- Haskell - Haskell.org

ANNOUNCE: Chameleon version 02-11
by Martin Sulzmann 15 Nov '02

15 Nov '02

Chameleon is a Haskell-style language which provides a flexible overloading mechanism based on Constraint Handling Rules (CHRs). The latest version comes with a type debugger. Our approach handles Hindley/Milner types with Haskell style overloading (including advanced features such as functional dependencies etc.) For more details check out http://www.comp.nus.edu.sg/~sulzmann/chr/publications.html for papers describing Chameleon, http://www.comp.nus.edu.sg/~sulzmann/chameleon/ for the latest release including a number of examples. Cheers, Martin

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Time library underspecified
by Peter Thiemann 14 Nov '02

14 Nov '02

Did anyone try to use the standard Time library that comes with Haskell for a serious purpose? I wanted to, but came across the problem that the TimeDiff data type is underspecified. For example, what is the official way to convert a TimeDiff value into seconds? The problematic parts are: * how many days for one tdYear (365, 366) * how many days for one tdMonth (28,29,30,31) * how many seconds for one tdMin (given the presence of leap seconds)^(1) Actually, once the absolute reference of the TimeDiff is lost, then it is impossible to recover leap years and leap seconds, so TimeDiff better had to account for them somehow. I suppose, the best would be to just have diffClockTimes return the number of seconds as an Integer. Since Simon PJ has finished editing the library report, who's now in charge of keeping track of problems with it and perhaps writing a commentary in cases such as this? Cheers -Peter (1) for this one, there is reasonable consensus. for example the ISO 8601 standard (representation of dates and times) defines minute=60 seconds, hour=60 minutes, day=24 hours. However, this leads to the strange(?) situation that the difference between 1998-12-31T12:00:00 and 1999-01-01T12:00:00 is 1 day and one second. (There was a leap second on that night 1998 December 31 23h 59m 59s 1998 December 31 23h 59m 60s 1999 January 01 0h 0m 0s see http://tycho.usno.navy.mil/leap.html)

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Re: storing to a file
by Ferenc Wagner 14 Nov '02

14 Nov '02

Johan Steunenberg <johan.steunenberg(a)openknowledge.de> writes: > how to store a Double, or any non-char, to a file. I can give you a general advice: store it in ASCII format via show, unless you have *VERY* strong reasons against it. Yes, it results in bigger files (but you can compress them), and slower (what compression makes even worse) but you gain easy view/edit and compatibility. I couple of years ago I was very fond of binary formats... Feri.

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ANNOUNCE: rsa-haskell 1.0.0
by David Sankel 13 Nov '02

13 Nov '02

rsa-haskell 1.0.0 ================= This is an announcement for a version 1.0.0 of the rsa-haskell library/tools. Description: rsa-haskell is a haskell implementation of the RSA algorithm. It contains simple programs that are useful for encrypting/decrypting anything that can be piped from STDIN/STDOUT. rsa-haskell also has an easy-to-use rsa and number theory library. For more information and download: http://www.electronconsulting.com/rsa-haskell/ Please email comments, bugs, etc. to camio(a)yahoo.com. David J. Sankel __________________________________________________ Do you Yahoo!? U2 on LAUNCH - Exclusive greatest hits videos http://launch.yahoo.com/u2

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Report and web site
by Iavor S. Diatchki 12 Nov '02

12 Nov '02

hi, now that the report is pretty much stable, are there any plans of putting it on the Haskell web site? bye iavor -- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================

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HC&A Report: "Haskell 98 Report" copyright
by Ian Lynagh 12 Nov '02

12 Nov '02

Hi all, I note with some sadness the more restrictive license that may be placed on the "Haskell 98 Report", as reported by the HC&A. The great openness/freeness of haskell, both the report and implementations, is, IMO, one of its most important features. I have just grabbed a copy of the latest revised report under the current licence. AIUI I can continue to publish this under the current licence and, assuming I change the name, incorporate any fixes etc (assuming the fixers agree to it). Also, Debian can continue to have a copy in main in the same way. I would really prefer it if such forking wasn't necessary, but if the above is the case (I am not a lawyer, etc etc) then I guess it isn't the end of the world - I must admit to not seeing what CUP would be getting out of it if this is so, though. Ian

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ANNOUNCE: HC&A Report (3rd edition, November 2002)
by C.Reinke 11 Nov '02

