------------------ Roy Dyckhoff e-mail: rd(a)dcs.st-and.ac.uk (Researcher; Senior Lecturer; Director of Teaching; ...) School of Computer Science University of St Andrews tel: +44-1334-463267 North Haugh, St Andrews, ^fax: +44-1334-463278 Fife, KY16 9SX, Scotland secr: +44-1334-463253 *mob: +44-7985-266847 Home page: http://www.dcs.st-and.ac.uk/~rd * Mobile number is for emergency use only ;-) ^ There's also a personal e-fax number: +44-8707-064-446, which then sends me an e-mail with the fax as an attachment.

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Re: ECT and SearchPath
by S. Alexander Jacobson 13 Dec '05

13 Dec '05

On Tue, 13 Dec 2005, Sven Moritz Hallberg wrote: > is a good scheme. For it to _really_ work, however, we should form a > registry of "officially assigned" module names (i.e. ones without a > disambiguation suffix) and also one for the author and/or organization > names to be used as suffixes. I for example am known by the nickname > Pesco, or (more recently) by the mnemonic SM at domain KHJK.ORG. My solution to this problem in SearchPath is module maps. SearchPath lets you use multiple module maps simultaneously. So you can for example simultaneously use a global module map as haskell.org, an industry module map at yourassociate.org, an internal company map located on your_intranet, and a personal map located on your computer. Conflicts are handled by the order in which you invoke the maps. So a map is official to the extent your community shares it. Different entities can also compete to provide maps of differing qualities e.g. is the map audited for security issues? does the map point to the repository head of all modules or a static version? etc. Clay Shirky famously observed that in namespace construction there is a pretty direct tradeoff between have names be memorable, global, and non-political. I think shared module maps represents a good compromise. >> I just >> read your ECT article which seems to start with the same assumption and >> takes the theory to its logical conclusion. > > I take that as a compliment. ;) Thank you. It was intended that way! :-) > The main issue that springs to my mind is authenticity control. How do I > know the module I'm downloading is the one I want? Note that this > question is always there, even in the local case, but it is usually not > seen as a problem until module sources are distributed over the Net. I think https URLs solve this problem. You choose module maps from authors you trust and access those maps via https. These "friendly" module maps then point to "friendly" modules that you can also access via https. Since, you choose which CAs you trust to sign server keys, you are safe from MITM attacks. Note, I thought about supporting pgp but there is no obvious way to sign a CVS/SVN/darcs repository and what I like about ECT is that you can point to such repositories rather than specific checked out versions in the comfort that things won't break. I LOVE that in combination with ECT, you get notified that you are using a deprecated version on the next compile without having to check all your imports manually. FYI, the main thing that I would really like, but don't have and can't implement, is for :r in ghci to invoke SearchPath to hunt for missing modules rather than forcing you to quit out and restart ghci every time you add an import of an undownloaded module in your code. Using searcpath make thing very smooth, but this feature would make it completely so. -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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RE: [Haskell] TArray?
by Simon Marlow 13 Dec '05

13 Dec '05

On 13 December 2005 13:11, Sebastian Sylvan wrote: > On 12/13/05, Tomasz Zielonka <tomasz.zielonka(a)gmail.com> wrote: >> On Tue, Dec 13, 2005 at 01:32:46PM +0100, Sebastian Sylvan wrote: >>> Are there plans to include a mutable array for use in the STM monad, >>> or a good reason for why this is not needed? Also, an unboxed >>> version would be nice. >> >> Why not use an (Array idx (TVar a)) ? > > Ah.. Good thinking! > This should work for in the STM monad for anything you would IOArray > for in the IO monad, if you write proper instances for MArray of > course... > > It's a bit inefficient, an extra indirection (compared to a primitive > implementation) but that shouldn't matter too much for the general > case. And the TVars themselves introduces some extra overhead, I would > suppose (which could be per-array rather than per-element, without > losing the property that only writes to the same element causes > retries). > It gets even trickier if you want an unboxed mutable array in the STM > monad. > > But still, it's useful and I think a mutable array for the STM monad > should be in the libraries. It could be implemented as an Array at > first, and perhaps later switch to a more efficient representation. In the past I have used arrays of TVars, as Thomasz suggested. It would indeed be better to have a primitive STM array, the only problem with this is the extra complexity. One simplifying assumption is that it should consider changes at the level of the whole array, rather than per-element (otherwise you'd use an array of TVars). Cheers, Simon

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ETAPS 2007 - Call for Satellite Events
by joost.visser＠di.uminho.pt 13 Dec '05

