- Haskell - Haskell.org

Re: FiniteMap performance WITHOUT any copying?
by George Russell 08 Feb '03

08 Feb '03

Magnus wrote (snipped) > Now, Haskell has a garbage collector, so Haskell must know how many > pointers there are to all objects in the heap (or?). Then, if a finite map > for example only has one single pointer to it, then it ought to be all > right to modify the finite map (or whatever datastructure we are > considering), I mean really modify the map without making any copies, just > like in imperative languages. Perhaps there might be pointers to nodes > inside the tree and I guess that could complicate the matter somewhat. But > for Haskell arrays it ought to be possible to really modify the array if > it is used by only one pointer ? > > Are such optimizations possible, and if they are, are they already > implemented in for example GHC ? Or am I wrong somewhere ? I think it unlikely that such an optimisation is implemented for GHC, which is as a rule extremely unwilling to modify "functional" data. The trouble with this kind of thing is that although it seems neat, it is hard to implement, and also opens up cans of worms all over the place; for example by making generational garbage collection harder to implement. In fact I don't think GHC does know how many pointers there are to all objects in the heap. That would only be useful if it did GC by reference-counting, which it doesn't. Reference counting is in fact rather expensive; as well as requiring an extra field on every item to hold the number of references, you need to add lots of operations to increment these fields every time you create or delete a new reference. Also of course reference counting will not be able to free circular structures, at least not in general with data being modified.

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Re: FiniteMap performance WITHOUT any copying?
by Zdenek Dvorak 08 Feb '03

08 Feb '03

Hello, >Now, Haskell has a garbage collector, so Haskell must know how many >pointers there are to all objects in the heap (or?). Then, if a finite map >for example only has one single pointer to it, then it ought to be all >right to modify the finite map (or whatever datastructure we are >considering), I mean really modify the map without making any copies, just >like in imperative languages. Perhaps there might be pointers to nodes >inside the tree and I guess that could complicate the matter somewhat. But >for Haskell arrays it ought to be possible to really modify the array if >it is used by only one pointer ? > >Are such optimizations possible, and if they are, are they already >implemented in for example GHC ? Or am I wrong somewhere ? You are more or less right; except that -- the Haskell implementations I have seen do not keep number of pointers to objects (gc in principle works by traversing the graph made by pointers, marking reachable nodes and finally removing the unreachable ones; just keeping the number of references is not sufficient due to cyclic structures) -- due to lazy evaluation, the situation where there would be just one pointer to array is rare Zdenek _________________________________________________________________ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail

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filter and Prelude index in H98 report?
by Antony Courtney 07 Feb '03

07 Feb '03

Hi all, Is there any deep reason why "filter" does not appear in the "Index of the Haskell 98 Prelude", found at: http://www.haskell.org/onlinereport/prelude-index.html Thanks, -antony -- Antony Courtney Grad. Student, Dept. of Computer Science, Yale University antony(a)apocalypse.org http://www.apocalypse.org/pub/u/antony

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SBLP 2003 - extended deadline
by Lucilia Camarao de Figueiredo 07 Feb '03

