May 2003 - Haskell - Haskell.org

RE: ANNOUNCE: GHC version 6.0
by Simon Marlow 29 May '03

29 May '03

> Congratulations on the new release. But out of curiosity, I've got to > ask... > > Why is the test suite now driven by a python script? Is this a > niche where a 'scripting' language was deemed more suitable than > haskell? The test driver makes use of 'eval'-style scripting, which none of the existing Haskell systems has. Template Haskell does provide a kind of 'eval', but it is compile-time rather than run-time. That's interesting though: I hadn't thought about it, but it might be possible to implement the test framework as a Haskell library which uses Template Haskell. Cheers, Simon

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RE: ANNOUNCE: GHC version 6.0
by Tim Docker 29 May '03

29 May '03

Congratulations on the new release. But out of curiosity, I've got to ask... Why is the test suite now driven by a python script? Is this a niche where a 'scripting' language was deemed more suitable than haskell?

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RE: Two minor reports concerning GHC
by Simon Marlow 29 May '03

29 May '03

> (1) unhelpful error message from GHCi: > > [[ > Compiling ParsecPrim ( F:\Haskell\Lib/ParsecPrim.hs, > interpreted ) > WARNING: ignoring polymorphic case in interpreted mode. > Possibly due to strict polymorphic/functional constructor args. > Your program may leak space unexpectedly. > ]] > I don't understand what this is trying to say, and the lack > of a source > code line number doesn't give me any chance to study the code for > clues. This warning is GHCi only. It is warning you about a bug in GHC. Fortunately, the bug has been fixed in the forthcoming 6.0 release. > (2) Strange behaviour of GHCs Time.diffClockTimes function: > > This code fragment: > [[ > runTest t = > do { st <- Time.getClockTime > ; putStr $ "Test started: "++show st++"\n" > ; runTestTT t > ; ft <- Time.getClockTime > ; putStr $ "Test finished: "++show ft++"\n" > ; let et = Time.diffClockTimes ft st > ; putStr $ "Test duration: "++show et++"\n" > } > ]] > > yields this output: > [[ > Test duration: TimeDiff {tdYear = 0, tdMonth = 0, tdDay = 0, > tdHour = 0, > tdMin = 0, tdSec = 9, tdPicosec = -437000000000} > ]] This is reasonable, as far as I can tell. The only requirement on a TimeDiff is that: t1 `addToClockTime` (t1 `diffClockTimes` t2) == t2 and the TimeDiff above does just that. It *could* be normalised so that the signs of the two components are the same, but the current implementation doesn't do that. Cheers, Simon

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Two minor reports concerning GHC
by Graham Klyne 28 May '03

28 May '03

I've noticed a couple of very minor issues with GHC[i]: (1) unhelpful error message from GHCi: [[ Compiling ParsecPrim ( F:\Haskell\Lib/ParsecPrim.hs, interpreted ) WARNING: ignoring polymorphic case in interpreted mode. Possibly due to strict polymorphic/functional constructor args. Your program may leak space unexpectedly. ]] I don't understand what this is trying to say, and the lack of a source code line number doesn't give me any chance to study the code for clues. This warning is GHCi only. (2) Strange behaviour of GHCs Time.diffClockTimes function: This code fragment: [[ runTest t = do { st <- Time.getClockTime ; putStr $ "Test started: "++show st++"\n" ; runTestTT t ; ft <- Time.getClockTime ; putStr $ "Test finished: "++show ft++"\n" ; let et = Time.diffClockTimes ft st ; putStr $ "Test duration: "++show et++"\n" } ]] yields this output: [[ Test duration: TimeDiff {tdYear = 0, tdMonth = 0, tdDay = 0, tdHour = 0, tdMin = 0, tdSec = 9, tdPicosec = -437000000000} ]] In particular, tdSec and tdPicosec have different signs. I don't see what reasonable implementation would yield such a result. I've observed this with programs running interactively under GHCi, and also stand-alone executables. These tests using GHC 5.04.3, on Windows 2000. #g -- BTW, I found the GHC profiler to be very useful, and easy to use. I'm impressed! ------------------- Graham Klyne <GK(a)NineByNine.org> PGP: 0FAA 69FF C083 000B A2E9 A131 01B9 1C7A DBCA CB5E

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St.Eve CfP - FM'03 Satellite -
by mailinglist-admin＠fmeurope.org 28 May '03