13 Dec '05

------------------------------------------------------------------- ETAPS 2007: CALL FOR SATELLITE EVENT PROPOSALS deadline: January 20, 2006 ------------------------------------------------------------------- ETAPS 2007 European Joint Conferences on Theory And Practice of Software March 24 - April 1, 2007 Braga, Portugal http://www.di.uminho.pt/etaps07/ -- ABOUT ETAPS -- The European Joint Conferences on Theory and Practice of Software (ETAPS) is the primary European forum for academic and industrial researchers working on topics relating to Software Science. ETAPS is an annual event which takes place in Europe each spring since 1998. The tenth meeting, ETAPS 2007, will take place March 24 till April 1 2007 in Braga, Portugal, hosted by the University of Minho. The main conferences of ETAPS are: - FOSSACS: Foundations of Software Science and Computation Structures - FASE: Fundamental Approaches to Software Engineering - ESOP: European Symposium on Programming - CC: International Conference on Compiler Construction - TACAS: Tools and Algorithms for the Construction and Analysis of Systems These conferences will take place March 26-30, 2007. -- SATELLITE EVENTS -- The ETAPS 2007 Organizing Committee invites proposals for Satellite Events (workshops, tutorials, etc.) that will complement the main ETAPS conferences. They should fall within the scope of ETAPS. This encompasses all aspects of the system development process, including specification, design, implementation, analysis and improvement, as well as the languages, methodologies and tools which support these activities, covering a spectrum from practically-motivated theory to soundly-based practice. Satellite Events provide an opportunity to discuss and report on emerging research approaches and practical experience relevant to theory and practice of software. ETAPS 2007 Satellite Events will be held immediately before and after the main conferences, on March 24-25 and March 31, and April 1, 2007. -- SUBMISSION OF SATELLITE EVENT PROPOSALS -- Researchers and practitioners wishing to organize Satellite Events are invited to submit proposals in ASCII, PDF or Postscript format by e-mail to the Satellite Events Co-chairs, Luis Barbosa and Joost Visser, mailto:joost.visser@di.uminho.pt. A proposal should not exceed two pages and should include: - Satellite Event name / acronym - the names and contact information of the organizers - the preferred period: 24-25 March or 31 March-1 April - the duration of the workshop: one-day or two-day event - 120-word description of the workshop topic for later use in publicity material - a brief explanation of the workshop topic and its relevance to ETAPS - a schedule for paper submission, notification of acceptance and final versions (the latter no later than the early registration deadline of February 12, 2007) - expected number of participants - any other relevant information, like event format, invited speakers, publication policy, demo sessions, special space requirements, etc. The proposals will be evaluated by the ETAPS 2007 organizing committee on the basis of their assessed benefit for prospective participants to ETAPS 2007. The titles and brief information about accepted Satellite Events will be included in the ETAPS 2007 web site, call for papers and call for participation. Satellite Events organizers will be responsible for - producing the event's call for papers and call for participations - publicising the event through specialist mailing lists etc. to complement publicity for ETAPS as a whole - hosting and maintaining a web site for the event - reviewing and making acceptance decisions on submitted papers - producing the event proceedings, if any; facilities for printing will be made available by the ETAPS organizers - scheduling workshop activities in consultation with the local organizers Prospective organizers may wish to consult the web pages of previous satellite events as examples: ETAPS 2006: http://www.complang.tuwien.ac.at/etaps06/ ETAPS 2005: http://www.etaps05.inf.ed.ac.uk/ ETAPS 2004: http://www.lsi.upc.es/etaps04/ ETAPS 2003: http://www.mimuw.edu.pl/etaps03/ -- IMPORTANT DATES -- Satellite Event Proposals Deadline: 20 January 2006 Notification of acceptance: 6 February 2006 -- FURTHER INFORMATION AND ENQUIRIES -- http://www.di.uminho.pt/etaps07/ etaps07(a)di.uminho.pt Luis Barbosa Joost Visser ETAPS 2007 Satellite Events Co-chairs lsb(a)di.uminho.pt, joost.visser(a)di.uminho.pt -- THE HOST CITY -- Braga, capital of the Minho province, is an ancient city in the heart of the green and fertile region known as the Costa Verde. The region is known for its attractiveness in terms of climate, gastronomy, prices, and culture. The region is served by the Oporto international airport, providing direct flights to many major European cities. Braga is known for its barroque churches and splendid 18th century houses. The old city is solemn and antique, but animated with commercial activity and academic life. http://www.cm-braga.com.pt/turismo/turismo.asp --

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HWN this week
by John Goerzen 13 Dec '05

13 Dec '05

Hi everyone, We had a fire at my workplace last night. It is unlikely that I will be able to get HWN out this week. (Sorry about missing it last week as well.) We'll just call the next one the Special Holiday Edition, eh? -- John

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TArray?
by Sebastian Sylvan 13 Dec '05

13 Dec '05

Are there plans to include a mutable array for use in the STM monad, or a good reason for why this is not needed? Also, an unboxed version would be nice. A workaround is IOArray with unsafePerformIO wrapped in the STM monad, but it would be preferable if multiple threads could write to the same array without causing conflicts unless they write to the same index. /S -- Sebastian Sylvan +46(0)736-818655 UIN: 44640862

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Type problem
by Emil Axelsson 13 Dec '05

13 Dec '05

Hello all, Could I please get some guidance with this? I'm working on implementing a simple relational language in Haskell. I'm trying to construct a data type that can represent values and patterns for a small set of supported types. See code below. HasX is a class of types that have an unconstrained value (xVal). Number is a typical member of that class. Val is my value/pattern data type. P represents a primitive value and T2 is used to make structure. X represents the unconstrained value or a wildcard pattern. It can only be used for types in HasX. The problem is the commented line in the value function. I want to use the xVal method to get the value for X. This is only allowed if I add the constraint (HasX a => ). But I don't want value to have that constraint, since then I cannot run it on pairs. Furthermore, it should be safe without the constraint. ex2 shows that we cannot use X to construct values that are not in HasX. Is this just a limitation of the current GATDs, or is it unreasonable of me to expect this to work? Is there any workaround, such as coercing the type of the value function? -- / Emil ******************************** {-# OPTIONS -fglasgow-exts #-} class HasX a where xVal :: a data Number = XN -- Unconstrained | N Int -- Constrained instance HasX Number where xVal = XN data Val a where P :: a -> Val a -- Primitive T2 :: (Val a1, Val a2) -> Val (a1,a2) X :: HasX a => Val a -- Unconstrained value :: Val a -> a -- value X = xVal value (P a) = a value (T2 (a1,a2)) = (value a1, value a2) ex1 :: Val (Number,(Number,Number)) ex1 = T2 (P (N 3), T2 (X, P (N 5))) -- ex2 :: Val (Number,Number) -- ex2 = X

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