- Haskell - Haskell.org

I need some help
by Bahadır SEVİNÇ 26 Mar '02

26 Mar '02

Hello I am writing a whole program which is analyz a elegtromagnetic wave. This is ok but in the program I use a lot of constant for example pi,epsilon etc. I want to ask that how I use a constant in Haskell ? However the user of the program give some argument then program is starting. And I want to use this arguments for example at the end of the program. What will I do. Thanks Baha Electrical & Electronics Engineer Bahadır SEVİNÇ Fırat University Informatics Department & Computer Center Elazığ / Türkiye 23169 Tlf: +90 424 2370000-5011

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instance Read Dynamic ?
by Dean Herington 25 Mar '02

25 Mar '02

The type `Dynamic` is an instance of `Show` but not of `Read`. Is there some reason `Dynamic` could not be made an instance of `Read`? Has anyone extended `Dynamic` in that way? Dean Herington

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ITRS'02 call for papers
by Steffen van Bakel 25 Mar '02

25 Mar '02

(Apologies for multiple copies) (Second) Call for Papers Workshop on Intersection Types and Related Systems (ITRS '02) Copenhagen, Denmark Friday, July 26 2002 http://www.doc.ic.ac.uk/~itrs02/ Co-located with FLoC '02, the third Federated Logic Conference to be held in Copenhagen, Denmark (July 22 to August 1 2002) http://floc02.diku.dk/ IMPORTANT DATES/DEADLINES: Submission of papers: Sunday, April 7 2002 Notification of acceptance: Thursday, April 25 2002 Workshop: Friday, July 26 2002 OVERALL TOPIC AND FORMAT OF WORKSHOP: Intersection type disciplines originated in 1980 to overcome the limitations of Curry's type assignment system and to provide a characterisation of the strongly normalising terms of the Lambda Calculus. Since then, intersection types disciplines were used in a series of papers for characterising evaluation properties and semantics. Types also support reliable reasoning in many areas such as logic, programming languages, linguistics, etc. A _polymorphic_ type stands for some number of instance types, and the use of type systems for non-trivial purposes generally requires polymorphic types. In this context, roughly speaking, intersection types could be seen as to provide type polymorphism by listing type instances. This differs from the more widely used ("forall") quantified types, which provide type polymorphism by giving a type scheme that can be instantiated into various type instances. (A similar relationship holds between union types and existential types, the duals of intersection types and universal types.) Although intersection types were initially intended for use in analyzing and/or synthesizing lambda models as well as in analyzing normalization properties, over the last twenty years the scope of theoretical research on intersection types has broadened. Recently, there have been a number of breakthroughs in the use of intersection types (and similar technology) for practical purposes such as program analysis. The ITRS '02 workshop will be held to bring together researchers working on both the theory and practice of systems with intersection types and related systems (e.g., union types, refinement types, etc.). The workshop will last one full day and will contain a long talk by each invited speaker, a panel discussion, and a short (approx. 25 minutes) talk for each accepted paper. POSSIBLE TOPICS FOR SUBMITTED PAPERS: Researchers are invited to submit original papers on topics in the spirit of the workshop. Possible topics for submitted papers include, but are not limited to: * Formal properties of systems with intersection types: principal typings, normalization properties (for normal forms, head-normal forms, weak head-normal forms, etc.), type inference algorithms. * Results for clearly related systems, e.g., systems with union types, refinement types, or singleton types. * Connections with not-so-clearly related approaches such as abstract interpretation and constraints. * Applications to lambda calculus and similar systems, e.g., denotational semantics, analysis/synthesis of lambda models (domains), characterization of operational properties, etc. * Applications for programming languages, e.g., program analysis (flow, strictness, totality, etc.), accurate type error messages, increased flexibility with static typing, separate compilation and modularity, optimizing transformations, types for objects, etc. * Applications for other areas, e.g., database query languages, program extraction from proofs, type systems for natural languages. INVITED SPEAKER (confirmed) Frank Pfenning (Carnegie Mellon University, USA) REGISTRATION FEE 50 Euro for the workshop; an additional 80 Euro will be charged to participants who haven't registered for one of the main FLoC conferences (but only once, not per workshop) PROGRAM COMMITTEE: Steffen van Bakel (Chair) (Imperial College, London, UK) Franco Barbanera (Universita` di Catania, Italia) Mario Coppo (Universita` di Torino, Italia) Luca Roversi (Universita` di Torino, Italia) Lyn Turbak (Wellesley College (MA) USA) Pawel Urzyczyn (Uniwersytet Warszawski, Polska) Joe Wells (Heriot-Watt University, Edinburgh, Scotland) SUBMISSION INSTRUCTIONS: TOPIC: A submitted paper must describe work that does not substantially overlap with work that has been previously published or is currently being considered elsewhere (e.g., another workshop, conference, or journal). Feel free to consult the program chair on the appropriateness of a topic or the possibility of conflict with another publication. PRINTED APPEARANCE: The paper must be written in English. The paper (including bibliography) should not exceed 15 pages. The paper should a font size no smaller than 11pt and standard TeX spacing. It is recommended to include full proofs of any theorems in appendices if they will not fit in 15 pages. However, any appendices beyond the 15-page limit should not be needed for judging the paper and will not be included in the proceedings. PAPER ELECTRONIC FORMAT: The paper should be in PostScript or PDF. Every effort should be made to ensure that only portable PostScript features are used (e.g., avoid using non-standard built-in fonts). For other formats, ask the program chair well in advance of the deadline. For TeX, the class file itrspaper.cls is recommended for use (available at http://www.doc.ic.ac.uk/~itrs02/itrspaper.cls) ADMINISTRATIVE INFORMATION: The first page of the paper should include (1) the title, (2) the list of authors, (3) a brief abstract (fewer than 200 words), (4) a short list of key words/topics, and (5) the name, e-mail address, and postal address of the corresponding author. This information should be repeated at the Paper Submission Page available at the workshop's website = (http://www.doc.ic.ac.uk/~itrs02/) SUBMISSION: Papers can be submitted electronically via the Paper Submission Page available at the workshop's website = (http://www.doc.ic.ac.uk/~itrs02/) VENUE: The workshop is colocated with the FLoC '02 conference, which will be held in Copenhagen, Denmark. CONTACT INFORMATION: Web: http://www.doc.ic.ac.uk/~itrs02/ Program chair: Steffen van Bakel e-mail: itrs02@doc.ic.ac..uk telephone: +44 20 7495 8263 fax: +44 20 7581 8024 postal: Department of Computing Imperial College 180 Queens's Gate London SW7 2BZ, UK