28 May '03

(Please find attached printable versions of the CfP below) ******************************************************************** CALL FOR PAPERS ******************************************************************** --- ST.EVE --- State-oriented vs. Event-oriented thinking in Requirements Analysis, Formal Specification and Software Engineering http://fme03.isti.cnr.it/SteveHomePage.html Satellite Workshop @ FM'03 (http://matrix.iei.pi.cnr.it/FMT/FME/) Pisa, Sept. 13, 2003 Popular approaches to specification are based on either states or actions (events). Abadi and Lamport ('93) observe that, while these approaches are, in some sense, equivalent ('an action can be modeled as a state change, and a state can be modeled as an equivalence class of sequences of actions'), they have taken, in the past, 'very different formal directions', and they 'tend to differ also in practice'. Some people believe that the first step in system development should be the identification of the right global state structure. Other people start characterizing the system by describing its interactions with the environment, that is, by identifying event patterns (e.g. use cases), without worrying about the state. - What is the shape of your mental landscape, when you start conceiving a complex (concurrent, reactive, distributed) system? Is it a structure of state variables (relations, functions), or a pattern of events in time? - Is the choice between a state-oriented and an event-oriented approach dependent on the type of system to be described? How? - How does a system description in natural language affect the choice between state-oriented and event-oriented formalisation? How does the requirements analysis process affect the choice? - The two approaches don't have to be mutually exclusive. Is it easy/desirable to move from one to the other? At which stage of development would one do that? - Can one integrate the two approaches, keeping their individual advantages? If so, can one formally refine a purely state-oriented or purely event-oriented description into a hybrid one? Formal specification approaches, such as ASM, B, CSP, Predicate/Transition Nets, TLA, Z, often imply a strong bias towards one or the other extreme of the 'ST.EVE' spectrum. On the other hand, software engineers often choose a language without explicitly locating it along the spectrum, the choice being driven by a mix of technical and opportunistic (if not 'religious') reasons. If you are interested into an open-minded discussion on these questions, please consider sharing your opinions and experiences with us at the Workshop, and send us a contribution. SUBMISSIONS ----------- Contributions (abstract, extended abstract, or full paper) should be submitted in PostScript or PDF format, and sent by the date below an e-mail to t.bolognesi(a)iei.pi.cnr.it and J.Derrick(a)ukc.ac.uk IMPORTANT DATES --------------- Abstract, extended abstract, or full paper June 30 Communication of acceptance July 31 PROCEEDINGS ----------- Submissions will be reviewed for relevance to the workshop, and informal proceedings will be distributed to the participants. Extended versions of high quality papers will be considered for inclusion in a Special Section of the Software and Systems Modeling Journal (Springer - http://www.sosym.org/) PROGRAMME COMMITTEE ------------------- Jean-Raymond Abrial, Egon Boerger, Tommaso Bolognesi, Michael Butler, Jim Davies, John Derrick, Vincenzo Gervasi, Susanne Graf, Wolfgang Griesgamp, Yuri Gurevich, Wolfram Schulte. ORGANISATION ------------ T. Bolognesi (CNR-ISTI, Pisa) J. Derrick (Univ. of Kent at Canterbury)

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Multiparameter classes in HUGS and GHC
by Graham Klyne 28 May '03