07 Feb '03

CALL FOR PAPERS SBLP 2003 - 7th Brazilian Symposium on Programming Languages Ouro Preto, MG, Brazil - May 28-30, 2003 http://www.inf.pucminas.br/sblp2003 ******** Extended deadline: February 24th ****** ***** PROCEEDINGS WILL BE PUBLISHED AS A VOLUME OF THE ***** "Journal of Universal Computer Science" (www.jucs.org) Scope The Brazilian Symposium on Programming Languages (SBLP), sponsored by the Brazilian Computer Society (SBC), is a forum where researchers, educators, and practitioners can present and discuss the fundamental principles and innovations in the design, analysis and implementation of programming languages and systems. We invite authors to contribute to SBLP 2003 with the following kinds of submissions: - Technical research papers introducing original research results on topics such as (but not limited to): programming language design and implementation, formal semantics of programming languages, domain-specific programming languages, programming languages for mobile, WWW, and network computing, script languages, new programming models, theoretical foundations of programming languages and teaching programming languages. - Tutorial proposals on subjects related to programming languages, APIs, tools, environments or theories, at graduate level. Important Dates - Deadline for submissions (extended): *** February 24th, 2003 *** - Notification of acceptance: March 28th, 2003 - Camera-ready version: April 17th, 2003 Invited Speakers Nick Benton Programming Principles and Tools group Microsoft Research, Cambridge http://research.microsoft.com/~nick Simon Thompson Computing Laboratory University of Kent http://www.cs.ukc.ac.uk/people/staff/sjt Submission Guidelines Contributions can be written in Portuguese, English or Spanish. Papers should have at most 14 pages. All papers will be published in the conference proceedings. Tutorial submissions may be in the form of a proposal. The final version of a selected tutorial should contain at most 30 pages and will be published in separate proceedings. Please check the symposium web site for more information about submissions guidelines and procedures. Program Committee Luis Barbosa, Universidade do Minho Roberto Bigonha, UFMG Mariza Bigonha, UFMG Paulo Blauth Menezes, UFRGS Paulo Borba, UFPE Christiano Braga, UFF Carlos Camarao, UFMG Renato Cerqueira, PUC-Rio Jose Luiz Fiadeiro, University of Leicester Alex Garcia, IME Jose Guimaraes, UFSCAR Hermann Haeusler, PUC-Rio Roberto Ierusalimschy, PUC-Rio (chair) Jose Emilio Labra, Univesidad de Oviedo Rafael Dueire Lins, UFPE Alfio Martini, PUC-RS Ricardo Massa, UPE Dale Miller, INRIA Hermano Moura, UFPE Martin Musicante, UFPR David Naumann, Stevens Institute of Technology Catuscia Palamidessi, INRIA Futurs Uday Reddy, University of Birmingham Noemi Rodriguez, PUC-Rio Cecilia Rubira, Unicamp Andre Santos, UFPE Marco Tulio Valente, PUC-MG Organizing Committee Lucilia Figueiredo (UFOP) - Chair Marco Tulio Valente (PUC Minas) Mariza Bigonha (UFMG) Symposium Location Listed by UNESCO as a World Heritage landmark, Ouro Preto ("black gold" in portuguese) gathers one the largest collections of baroque art in the world. Its churches, museums and public monuments attract tourists from all over the world. The city is located 100 km from Belo Horizonte, one of the largest cities from Brazil, in the state of Minas Gerais. More Information For further information, visit the symposium web site at http://www.inf.pucminas.br/sblp2003 or send e-mail to sblp2003(a)pucminas.br

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RE: [OT] Teaching Haskell in High School
by Kevin Millikin 07 Feb '03

07 Feb '03

On Friday, February 07, 2003 7:41 AM, Arjan van IJzendoorn [SMTP:afie@cs.uu.nl] wrote: > The quality of the messages, however, is not as good as I would have > expected. I am a beginning Scheme programmer ... Then you should have set the language to "Beginning Student" or "Beginning Student with List Abbreviations". Seriously. A nice thing about the DrScheme environment is that it allows languages to be layered. Instructors don't have to wave their arms ands say "pay no attention to 'public static void' and 'String[] args' and 'class TestExp {'" just to begin writing simple programs. The DrScheme languages are restricted subsets of Scheme. The same could certainly be done in a learning environment for Haskell, but is more difficult in Java or C++. Even if the student is told to "ignore" some things for now, many of the problems they have are often caused by not understanding the things they're supposed to be ignoring--which can be incredibly frustrating. If you had set the DrScheme language to one of the two "Beginning Student" levels, you would have seen: function call: expected a defined name or a primitive operation name after an open parenthesis, but found a number And "+1" would have been highlighted. This would have been reported when you entered the *definition* for length2, not when you applied it. Switch to "Intermediate Student", and you get: function call: expected a name after an open parenthesis, but found a number With "+1" highlighted, at definition of length2. Switch to "Intermediate Student with lambda" or "Advanced Student", and the definition is accepted, but the application (to a non-empty list) reports: procedure application: expected procedure, given: 1; arguments were: 0 > I think it is important that error messages show exactly what was > entered by the user (+1 and not 1) and that's why in Helium we > remember each little detail in the abstract syntax tree. Excellent idea. > I still don't know what "arguments were: 1" means. Does it refer to > the number of arguments? Are you sure you it said that? Mine doesn't ;). I expect "arguments were: 0". It was complaining about trying to apply "1" to the argument that is the value of (length2 empty), which should be zero, no?

