October 2003 - Haskell

CFP: LL3; Submission deadline Oct. 17
by Jeremy Hylton 09 Oct '03

09 Oct '03

Call for Presentations Lightweight Languages Workshop (LL3) http://ll3.ai.mit.edu/ November 8, 2003 Cambridge, Ma., USA The Lightweight Languages Workshop series focuses on programming languages, tools, and processes that are usable and useful. Lightweight languages have been an effective vehicle for introducing new features to mainstream programmers. We encourage presentations on topics of interest to the community of lightweight language users and designers. We prefer topics that will interest a broad audience. We do not require the presentation of novel research ideas. We are looking for abstracts of talks to be given at the workshop. Send abstracts to ll3-submit(a)ai.mit.edu. See the full call for proposals <http://ll3.ai.mit.edu/cfp.html> for suggested topics. Deadlines --------- Submissions: Oct. 17, 2003 Notification: Oct. 24, 2003 Program Committee ----------------- Ken Anderson, BBN (co-chair) Jeremy Hylton, Python Software Foundation (co-chair) Geoffrey Knauth, BAE Systems Shriram Krishnamurthi, Brown University Erik Meijer, Microsoft WebData Dan Sugalski, Perl Foundation Greg Sullivan, MIT CSAIL For more information, email ll3(a)ai.mit.edu.

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About Haskell Thread Model
by Yang, Qing 09 Oct '03

09 Oct '03

Hello, I am a new learner of Haskell and I am interested in Haskell's concurrent model. Can somebody give me a brief intro about Haskell's thread model, like how the use-level threads are mapped to kernel thread and what scheduling mechanism that Haskell uses, or point me to some links or documents that I can learn from. Thanks, Qing Yang qing.yang(a)intel.com

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Haskell on the cover of a magazine!
by Daan Leijen 09 Oct '03

09 Oct '03

wxHaskell gets a two-page article in the october edition of the popular French PC magazine, L'Informaticien. The article is written by Frédéric Mazué, and gives an overview of wxWindows, wxHaskell, and compares the library against F# (the OCaml integration to .NET). For screenshots of the relevant pages, see: http://wxhaskell.sourceforge.net/screenshots.html#linformaticien Just think of all those thousands of French O'Caml programmers that will suddenly start to use Haskell ;-) All the best, Daan Leijen. "wxHaskell est un outil d'ores et déjà remarquable et d'une grande fiabilité. Examinons de plus près ce dont il s'agit." "En raison de toutes ses qualités, la popularité de Haskell va donc croissant"

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non blocking System.system?
by John Meacham 08 Oct '03

08 Oct '03

I was curious if there was a version of System.system floating about which doesn't block all threads when doing concurrency? just doing an actual fork and exec isn't sufficient because I need to do haskell things (like write to MVars) after the spawned app finishes. I imagine this might be written by catching sigCHLD and writing to an mvar, but I can't seem to get at the siginfo_t structure from the haskell signal callback to find out the pid of the process which died. John -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john(a)foo.net ---------------------------------------------------------------------------

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Fwd: non blocking System.system?
by r2yang＠engmail.uwaterloo.ca 08 Oct '03

08 Oct '03

I don't know what happened, but it seems some e-mails go in my address which should direct to haskell mailing list. rui ----- Forwarded message from John Meacham <john(a)repetae.net> ----- Date: Wed, 8 Oct 2003 14:02:46 -0700 From: John Meacham <john(a)repetae.net> Reply-To: John Meacham <john(a)repetae.net> Subject: non blocking System.system? To: haskell(a)haskell.org I was curious if there was a version of System.system floating about which doesn't block all threads when doing concurrency? just doing an actual fork and exec isn't sufficient because I need to do haskell things (like write to MVars) after the spawned app finishes. I imagine this might be written by catching sigCHLD and writing to an mvar, but I can't seem to get at the siginfo_t structure from the haskell signal callback to find out the pid of the process which died. John -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john(a)foo.net --------------------------------------------------------------------------- _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell ----- End forwarded message ----- ---------------------------------------- This mail sent through www.mywaterloo.ca

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constructor name clashes
by Ben_Yu＠asc.aon.com 08 Oct '03

08 Oct '03

Hi, all. I'm a newbie to Haskell so please bear with me if my questions sound silly. In coding Haskell, I feel very inconvenient that the name of data constructors for different types have to be different. Also, when declaring named fields of a type, such as data Data1 = Data1{ok1::Bool} data Data2 = Data2{ok2::Bool} the field names for different type also have to be unique. Isn't that annoying? Keeping all the names unique is no easy task in my opinion. Wouldn't it be nice if we can have something similar to structure fields in C? Or maybe this is already present and I'm just being ignorant? I know that we can use modules to introduce name spaces. But still, this is quite cumbersome. Thanks! Ben. This message is intended only for the addressee and may contain information that is confidential or privileged. Unauthorized use is strictly prohibited and may be unlawful. If you are not the intended recipient, or the person responsible for delivering to the intended recipient, you should not read, copy, disclose or otherwise use this message, except for the purpose of delivery to the addressee. If you have received this email in error, please delete and advise us immediately.