28 May '03

I've trying to understand better how to use multiparameter classes, and in particular the things that can be declared as instances. I've consulted the following: [1] http://www.haskell.org/onlinereport/decls.html#sect4.3.2 [2] http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.htm… (particularly 7.3.5.1 item 3) [3] http://research.microsoft.com/Users/simonpj/Papers/type-class-design-space/ [4] http://cvs.haskell.org/Hugs/pages/hugsman/exts.html (section 7.1) From my reading, it seems that while strict Haskell 98 does not permit type expressions or synonyms to be declared as class instances, both GHC and HUGS claim to relax this restriction (presumably following the analysis in [3]). My problem is that I can't get HUGS to accept a type expression or synonym to be declared as an instance of a (multiparameter) class; I'm getting the error "Illegal type in class constraint". After some wrestling with the system, I have managed to figure how to declare instances that use type constructors. I feel I may be missing something blindingly obvious. My spike code is below: the uncommented sections compile OK, but the commented-out sections do not. #g -- [[ class (Eq k, Show k) => Pair a k v where newPair :: (k,v) -> a k v getPair :: a k v -> (k,v) newtype MyPair1 k v = P1 (Int,String) instance Pair MyPair1 Int String where newPair (x,y) = P1 (x,y) getPair (P1 (x,y)) = (x,y) data MyPair2 k v = P2 Int String instance Pair MyPair2 Int String where newPair (x,y) = P2 x y getPair (P2 x y) = (x,y) data (Eq a, Show a) => MyPair3 a b = P3 a b instance Pair MyPair3 Int String where newPair (x,y) = P3 x y getPair (P3 x y) = (x,y) {- -- The following DO NOT work because instances -- "must take the form of a type constructor T applied -- to simple type variables" (though this may be relaxed -- in the multiparameter case: see [1]). -- -- Apparently, GHC *does* allow this, though HUGS -- apparently does not, though it does claim to [2]. -- -- [1] http://research.microsoft.com/Users/simonpj/Papers/type-class-design-space/ -- -- [2] http://cvs.haskell.org/Hugs/pages/hugsman/exts.html (section 7.1) -} type MyPair4 k v = (k,v) {- instance Pair (Int,String) Int String where newPair = id getPair = id instance Pair (MyPair4 Int String) Int String where newPair = id getPair = id instance Pair (MyPair4 k v) Int String where newPair = id getPair = id -} ]] I'm using the November 2002 release of HUGS with Hugs extensions enabled: [[ Current settings: +fewuiRWX -stgGl.qQkoOIHTN -h250000 -p"%s> " -r$$ -c40 Search path : -P{Hugs}\lib:{Hugs}\lib\exts:{Hugs}\lib\win32:{Hugs}\lib\hugs; {Hugs}\libraries\HUnit-1.0 Project Path : Source suffixes : -S.hs;.lhs Editor setting : -E"C:\\Program Files\\TextPad 4\\TextPad.exe" Preprocessor : -F Compatibility : Hugs Extensions (-98) ]] ------------------- Graham Klyne <GK(a)NineByNine.org> PGP: 0FAA 69FF C083 000B A2E9 A131 01B9 1C7A DBCA CB5E

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The Fun of Programming Edited by Gibbons and de Moor
by Bek, Jana 28 May '03

28 May '03

Palgrave Macmillan has recently published the above title and is looking for ways to promote it. Please would you let me have details and rates for emailing to the appropriate part of the Haskell community? Here is some more information about the book for your information. http://www.palgrave.com/catalogue/catalogue.asp?Title_Id=0333992857 Thank you. Jana Bek Marketing Manager, Computer Science W H Freeman Sinauer Associates University Science Books Palgrave Macmillan Houndmills, Basingstoke, Hampshire RG21 6XS, UK http://www.palgrave.com Palgrave Macmillan - Publisher of the Year 2003 Awarded by The Booksellers Association of the United Kingdom & Ireland Academic, Professional & Specialist Booksellers Group March 2003 DISCLAIMER: This e-mail is confidential and should not be used by anyone who is not the original intended recipient. If you have received this e-mail in error please inform the sender and delete it from your mailbox or any other storage mechanism. Neither Macmillan Publishers Limited nor any of its agents accept liability for any statements made which are clearly the sender's own and not expressly made on behalf of Macmillan Publishers Limited or one of its agents. Please note that neither Macmillan Publishers Limited nor any of its agents accept any responsibility for viruses that may be contained in this e-mail or its attachments and it is your responsibility to scan the email and attachments (if any). No contracts may be concluded on behalf of Macmillan Publishers Limited or its agents by means of e-mail communication. Macmillan Publishers Limited Registered in England and Wales with registered number 785998 Registered Office Brunel Road, Houndmills, Basingstoke RG21 6XS

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Missing class functions
by Graham Klyne 28 May '03

