January 2002 - Haskell

Re: question about kinds
by Ashley Yakeley 19 Jan '02

19 Jan '02

At 2002-01-18 13:10, Hal Daume III wrote: >Now, I want to say that if some data type 'd' is Traversable and another >data type 'e' is Traversable, then the "combined data type" is >Traversable. That is, for example, I want to say that a Tree of Lists is >traversable, or that a List of Trees, or a List of Lists is traversable. If the Tree type constructor is Traversable, then it's Traversable no matter what it's applied to. You've provided a instance for traversing "Trees of anything", it's going to overlap with any instance for "Trees of Lists". -- Ashley Yakeley, Seattle WA

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Re: dependent type query
by Ashley Yakeley 19 Jan '02

19 Jan '02

At 2002-01-18 12:01, Hal Daume III wrote: >class MyClass f a | a -> f, f -> a where ... > >I want to write a data type: > >data (MyClass f a) => MyData f = MyData (f, a) > >But this doesn't seem to be valid because "a" isn't in scope. Class constraints in 'data' declarations only affect the type of constructor functions. In other words, data (Context) => MyData a b c = MkMyData whatever is equivalent to data MyData a b c = MkMyData whatever except for the type of MkMyData, which will be MkMyData :: (Context) => whatever -> MyData a b c instead of MkMyData :: whatever -> MyData a b c > But a is uniquely determined by f. What gives? What you want is data MyData f = forall a. (MyClass f a) => MyData (f, a) >Furthermore, I can't even write: > >data (MyClass f a) => MyData2 f = MyData2 f Well now this is odd. I had no trouble simulating it with this: data MyData2 f = MyData2 f mkMyData2 :: (MyClass f a) => f -> MyData2 f mkMyData2 = MyData2 Looks like extended Haskell is being excessively restricted. Comments? -- Ashley Yakeley, Seattle WA

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dependent type query
by Hal Daume III 18 Jan '02

18 Jan '02

Suppose I have the following definition: class MyClass f a | a -> f, f -> a where ... I want to write a data type: data (MyClass f a) => MyData f = MyData (f, a) But this doesn't seem to be valid because "a" isn't in scope. But a is uniquely determined by f. What gives? Furthermore, I can't even write: data (MyClass f a) => MyData2 f = MyData2 f This makes no sense to me whatsoever. This problem can the thwarted by moving the contraint to only the function definitions, but for MyData itself, it's really a hassle. Please could someone explain what's going on? -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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RE: (no subject)
by Simon Peyton-Jones 18 Jan '02

18 Jan '02

Perfectly sensible suggestion, but too late for the H98 Report, I'm afraid. It's time to freeze it. Simon | -----Original Message----- | From: D.Wakeling(a)exeter.ac.uk [mailto:D.Wakeling@exeter.ac.uk] | Sent: 08 January 2002 10:02 | To: haskell(a)haskell.org | Subject: (no subject) | | | | Hello, | | Is there any reason why the "gap" in a string literal is defined as | | gap -> \whitechar {whitechar}\ | | (in Section 2.6 of the report), rather than | | gap -> \whitespace\ | | ? The second, more liberal, definition of "gap" seems more | natural. Moreover, it would allow comments in the gaps, which | I would find useful. For example, | | classHeader :: String | classHeader = "\xca\xfe\xba\xbe\ -- magic number | \\x00\x03\ -- minor version | \\x00\x2d" -- major version | | David | -------------------------------------------------------------- | ----------------- | Dr. David Wakeling, School of Engineering and Computer Science | University of Exeter, Exeter, Devon, EX4 4PT. | unofficial web page: http://www.dcs.ex.ac.uk/~david | -------------------------------------------------------------- | ----------------- | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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RE: Unicode again
by Simon Peyton-Jones 18 Jan '02