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haskell bindings for cairo
by Abraham Egnor 07 Oct '03

07 Oct '03

I've hacked together a haskell binding for the cairo vector graphics library (http://www.cairographics.org) It's still got much that needs improvement, but it's at the usable stage. A tarball is available at http://ofb.net/~abe/hscairo-0.1.tar.bz2 ; documentation and build instructions are included. Abe

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implement hash table
by r2yang＠engmail.uwaterloo.ca 07 Oct '03

07 Oct '03

Hi,all I'm a new one in this Haskell programming language. I have a program which involved a lot of computation tasks and it's quite inefficient,so I'm currently examing the possibility of using hash table in my data structure, can some one tell me how to implement it? I can't find much information about it. Thanks a lot Rui ---------------------------------------- This mail sent through www.mywaterloo.ca

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RE: Imported instance declarations
by Simon Peyton-Jones 06 Oct '03

06 Oct '03

This bad error message is improved in subsequent versions of GHC. 6.0.1 says In.hs:5: Duplicate instance declarations: In.hs:5: Functor ((->) i) In module Control.Monad.Reader: Functor ((->) r) Simon | -----Original Message----- | From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Frieder Kalisch | Sent: 01 October 2003 15:12 | To: haskell(a)haskell.org | Subject: Imported instance declarations | | Hello, | | While trying to learn Hakell I came across a weird (to me) error message | concerning imported instance declarations. | | This module | | module XXX() where | | import Control.Monad.Error() | | instance Functor ((->)i) where | fmap = (.) | | gives this error message (compiling with ghc 5.0.4.2): | | Duplicate instance declarations: | XXX.hs:5: Functor ((->) i) | <No locn>: Functor ((->) r) | | For me this error message is somewhat puzzling: Where is the second | instance declaration given? In this case it happens to be in | Control.Monad.Reader, but how can I find out without looking for it | in the CVS repository? The documentation for Control.Monad.Error does | not mention the imported modules. | | I suppose, that the compiler knows in which module the instance | declaration was given, because it needs to tell duplicate import paths | from duplicate instance declarations. Why is it not given in this example? | | Greetings | | Frieder Kalisch | | | -- | Frieder Kalisch | f.kalisch(a)tphys.uni-heidelberg.de | +49-6221-549-432 | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell

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ANNOUNCE: HaRe, the Haskell Refactorer, version 0.1
by C.Reinke 05 Oct '03

05 Oct '03

Dear Haskellers, as part of our project on Refactoring Functional Programs http://www.cs.kent.ac.uk/projects/refactor-fp/ we are pleased to announce the availability of HaRe 0.1 (also known as HaRe 01/10/2003 ;-), a snapshot of our Haskell Refactorer prototype. You can get it via http://www.cs.kent.ac.uk/projects/refactor-fp/hare.html Please see the README.txt for build/use instructions and known issues, and let us know about any problems, bugs, suggestions, or additional platforms you can confirm as working: our project address at kent.ac.uk is refactor-fp (which we'd like to keep spam-free). An initial catalogue describing the refactorings implemented in HaRe (with slightly different names) is included in the doc/ directory. Happy Refactoring! The HaRe Team (Huiqing Li, Claus Reinke, Simon Thompson) ---------------------------------------------------------------------- Background: Refactoring is the process of changing the structure of programs without changing their functionality, i.e., refactorings are meaning-preserving program transformations that implement design changes. For more details about refactoring, about our project and for background on HaRe, see our project pages and the papers/presentations/catalogue/demo/etc. available there, especially our contribution to this year's Haskell Workshop. HaRe - the Haskell Refactorer: HaRe is our prototype tool supporting a first few basic refactorings for Haskell 98 (see README.txt for known issues and limitations). It is implemented as a separate refactoring engine (on top of Programatica's Haskell frontend and Strafunski's generic traversal strategy library), with small scripting frontends that call this engine from either Vim or Emacs. The refactoring engine itself has been seen to build (with ghc-5.04.3) and run on most flavours of Windows (cygwin needed to build) and on Suns (binutils recommended to build), so we expect it to build and work on other unix-like platforms with almost no changes. In other words, we've tried to make sure that most of you should be able to build and use HaRe from your favourite OS/editor. Currently supported refactorings: removeDef : remove an unused definition duplicateDef : duplicate a definition under a new name liftToTopLevel : move a local definition to top level liftOneLevel : move a local definition one level up demote : move a definition local to point of use rename : rename an identifier introNewDef : turn expression into use of new definition unfoldDef : replace use of identifier by right-hand side addOneParameter: add parameter to definition rmOneParameter : remove unused parameter from definition generaliseDef : turn expression on rhs of definition into new parameter of that definition A series of screenshots illustrating some of the tasks one might want to accomplish with these refactorings can be found via the HaRe page (see above for URL). Caveats (see also README.txt): Please keep in mind that this is a prototype, so we do not recommend to use it on your productions sources just yet. Just play with it to get an idea of tool-supported refactoring in Haskell, and send us your feedback and bug-reports. Our goal is to develop this into a tool that many of you will find indispensible for Haskell development, and while we won't be able to follow every suggestion, we've got almost two more years in which to work towards this goal!-) History: Functionally, this is still roughly the snapshot you've seen at the Haskell workshop, packaged up for relative ease of build/use. Indeed, interim snapshots have been available all through September, and some of you have already played with those. The earliest snapshots were somewhat buggy, but over the last weeks the software has stabilised to the extent that we are back to Bug 0 (aka: insufficient test-coverage!-), and the time has come to distribute the current snapshot more widely.

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