28 May '03

I came across a surprising feature of Haskell's class system. If I declare an instance of a class, but do not define one of the functions of that class, the compiler does not notice. Even if I try to reference the undefined function, the compiler doesn't notice. It's only when I try to evaluate the missing function, at run-time, that I get an error message. I now see this is correct behaviour: [[ If no binding is given for some class method then the corresponding default class method in the class declaration is used (if present); if such a default does not exist then the class method of this instance is bound to undefined and no compile-time error results. ]] -- [Report, section 4.3.2] Is there a rationale for allowing class methods to be undefined for an instance? #g -- [[ -- Missing class functions not detected? -- SpikeMissingClassFunctions.hs class (Show (m a), Show a) => C m a where a1 :: [a] -> m a a2 :: m a -> [a] a3 :: m a -> Bool data MyC a = MyC [a] instance (Show a) => C MyC a where a1 s = MyC s a2 (MyC s) = s instance (Show a) => Show (MyC a) where show (MyC s) = "MyC "++(show s) test1 = a1 [1,2,3] :: MyC Int -- "MyC [1,2,3]" test2 = a2 test1 -- "[1,2,3]" test3 = a3 test1 -- "Program error: Undefined member: a3" ]] Hugs log: [[ Reading file "D:\Cvs\DEV\HaskellRDF\Spike\SpikeMissingClassFunctions.hs": Hugs session for: C:\DEV\Hugs98\libraries\Hugs\Prelude.hs C:\DEV\Hugs98\libraries\Prelude.hs D:\Cvs\DEV\HaskellRDF\Spike\SpikeMissingClassFunctions.hs Main> test1 MyC [1,2,3] Main> test2 [1,2,3] Main> test3 Program error: Undefined member: a3 ]] ------------------- Graham Klyne <GK(a)NineByNine.org> PGP: 0FAA 69FF C083 000B A2E9 A131 01B9 1C7A DBCA CB5E

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HLPP 2003 Call for participation
by F. Loulergue 27 May '03

27 May '03

************************************************************************ HLPP 2003: Second International workshop on High-level parallel programming and applications Call for participation Monday/Tuesday 16-17 June, 2003 Paris, France Detailed informations: http://hlpp.free.fr ************************************************************************ Many applications of computing require performance levels attainable only on parallel architectures. Such systems are now readily available as their price/performance ratio continues to improve. The rapid development of affordable hardware for parallel computing makes the need to develop high-quality parallel software increasingly urgent. Sequential programming has long benefited from high-level programming techniques and tools that have made today's immense range of software economically viable. Two decades of research into high-level parallel programming has produced methods and tools that improve the price/performance ratio of parallel software, and broaden the range of target applications. GRIDs offer a tremendous computing power. Nevertheless, this power is far from being effectively exploited. In addition to technical problems related to portability and access, Grid computing needs new programming paradigms. Research on high level grid programming is particularly relevant. This workshop follows HLPP 2001 and is aimed at - computer science researchers, practitioners, graduate students - scientific computing researchers, practitioners, graduate students - high-performance application developers (e.g. in DBMS, data-mining, parallel model checking, virtual reality) Invited Lecture --------------- The Real-Time Revolution Bill McColl Professor of Computer Science, Oxford University Founder and CTO, Sychron Inc Presentations ------------- Eskimo : Experimenting Skeletons on the Shared Address Model Marco Aldinucci Pipelining a Skew-insensitive Parallel Join Algorithm Mostafa Bamha, Matthieu Exbrayat Top-Down Design of Bulk-Synchronous Parallel Programs Yifeng Chen, J. W. Sanders A Calculus for Dense Array Distributions Roberto Di Cosmo, Susanna Pelagatti llc: A parallel skeletal language Antonio J. Dorta, Jesus A. Gonzalez, Casiono Rodriguez and Francisco de Sande Formal Proofs of Functional BSP Programs Frederic Gava Automatic Skeletons in Template Haskell Kevin Hammond, Jost Berthold, Rita Loogen High Level Parallel Software Development with Python and BSP Konrad Hinsen Aligned Multithreaded Computations and Performance Guarantees Xie Jong, Hsu Wen-Jing DatTel: A Data-parallel C++ Template Library Holger Bischof, Sergei Gorlatch, and Roman Leshchinskiy Extending OpenMP for Task Parallelism Ami Marowka SaC - From High-Level Programming with Arrays to Efficient Parallel Execution Clemens Grelck, Sven-Bodo Scholz BSPGRID: Variable Resources Parallel Computation and Multiprogrammed Parallelism Vasil Vasiliev Accepted papers will be published in special issues of Parallel Processing Letters, World Scientific Publishing (provided revisions suggested by the referees are made). Programme committee and organizers ---------------------------------- Rob Bisseling (Netherlands) Murray Cole (United Kingdom) Gaetan Hains (France) Herbert Kuchen (Germany) Frederic Loulergue (France) Quentin Miller (United Kingdom) David Skillicorn (Canada) Contact : Frederic Loulergue (LACL, France) <loulergue(a)univ-paris12.fr> Registration ------------ Participants must register by Friday 6 June. The workshop fee ranges from 50 Euros (without dinner) to 140 Euros (with 2 dinners). See http://hlpp.free.fr/registration/formulaire.html for registration details. Venue ----- The workshop is being held in Paris at the Laboratory "Preuves, Programmes et Systemes" 175, rue du Chevaleret 75013 Paris Dates ----- Friday 6 June 2003 : deadline for registration Sunday 15 June 2003 : Dinner Monday 16 June 2003 : Invited Lecture by Pr. W.F. McColl presentation of papers Dinner Tuesday 17 June 2003 : presentation of papers; workshop ends at noon ************************************************************************ _______________________________________________ skeletons mailing list skeletons(a)inf.ed.ac.uk http://lists.inf.ed.ac.uk/mailman/listinfo/skeletons