11 Nov '02

The many contributors and I are happy to announce that the Haskell Communities and Activities Report (3rd edition, November 2002) http://www.haskell.org/communities/ is now available from the Haskell Communities home page in several formats: in PDF (with working links and index, yet printable) or, for those who have problems with the PDF, in HTML (using John's secret weapon again) and Postscript. A big thanks here to everyone who contributed information to the report! I hope you will find it as interesting to read as we did. For those of you who haven't heard of these reports before: The first edition of the HC&A Report was released in November 2001, with the goal of helping to improve the communication between the various groups, projects, and individuals working on or with Haskell. The idea of these reports is simple: Every six months, a call goes out to all of you to contribute brief summaries of your own area of work. Many of you respond (eagerly, unprompted, and well in time for the deadline;-) to the call. I then collect all these into a single report and feed it back to this very mailing list. And when we try for the next update in six months, you might want to add your own work, project, research area or group as well. So, please, put that item into your diary now: End of April 2003: target deadline for contributions to the May 2003 edition of the HC&A Report Enjoy (and communicate;-)! Claus Reinke -- Computing Laboratory University of Kent at Canterbury http://www.cs.ukc.ac.uk/people/staff/cr3/

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New Strafunski packages released
by Ralf Laemmel 10 Nov '02

10 Nov '02

New Strafunski packages released -------------------------------- Strafunski is a Haskell-centred bundle that provides support for generic programming and language processing. Strafunski is based on the notion of a functional strategy --- first-class generic functions that can traverse into terms while mixing uniform and type-specific behaviour. This is the 3rd release of Strafunski with the following improvements: - StrategyLib extended by several themes, e.g., for metrics. - Added Sdf2Haskell package for mapping syntaxes to datatypes. - Cobol, Java, and Haskell meta-programming examples included. - Haskell ATermLib integrated. - Sample code from the following papers integrated: - PADL 2003: A Strafunski application letter - RULE 2002: Towards Generic Refactoring - WRS 2002: The Sketch of a Polymorphic Symphony - DrIFT-Strafunski supports a number of additional models. Documentation, papers, and downloads are now available from: http://www.cs.vu.nl/Strafunski A good entry point for contemporary Strafunski is: A Strafunski Application Letter (PADL 2003) See http://www.cwi.nl/~ralf/padl03/ It demonstrate that typed functional programming in Haskell, augmented with Strafunski's support for generic traversal and external components, is very appropriate for the development of practical language processors. In particular, Strafunski is used for Cobol reverse engineering, Java code metrics, and Haskell re-engineering. Feedback is very much appreciated, and can be directed to the authors: * Ralf Laemmel (ralf(a)cwi.nl) * Joost Visser (Joost.Visser(a)cwi.nl) Have fun!

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Announcement: Alex has a new home
by Chris Dornan 10 Nov '02

10 Nov '02

Announcement: Alex under new license and management. Alex, the Haskell-based scanner-generator, has been relicensed with a BSD-style license (it was under the GPL) in preparation for integration with Happy, the Haskell-based parser generator. Isaac Jones has kindly and heroically undertaken this task of integrating the two packages. As the two packages work quite well as they are it is expected that the first release of the combined packages will do little more than bundle them together, but we have ambitions to go further, and to better adapt the run-time behaviour of Alex-generated scanners to suit the big Haskell compilers such as GHC. Until the integration has been completed the new home for Alex is http://www.syntaxpolice.org/~ijones/alex/ Please email Isaac (ijones(a)syntaxpolice.org) if you have any queries. Cheers, Chris Dornan cdornan(a)arm.com

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want better error msg with Class Read
by Johannes Waldmann 07 Nov '02

07 Nov '02

Dear all, I would welcome some advice on getting better error messages when using read :: Read a => a The problem is, `readsPrec' (the class method) eats the longest feasible input prefix, but when I call `read' (built-in prelude function) on a string that does not parse, but that has a valid prefix, I get this: > Inter> readsPrec 0 "1 ) " :: [(Integer,String)] > [(1," ) ")] > Inter> read "1 )" :: Integer > > Program error: Prelude.read: no parse This is correct, but I would like to show (in the error message) the prefix that *was* parsed as well. If `read' was a class method, I could override it. (Compare class Show, where there is the method `showsPrec', but since H98 (?), `show' is a class method as well.) In my application, the type to parse is not Integer, but some expression type that might contain parentheses. Its Read instance uses the Parsec library, but I think this is irrelevant to the above question. Best regards, -- -- Johannes Waldmann ---- http://www.informatik.uni-leipzig.de/~joe/ -- -- joe(a)informatik.uni-leipzig.de -- phone/fax (+49) 341 9732 204/207 --

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