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Announce: Gtk2Hs - A Haskell binding for Gtk2
by Axel Simon 25 Mar '02

25 Mar '02

Note: This is not gtk+hs. Gtk2Hs is a rewrite of gtk+hs. It is a binding to the recently released version of Gtk2 with a couple of improvements over gtk+hs: - Automatic memory management. - Nearly complete coverage of widget functions and their signals, including the new text and list widgets. - The convenience wrapper MoGuL (Monad Gui Library) makes it possible to create and lookup named widgets in a type safe way. - Unicode support. - Object-oriented calling convention for widget functions. - Pragmatically uses both c2hs and hsc acquire information about the C files. Automatically generates callback handlers and the widget type hierarchy. - Needs ghc version 5.00 or later, makes use of the --make flag and complies quite quickly (12 mins). I am currently only providing CVS access to the sources. Find them at: https://sourceforge.net/cvs/?group_id=49207 At the moment it does not compile on Solaris due to the 4 parameter restriction of GHC for dynamic callbacks. Feedback is very welcome, a good place to send it to is: gtk2hs-users(a)lists.sourceforge.net Share and enjoy, Axel.

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http://haskell.org
by Christine Hall 24 Mar '02

24 Mar '02

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ANNOUNCE: Red Hat RPMs of Haskell Mode for Emacs
by Tom Moertel 22 Mar '02

22 Mar '02

I have packaged the Haskell Mode for Emacs at http://www.haskell.org/haskell-mode/ into RPMs for Red Hat Linux 7.2 (and similar platforms). Once the packages are installed, Haskell Mode is automatically enabled when you start up Emacs. Integration with Hugs is the default, but a quick change to your .emacs file will cause Haskell Mode to use GHCi instead. You can find the RPMs here: http://www.moertel.com/~thor/emacs-haskell-mode/ Cheers, Tom P.S. I have also made the RPM .spec file available. If somebody can add it to the official haskell-mode tarball on haskell.org, people can build RPMs directly from the tarball using "rpm -ta haskell-mode-(VERS).tar.gz".