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(no subject)
by Stefano Bistarelli 27 May '03

27 May '03

============================================================================ ======= 5th International Workshop on Soft Constraints Held in conjunction with 9th International Conference on Principles and Practice of Constraint Programming, CP2003 Actons Hotel, Kinsale, County Cork, Ireland. 29 September - 3 October, 2003 http://www.sci.unich.it/~bista/organizing/soft-2003/ ============================================================================ ======== Call for Paper ============================================================================ ======== Soft-constraints augment the classical CSP framework by allowing the user to express preferences among potential solutions. Given a well-defined mechanism to express and combine preferences, the goal is to find the "best" solution. Therefore, solving soft constraints becomes an optimization task, harder than the satisfaction tasks in classical CSP. Sometimes optimization becomes multi-objective, making the solving process even more complex. The interest of the community on soft constraints has increased in the last years. Several theoretical frameworks have been developed to allow soft constraints in problem modeling. For these frameworks, new algorithms have been built. The main motivation for this line of research is the existence of many real problems involving preferences among potential solutions, which demand an effective solving method. Also in this edition, we want to enlarge the workshop scope by encouraging submissions from domains where soft constraints have specific semantics such as propositional logic formulae (i.e. MAX-SAT), probability distributions (i.e. probabilistic reasoning) or uncertainty. Workshop topics include (but are not limited to): 1. theoretical frameworks for soft constraints 2. problem modeling with soft constraints 3. solving algorithms for soft constraints 4. interlacing satisfaction and optimization techniques 5. multi-objective optimization and soft constraints 6. constraint languages including soft constraints 7. combining/integrating soft constraint frameworks and algorithms into the Constraint Programming framework 8. comparative studies 9. real-life applications Delivery & Submissions This workshop is intended to build on the experience and success of the CP99, CP2000, CP2001 and CP2002 workshops on the same subject, and its aim is to provide a forum where researchers currently working in this area can discuss their most recent ideas and developments and think together about the most promising new directions. Therefore we encourage the presentation of work in progress or on specialized aspects of soft constraints. Papers that bridge the gap between theory and practice are especially welcome. Prospective attendees can Submit a paper, which can be up to 15 pages in length. We encourage authors to submit papers electronically in postscript or pdf format. Papers should be formatted using the Lecture Notes in Computer Science (LNCS) style. Please send your submissions by email to larrosa(a)lsi.upc.es using the subject line Soft-2003 Workshop Submission. Important Dates The proposed schedule of important dates for the workshop is as follows: Paper Submission deadline June 24th Notification of acceptance July 24th Camera-ready version deadline August 14th Workshop Date September 29th Workshop Organizers: Stefano Bistarelli Istituto per l'Informatica e la Telematica, C.N.R., Pisa, Italy Stefano.Bistarelli(a)iit.cnr.it Dipartimento di Scienze, Universita' degli Studi "G. D'Annunzio", Pescara, Italy bista(a)sci.unich.it Javier Larrosa Universitat Politècnica de Catalunya, Barcelona, Spain larrosa(a)lsi.upc.es Thomas Schiex Institut National de La Recherche Agronomique, Castanet Tolosan Cedex - France tschiex(a)toulouse.inra.fr Program Committee: Fadi Aloul (Electrical Engineering & Computer Science University of Michigan - Ann Arbor, USA) Hélène Fargier (IRIT, Université Paul Sabatier, France) Thom Fruehwirth (University of Ulm, Germany) Carmen Gervet (IC-Parc, Imperial College, UK) Ulrich Junker (ILOG, France) Jimmy H. M. Lee (The Chinese University of Hong Kong, Hong Kong) Pedro Meseguer (IIIA-CSIC, Bellaterra, Spain) Barry O'Sullivan (University College Cork, Ireland) Francesca Rossi (University of Padova, Italy)

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