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Re: default class methods in sub-classes
by Zdenek Dvorak 06 Feb '03

06 Feb '03

Hello, >Apparently I can't do this (in ghc or hugs -- haven't tried others): > >class Space a where > distance :: a -> a -> Int > subtract :: a -> a -> a > >class (Space a) => NormSpace a where > norm :: a -> Int > distance a b = norm (subtract a b) > >That is, I can't make (or redefine) a default for the superclass method >'distance' in a subclass. I agree that the Haskell'98 definition doesn't >claim that this should be allowed, but it seems like something that would >be >useful. Are there reasons not to allow this (or that I shouldn't want to >do >this at all)? > >Apologies if this is well-covered. I couldn't find any mention of it. the problem is, that to make something instance of NormSpace, you must first have it as instance of Space, i.e. with distance already defined. Then for this to work, the default definition in NormSpace would have to override what user defined, which looks strange. Your problem can be solved in ghc by this (but unfortunately only with -fallow-overlapping-instances -fallow-undecidable-instances (or some simmilar flags)): class HavingSubtract a where -- not sure why generic space should have subtract, subtract :: a -> a -> a -- but why not class (HavingSubtract a) => Space a where distance :: a -> a -> Int class (HavingSubtract a) => NormSpace a where norm :: a -> Int instance (NormSpace a) => Space a where distance a b = norm (subtract a b) (and there is several more examples in that I would find something like this very useful, but AFAIK there is no clean and elegant way how to do it -- you may do something simmilar using newtypes, but that is totally clumsy). Zdenek _________________________________________________________________ The new MSN 8: smart spam protection and 2 months FREE* http://join.msn.com/?page=features/junkmail

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CFP: APLAS03 - 1st Asian Symp. on Prog. Lang. and Systems
by Manuel M T Chakravarty 06 Feb '03

06 Feb '03

[My apologies if this eventually leads to a double posting, but Atsushi Ohori's original post didn't get through as he does not subscribe to this list.] Call for Papers The First Asian Symposium on Programming Languages and Systems (APLAS03) URL: http://www.jaist.ac.jp/aplas/ Beijing, China. October 27-29, 2003 (Submission deadline: May 27, 2003) Sponsored by the Asian Association for Foundations of Software (AAFS) and Beihang University (Beijing University of Aeronautics and Astronautics). DESCRIPTION: APLAS aims at stimulating programming language research by providing a forum for the presentation of recent results and the exchange of ideas and experience in topics concerned with programming languages and systems. APLAS is based in Asia, but intends to be an international forum that serves the worldwide programming languages community. The APLAS series is sponsored by the Asian Association for Foundation of Software (AAFS), which has recently been founded by Asian researchers in cooperation with many researchers from Europe and the USA. APLAS has been discussed and prepared through informal workshops held in Singapore (2000), Daejeon (2001), and Shanghai (2002). APLAS03 will be the first formal symposium in the series. TOPICS: The symposium is devoted to foundational issues in programming languages and systems, covering the following areas: * semantics and theoretical foundations * type systems and language design * compilers and implementation * program analysis and security * program transformation and calculation * concurrency GENERAL CHAIR: Wei Li National Laboratory of Software Development Environment Beijing University of Aeronautics and Astronautics Beijing, 100083, China E-mail: liwei(a)nlsde.buaa.edu.cn PROGRAM CHAIR: Atsushi Ohori (http://www.jaist.ac.jp/~ohori) School of Information Science Japan Advanced Institute of Science and Technology Tatsunokuchi, Ishikawa, 923-1292 JAPAN E-mail: ohori(a)jaist.ac.jp Tel: +81 761 51 1275, Fax: +81 761 51 1149 PROGRAM COMMITTEE: * Manuel Chakravarty (University of New South Wales, Australia) * Wei Ngan Chin (National University of Singapore, Singapore) * Tyng-Ruey Chuang (Academia Sinica, Taiwan) * Yuxi Fu (Shanghai Jiaotong University, China) * Masahito Hasegawa (Kyoto University, Japan) * Kohei Honda (Queen Mary College, UK) * Zhenjiang Hu (University of Tokyo, Japan) * Peter Lee (Carnegie Mellon University, USA) * Shilong Ma (Beijing University of Aeronautics and Astronautics, China) * Martin Odersky (Ecole Polytechnique de Lausanne, Switzerland) * Atsushi Ohori (JAIST, Japan), Chair * Don Sannella (University of Edinburgh, UK) * Zhong Shao (Yale University, USA) * Kwangkeun Yi (KAIST, Korea) * Taiichi Yuasa (Kyoto University, Japan) IMPORTANT DATES: Submission deadline: May 27, 2003 Notification of acceptance: July 17, 2003 Final paper due: August 17, 2003 Symposium: October 27-29, 2003 PROCEEDINGS AND SUBMISSION PROCEDURE: The proceedings will be published in the Springer-Verlag Lecture Notes in Computer Science series. Final papers will be no more than *15* pages long in the format specified by Springer-Verlag at the URL: http://www.springer.de/comp/lncs/authors.html Prospective authors are invited to submit a 100-200 word abstract and a full paper in English presenting original research. Submitted papers must be unpublished and not submitted for publication elsewhere. Submissions will be carried out electronically via the Web via a link found at the symposium web page http://www.jaist.ac.jp/aplas/ Papers must be submitted in either PDF format, or as PostScript documents that are interpretable by Ghostscript. Those who have difficulty in web-based submission should contact the program chair before the deadline. It is recommended that submissions adhere to the format and length of the proceedings described above. Submissions that are clearly too long may be rejected immediately.