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Haskell server switchover
by Mark Wogahn 22 Mar '02

22 Mar '02

Hi All, I will be bringing the haskell server down tomorrow morning (Sat Mar 23 ) between 08:00 and 8:30 to do some needed service. It should be back online no later than 9:00. Sorry for any inconvenience. -Mark -- Mark Wogahn / mark.wogahn(a)yale.edu Workstation Support Services (WSS) Department of Computer Science 51 Prospect Street, New Haven, CT 06520 Phone: (203) 432-1264 Fax: (203) 432-0593 -------------------------------------------------------- "Nothing is static, everything is falling apart" Chuck Palahniuk - "Fight Club"

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Hugs Bug !
by Ahn Ki-yung 22 Mar '02

22 Mar '02

Prelude> f 1 where f x = x : f x [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, ,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, ,1,1,{Interrupted!} Prelude> f 1 where f x = x : f x ==================== in unix/linux proper error msg comes out and back to interpreter. ERROR - Control stack overflow =========== but in windows 2000 Then suddnly interpreter fails and the red (X) popup window pops up. hugs.exe - application programm error unknown software exception (0xc000fd) ... blabla

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RE: catch (fail "...")
by Simon Peyton-Jones 22 Mar '02

22 Mar '02

This is an inconsistency that was fixed in the revised Haskell98 report (Apr 2001). See http://research.microsoft.com/~simonpj/haskell98-revised In the bug list look for Page 90. It looks as though Hugs hasn't quite caught up with this change. Simon | -----Original Message----- | From: Brian Huffman [mailto:bhuffman@galois.com] | Sent: 22 March 2002 00:22 | To: haskell(a)haskell.org | Subject: catch (fail "...") | | | Hi, | | Here is a problem I came across recently, revealing a | difference between ghci | and Hugs: | | hugs> catch (error "not ok") (\e -> putStrLn "ok") | Program error: not ok | ghci> catch (error "not ok") (\e -> putStrLn "ok") | *** Exception: not ok | | hugs> catch (ioError (userError "not ok")) (\e -> putStrLn "ok") | ok | ghci> catch (ioError (userError "not ok")) (\e -> putStrLn "ok") | ok | | hugs> catch (fail "not ok") (\e -> putStrLn "ok") | Program error: not ok | ghci> catch (fail "not ok") (\e -> putStrLn "ok") | ok | | As I expected, neither of them can catch "error", and both of | them can catch | "ioError". But only ghci can catch the "fail". It seems to me | that ghc has | made a convenient choice here, because if I need to raise an | IO exception, it | is easier to type "fail s" than "ioError (userError s)". | | However, the online Haskell report says that for IO, fail s = | error s, which | is what Hugs does. | (http://www.haskell.org/onlinereport/standard-prelude.html#$iM onad$$IO) Does anyone know the reasoning behind the design choice made in the report, or why the ghc implementation is different? I am mainly concerned about portability issues: particularly, is it a good idea to use fail for raising IO exceptions? Thanks - Brian Huffman _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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Lambda over types.
by anatoli 22 Mar '02

22 Mar '02

I apologise in case this doesn't make any sense. ghc -fglasgow-exts -fallow-undecidable-instances allows constructs which amount to lambda abstraction over types. I've written a small untyped lambda calculus interpreter in the Haskell class/instance sublanguage, just to prove this point. (The terms are Haskell *types*.) Using this interpreter as a basis, and adapting it as necessary, I can now write arbitrary "functions" [1] that take types to types. But of course it's a pain to write them like that. Maybe, after all, it does make sense to have a dedicated lambda-over-types Haskell extension which is convenient to use? [1] - I cannot produce an equivalent of > type Foo a b c = <some-function-over-types> a b c but I can do an equivalent of this: > fun :: T1 -> T2 -> T3 -> <some-function-over-types> T1 T2 T3 -- anatoli __________________________________________________ Do You Yahoo!? Yahoo! Movies - coverage of the 74th Academy Awards� http://movies.yahoo.com/

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