18 Jan '02

| there was some discussion about Unicode and the Char type | some time ago. At the moment I'm writing some Haskell code | dealing with XML. The problem is that there seems to be no | consensus concerning Char so that it is difficult for me to | deal with the XML unicode issues appropriately. Is there any | option that is very likely to get into the Haskell report? There was an extended discussion on the Haskell mailing list about Unicode and the Haskell report, which you can find in the mailling list archives. So far as Haskell 98 is concerned, the conclusion seems to be that there is no prospect of H98 handling Unicode "properly", so the report should avoid making premature commitments that would limit a future design. Check out the current draft at http://research.microsoft.com/~simonpj/haskell98-revised I'm very ignorant of Unicode, but maybe the others on the mailing list who contributed to the discussion can amplify. In any case, I am not going to make significant changes to the H98 Report at this stage, I'm afraid. Simon

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rank x polymorphism
by Hal Daume III 17 Jan '02

17 Jan '02

i'm familiar with ranks 1 and 2 of polymorphism. what are the higher ones (are there any). is there a good summary anywhere? -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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[E-CFP] WFLP2002 - Preliminary Call for Papers
by Marco Comini 16 Jan '02

16 Jan '02

=============================================================================== CALL FOR PAPERS 11th International Workshop on Functional and (Constraint) Logic Programming Grado, Italy June 20 - 22, 2002 =============================================================================== GENERAL The international workshop on functional and (constraint) logic programming WFLP 2002 aims to bring together researchers interested in functional programming, (constraint) logic programming, as well as their integration. Recent edition of the workshop have been held in Kiel (Germany), Benicassim (Spain), Grenoble (France), Bad Honnef (Germany). This workshop aims to promote the cross-fertilizing exchange of ideas and experiences among researches and students from the different communities interested in the foundations, applications, software engineering techniques and combinations of high-level, declarative (constraint) programming languages and related areas. The technical program of the workshop will include invited talks, presentations of refereed papers and demo presentations. The WWW page of the workshop is: http://www.dimi.uniud.it/~wflp2002/ ------------------------------------------------------------------------------- TOPICS The topics of interest include (but are not limited to): * Functional programming * Logic programming * Constraint programming * Deductive databases * Extensions of declarative languages * Multi-paradigm declarative programming * Foundations, semantics, non-monotonic reasoning, dynamics * Parallelism, concurrency and narrowing * Program analysis, abstract interpretation * Program transformation, partial evaluation, meta-programming * Specification, verification, declarative debugging * Knowledge representation, machine learning * Declarative programming and software engineering * Implementation of declarative languages * Advanced programming environments and tools * Applications The primary focus is on new and original research results but submissions describing innovative products, prototypes under development or interesting experiments (e.g., benchmarks) are also encouraged. ------------------------------------------------------------------------------- IMPORTANT DATES Submission of papers: March 20, 2002 Notification of acceptance: April 28, 2002 Camera-ready papers: May 15, 2002 Workshop: June 20 - 22 , 2002 ------------------------------------------------------------------------------- SUBMISSION Authors are invited to submit an extended abstract (no longer than 10 pages including figures and references) or a system description (no longer than 3 pages) in postscript format (11pt) via email to wflp2002(a)dimi.uniud.it before March 20, 2002. Submissions should include the title, authors' names, affiliations, addresses, and e-mail. The proceedings with the full versions of all accepted contributions (no longer than 15 pages for regular contributions and 3 pages for system descriptions) will be published as a Technical Report of the University of Udine. A selection of the accepted papers will be considered for publication in the Electronic Proceedings of Theoretical Computer Science (Elsevier) after the workshop. ------------------------------------------------------------------------------- BEST NEWCOMER AWARD 0An award will be given to the best paper exclusively written by one or several young researchers who have not yet obtained their PhD degrees. Papers written in this category should be clearly marked "Student papers" in the submission. ------------------------------------------------------------------------------- PROGRAM The workshop will be a 3-day event including presentations of the accepted papers, system demos, and 2 INVITED TALKS (to be announced) ------------------------------------------------------------------------------- LOCATION WFLP 2002 will take place in Grado, Italy. Grado is an island located on the Adriatic coast in a beautiful lagoon. It is famous for its attractive beaches, for its Roman history, and for the pleasant middleuropean atmosphere. Venezia is 100 km away and Trieste is 60 km away. More details about the accommodation, traveling information, etc., will be available at the WFLP 2002 WWW page at http://www.dimi.uniud.it/~wflp2002/ ------------------------------------------------------------------------------- CONTACT WFLP 2002 Moreno Falaschi Dipartimento di Matematica e Informatica Università degli Studi di Udine Via delle Scienze, 206 33100 UDINE, Italy Phone: +39-0432-55-8472 or -8400 (Secr.) Fax: +39-0432-55-8499 Email: wflp2002(a)dimi.uniud.it WWW: http://www.dimi.uniud.it/~wflp2002/ ------------------------------------------------------------------------------- PROGRAM COMMITTEE Maria Alpuente (Technical University of Valencia) Sergio Antoy (Portland State University) Manuel Chakravarty (University of New South Wales, Sidney) Rachid Echahed (IMAG, Grenoble) Francois Fages (INRIA Rocquencourt) Moreno Falaschi (Univ. Udine, chair) Thom Fruewirth (LMU Munich) Robert Glück (Waseda Univ., Japan and DIKU, Denmark) Michael Hanus (CAU Kiel) Tetsuo Ida (University of Tsukuba) Helene Kirchner (Univ. Nancy) Herbert Kuchen (Univ. Muenster) Michael Maher (Loyola University Chicago) Juan Jose Moreno Navarro (UP Madrid) Ernesto Pimentel (Univ. Malaga) Mario Rodriguez-Artalejo (UC Madrid) ------------------------------------------------------------------------------- LOCAL ORGANIZING COMMITTEE Gianluca Amato Demis Ballis Marco Comini Luca Di Gaspero Agostino Dovier Moreno Falaschi Alicia Villanueva -------------------------------------------------------------------------------