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default class methods in sub-classes
by Dylan Alex Simon 06 Feb '03

06 Feb '03

Apparently I can't do this (in ghc or hugs -- haven't tried others): class Space a where distance :: a -> a -> Int subtract :: a -> a -> a class (Space a) => NormSpace a where norm :: a -> Int distance a b = norm (subtract a b) That is, I can't make (or redefine) a default for the superclass method 'distance' in a subclass. I agree that the Haskell'98 definition doesn't claim that this should be allowed, but it seems like something that would be useful. Are there reasons not to allow this (or that I shouldn't want to do this at all)? Apologies if this is well-covered. I couldn't find any mention of it. :-Dylan Simon

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ICFP 2003 CFP -- minor but critical correction
by Olin Shivers 06 Feb '03

06 Feb '03

The submission date, March 29, is a Saturday, *not* a Thursday. Sorry 'bout that. -Olin =============================================================================== Eighth Annual ACM SIGPLAN International Conference on Functional Programming ICFP 2003 Call for Papers (Revised 2003/2/5) Affiliated with PLI 2003 August 25-29, 2003 Uppsala, Sweden http://www-users.cs.york.ac.uk/~colin/icfp2003.html http://www.cc.gatech.edu/icfp03/cfp.html ------------------------------------------------------------------------------- * Important dates ----------------- Submission deadline 18:00 EST 29 March, 2003 (Saturday) Notification of acceptance rejection 19 May, 2003 Final paper due 16 June, 2003 Conference 25-29 August, 2003 * Scope ------- ICFP 2003 seeks original papers on the full spectrum of the art, science, and practice of functional programming. The conference invites submissions on all topics ranging from principles to practice, from foundations to features, and from abstraction to application. The scope covers all languages that encourage programming with functions, including both purely applicative and imperative languages, as well as languages that support objects and concurrency. Topics of interest include, but are not limited to, the following: Foundations formal semantics, lambda calculus, type theory, monads, continuations, control, state, effects. Design Algorithms and data structures, modules and type systems, concurrency and distribution, components and composition, relations to object-oriented and logic programming, multiparadigm programming. Implementation abstract machines, compile-time and run-time optimization, just-in-time compilers, memory management. Interfaces to foreign functions, services, components and low-level machine resources. Transformation and analysis abstract interpretation, partial evaluation, program transformation, theorem proving, specification and verification. Software development techniques for functional programming design patterns, specification, verification and validation, debugging, test generation, tracing and profiling. Applications and domain-specific languages systems programming, scientific and numerical computing, symbolic computing and artificial intelligence, systems programming, databases, graphical user interfaces, multimedia programming, application scripting, system administration, distributed-systems construction, web programming. Practice and experience functional programming in education and industry, ramifications on other paradigms and computing disciplines. Functional pearls elegant, instructive examples of functional programming. Papers in the latter three categories need not necessarily report original research results; they may instead, for example, report practical experience that will be useful to others, re-usable programming idioms, or elegant new ways of approaching a problem. The key criterion for such a paper is that it makes a contribution from which other practitioners can benefit. It is not enough simply to describe a program! * Submission guidelines ----------------------- Due date & time: Submissions must be filed at the web site by 18:00 EST on Saturday 29 March. Some convenient equivalents to 18:00 EST are New York: 6:00 PM = 18h00 San Francisco: 3:00 PM = 15h00 Chicago: 5:00 PM = 17h00 Paris: Midnight Hong Kong: 7:00 AM (30 March) UTC: 2300 For other time-zones/locations, see http://www.timeanddate.com/worldclock/fixedtime.html Submission URL: http://www.cc.gatech.edu/icfp03/submit Authors should submit a 100-200 word abstract and a full paper by 23:00 Universal Coordinated Time on Saturday, 29 March, 2003. Submissions should be no more than 12 pages (including bibliography and appendices) in standard ACM conference format: two columns, nine-point font on a ten-point baseline, with pages 20pc (3.33in) wide and 54pc (9in) tall, with a column gutter of 2pc (0.33in). Detailed formatting guidelines are available at http://www.acm.org/sigs/pubs/proceed/template.html, along with formatting templates or style files for LaTeX, Word Perfect, and Word. You don't need to include categories, keywords, etc., though you are welcome to do so. Also, note that the ACM copyright notice is not required of submissions, only of accepted papers. Authors wishing to supply additional material to the reviewers beyond the 12-page limit can do so in clearly marked appendices, on the understanding that reviewers are not required to read the appendices. Submissions that do not meet these guidelines will not be considered. The submission deadline and length above are firm. Submissions will be carried out electronically via the Web, at the URL given above. Papers must be submitted in either PDF format, or as PostScript documents that are interpretable by Ghostscript, and they must be printable on US Letter sized paper. Individuals for which this requirement is a hardship should contact the program chair at least one week before the deadline. Submitted papers must have content that has not previously been published in other conferences or refereed venues; simultaneous submission to other conferences or refereed venues is unacceptable. Each paper should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, saying why it is significant, and comparing it with previous work. Authors should strive to make the technical content of their papers understandable to a broad audience. Authors of accepted papers will be required to sign the ACM copyright form. Proceedings will be published by ACM Press. * Student Attendees ------------------- Students who have a paper accepted for the conference are offered student membership of SIGPLAN free for one year. As members of SIGPLAN they may apply for travel fellowships from the PAC fund. * Conference Chair ------------------ Colin Runciman University of York, UK * Program Chair --------------- Olin Shivers College of Computing Georgia Institute of Technology Atlanta, Ga. 30332-0280, USA shivers at cc.gatech.edu Phone: +1 404 385.00.91 Fax: +1 404 383.12.53 * Program Committee ------------------- Andrzej Filinksi (DIKU, University of Copenhagen) Robby Findler (University of Chicago) Fritz Henglein (IT University of Copenhagen) Hugo Herbelin (INRIA) Ralf Hinze (Universitat Bonn) Annie Liu (Stony Brook University) Benjamin Pierce (University of Pennsylvania) Todd Proebsting (Microsoft Corp.) Amr Sabry (University of Indiana) Zhong Shao (Yale University) Tim Sheard (OGI School of Science and Engineering) Eijiro Sumii (University of Tokyo) * Change log ------------ 2003/2/5 Added program committee; revised submission deadline from 3/20 to 3/29; updated student travel-fellowship information. 2003/2/5 March 29 is Saturday, not Thursday. (March 20 is a Thursday.)

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Re: Looking for large Haskell programs
by George Russell 06 Feb '03

06 Feb '03

Tobias Gedell wrote > I'm looking for large haskell programs with more than 15000 lines of > code. Does any of you know where I can find such programs? The programs > found in the nofib suite are not large enough. The UniForM workbench is currently almost 80000 lines (of which 4500 are actually HaXml, so don't really count), and is almost all Haskell. It uses a lot of Glasgow extensions though.

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