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Unicode again
by Wolfgang Jeltsch 16 Jan '02

16 Jan '02

Hello, there was some discussion about Unicode and the Char type some time ago. At the moment I'm writing some Haskell code dealing with XML. The problem is that there seems to be no consensus concerning Char so that it is difficult for me to deal with the XML unicode issues appropriately. Is there any option that is very likely to get into the Haskell report? According to my memory the following were more or less propagated: (1) range '\x0000' to '\xFFFF'; UTF-16 is used (2) range '\x000000' to '\x10FFFF'; chars denote codepoints (3) range '\x00000000' to '\x7FFFFFFF'; chars denote codepoints GHC 5 seems to implement the second variant; Hugs still uses the poor range of '\x00' to '\xFF'. What does nhc98 do? My opinion is that using (1) is very, very bad. The name "Char" suggests that values of the type are characters (glyphs). Well, even when using (2) or (3) Char does not denote characters but codepoints, but this is closer to denoting chars than (1). And memory usage shouldn't be an issue - a concept beeing much better is IMO worth the higher memory use. I prefer (3) over (2) because there is the possibility of expansion of the Unicode character set in the future. Another solution would be to specify that the upper bound of Char is initially '\x10FFFF' and shall be adapted as Unicode evolves. Also, as already said by another person, we should introduce a package dealing with encoding and decoding of character strings to/from octet streams. The encoding used with character I/O must be specified. Any comments? Wolfgang

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XSLT, Perl, Haskell, & a word on language design
by Manuel M. T. Chakravarty 16 Jan '02

16 Jan '02

This article on Kuro5hin should be of interest: http://www.kuro5hin.org/?op=displaystory;sid=2002/1/15/1562/95011 As a text snippet to provoke you to actually follow the link, I have chosen, The really bad thing is that the designers of XSLT [1.0] made the language free of side effects but then failed to include fundamental support for basic functional programming idioms. Cheers, Manuel

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CFP: FLOPS 2002
by Zhenjiang Hu 16 Jan '02

16 Jan '02

We apologize, if you receive this message more than once. ********************************************************************* * * * CALL FOR PAPERS * * * * Sixth International Symposium on Functional and Logic Programming * * (FLOPS 2002) * * (Co-located with ACM SIGPLAN ASIA-PEPM 2002) * * * * University of Aizu, Aizu, Japan * * September 15--17, 2002 * * * * http://www.ipl.t.u-tokyo.ac.jp/FLOPS2002/ * * * ********************************************************************* Background ========== The symposium is a forum for research on all issues concerning functional programming and logic programming. In particular, it wants to stimulate the cross-fertilization as well as integration of the two paradigms. The symposium takes place about every 1.5 years in Japan. Previous FLOPS meetings were held in Fuji Susuno (1995), Shonan Village (1996), Kyoto(1998), Tsukuba (1999), and Tokyo (2001). Topics ====== The Sixth International Symposium on Functional and Logic Programming (FLOPS 2002) solicits original papers in all areas of functional and logic programming, including (but not limited to): * Language issues: language design and constructs, programming methodology, integration of paradigms, interfacing with other languages, type systems, constraints, concurrency and distributed computing * Foundations: semantics, rewrite systems and narrowing, type theory, proof systems * Implementation: compilation techniques, memory management, program analysis and transformation, partial evaluation, parallelism * Applications: case studies, real-world applications, graphical user interfaces, internet applications, database connection, formal methods and model checking Invited Speakers ================ Kokichi Futatsugi (JAIST, Japan) Peter Stuckey (University of Melbourne, Australia) Philip Wadler (Avaya Labs, USA) Submissions =========== Submissions must be unpublished and not submitted for publication elsewhere. Submissions should fall into one of the following two categories: 1. Regular research papers: they should describe new results and will be judged on originality, correctness and significance. 2. System descriptions: they should contain a link to a working system and will be judged on originality, usefulness and design. All submissions must be written in English. Regular research papers can be up to 15 proceedings pages long, system descriptions will be up to 4 pages long. Authors are strongly encouraged to use LaTeX2e and the Springer llncs class file, available at http://www.springer.de/comp/lncs/authors.html The title page should indicate the submission category. Regular research papers should be supported by proofs and/or experimental results. In case of lack of space, this supporting information should be made accessible otherwise (e.g. a link to a web page, or an appendix). Submission is Web-based. In order to submit a paper, authors should fill in the submission form available at http://www.ucm.es/info/flops2002/www/submit.html where more detailed instructions are given. If submission through the Web is not possible, five hard copies may be sent to Mario Rodriguez-Artalejo Universidad Complutense de Madrid Departamento de Sistemas Informaticos y Programacion Edificio Fac. Matematicas Av. Complutense s/n 28040 Madrid, Spain Publication and presentation of accepted contributions ====================================================== The Proceedings of FLOPS 2002 will be published by Springer Verlag in the LNCS series. They will be available at the conference. One author of each accepted contribution is expected to attend the Symposium in order to present it. Presentations of regular research papers will be scheduled for 30 minutes, including questions from the audience. System presentations will be scheduled for 15 minutes. Important Dates =============== Submission Deadline: March 1, 2002 Notification: May 21, 2002 Final Version: June 25, 2002 Symposium: September 15-17, 2002 Program Co-Chairs ================= Zhenjiang Hu University of Tokyo, Japan Mario Rodriguez-Artalejo Universidad Complutense, Madrid, Spain E-Mail: flops2002(a)ucm.es Program Committee ================= Maria Alpuente Technical University of Valencia, Spain Wei-Ngan Chin National University of Singapore, Singapore Pierre Deransart INRIA-Rocquencourt, France Moreno Falaschi University of Udine, Italy Michael Hanus University of Kiel, Germany Zhenjiang Hu (Co-Chair) University of Tokyo, Japan Jan Maluszynski Linkoeping University, Sweden Aart Middeldorp University of Tsukuba, Japan Gopalan Nadathur University of Minnesota, USA Susumu Nishimura Kyoto University, Japan Catuscia Palamidessi The Pennsylvania State University, USA Mario Rodriguez-Artalejo (Co-Chair) Universidad Complutense, Madrid, Spain Francesca Rossi University of Padova, Italy Harald Sondergaard The University of Melbourne, Australia Kazunori Ueda Waseda University, Japan Kwangkeun Yi KAIST, Korea Local Arrangements Chair ======================== Taro Suzuki University of Aizu, Japan Sponsors ======== Sponsored by: Japan Society of Software Science and Technology (JSSST), University of Aizu In cooperation with: Association for Logic Programming (ALP).

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