October 2005 - Haskell

ANNOUNCE: pam-1.0
by Henning Günther 06 Oct '05

06 Oct '05

pam-0.1 ------- Haskell bindings for pam. Weeeeeee! This is my first release _ever_. I've created it mainly for learning reasons and just want to share it with the haskell community. See http://haskell.org/pam for more information about it. Feedback is very welcome. :) It's very untested yet, so it'll possibly crash, turn your computer into smoke and talk dirty to you. Just don't blame me, I've only written it.

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RE: [Haskell] strictness of putChar: report incomplete?
by Simon Marlow 06 Oct '05

06 Oct '05

On 05 October 2005 17:05, Lennart Augustsson wrote: > Wolfgang Jeltsch wrote: >> Am Mittwoch, 5. Oktober 2005 16:22 schrieb Simon Marlow: >> >>> [...] >> >> >>> Also, GHC's optimiser currently treats (_|_ :: IO a) and (do _|_; >>> return ()) as interchangeable, which is naughty, and people have >>> occasionally noticed, but the benefits can sometimes be huge. It >>> is this distinction that makes it hard to optimise IO code in a >>> Haskell compiler, though. >> >> >> I think, seq should be a method of a type class. Then we could >> forbid applying seq to a function, we could forbid applying seq to >> an IO expression and we could forbid applying seq to expressions of >> any type with hidden implementation for which we don't want to >> provide bottom tests. > > I agree with you. And that is how it used to be, but then > some people didn't think that was convenient enough so now > we are stuck with a seq that (IMHO) stinks. :) Having a seq that works on anything is occasionally very useful for fixing space leaks, and the type class version was kind of ugly and unwieldy. The type class pops up when you use ! in a data declaration, which looks strange. But I agree that polymorphic seq does have some painful side effects. Cheers, Simon

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RE: [Haskell] Making shared libraries with Haskell
by Simon Marlow 06 Oct '05

06 Oct '05

On 26 September 2005 08:57, Joel Reymont wrote: > Is the procedure of creating shared libraries with Haskell and > loading them from C described somewhere? > > Is this even possible? It currently isn't possible to build a Unix-style .so from Haskell code using GHC, although there is work in this direction (PIC and shared libraries are supported on MacOS X, and other platforms are in progress). It is possible to build a Windows DLL from Haskell code, although currently all the Haskell code has to reside in a single DLL. Again, this is a restriction we intend to lift in the future. It has been working before, but bitrotted due to fragility and lack of developer resources. Cheers, Simon

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Newbie quick questions
by Mike Crowe 05 Oct '05

05 Oct '05

Hi folks, I ran across Haskell at the Great Win32 Computer Language Shootout. A friend approached me with a potential large application to develop. The idea of a language which can reduce time to design and make better code is very intriguing. I was looking at prototyping in Python using wxWindows as the GUI. I see Haskell has wxWindows libraries as well. So, here's some newbie questions I couldn't get from 2-3h on the various web sites: 1) Can I develop a Windows application to sell? Or is Haskell not really geared for that? 2) Say a team wants to develop a larger application, like a CRM system. In "thinking" in functional programming, can a team split up work and implementation and work together? In other words, how easily does Haskell adapt to a team approach? 3) Again, using a CRM tool as an example, what is the advantage to developing an application like this in Haskell vs. any other language? If I really invest the time, can I get this done quicker in Haskell? Sell me on this, please. 3) I'm a very top-down programmer. I like to start at the "big-picture" and work my way down in implementation. Does this adapt to Haskell, or am I missing the point? TIA! Mike

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RE: [Haskell] strictness of putChar: report incomplete?
by Simon Marlow 05 Oct '05

05 Oct '05

On 04 October 2005 14:16, Duncan Coutts wrote: > On Tue, 2005-10-04 at 13:46 +0100, Malcolm Wallace wrote: >> I wrote: >> >>>> ghc: >>>> putChar _|_ -> _|_ >>>> >>>> hugs: >>>> putChar _|_ -> valid IO () >>> >>> I think it comes down to buffering behaviour doesn't it? >> >> Having reviewed the IRC logs, I see I was talking nonsense. >> >> You want to be able to store a closure for (putChar undefined) in a >> data structure, which seems like a perfectly reasonable thing to do. >> Provided the IO action is never actually run (after being retrieved >> from the data structure), the program really ought not to crash. >> >> I see that nhc98 and hbc agree with Hugs on this behaviour, so ghc >> _must_ be wrong. :-) > > Looking at GHC's library code we see that it is indeed forcing the > char early: > > hPutChar :: Handle -> Char -> IO () > hPutChar handle c = > c `seq` do > ... Fixed. However, I have a hunch that there are a *lot* of library functions whose strictness isn't completely specified by the report. Basically anything for which the report doesn't give the full code, except of course primitives which usually must be strict. This is only a hunch - I haven't actually gone looking for any. I suspect we get away with it most of the time because the desired strictness is "obvious" and/or the compilers all agree. Arguably, nothing returning IO should ever be strict, but you only have to use pattern matching in the implementation to violate that rule. Also, GHC's optimiser currently treats (_|_ :: IO a) and (do _|_; return ()) as interchangeable, which is naughty, and people have occasionally noticed, but the benefits can sometimes be huge. It is this distinction that makes it hard to optimise IO code in a Haskell compiler, though. Cheers, Simon

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RE: [Haskell] strictness of putChar: report incomplete?
by Simon Marlow 05 Oct '05

05 Oct '05

On 05 October 2005 15:46, Ross Paterson wrote: > On Wed, Oct 05, 2005 at 03:22:29PM +0100, Simon Marlow wrote: >> Also, GHC's optimiser currently treats (_|_ :: IO a) and (do _|_; >> return ()) as interchangeable, which is naughty, and people have >> occasionally noticed, but the benefits can sometimes be huge. > > What's wrong with identifying them? You're not expecting the monad > laws to hold, are you? No, of course I don't expect the monad laws to hold :) But the intended meaning of (do _|_; return () :: IO ()) `seq` True is True, not _|_, right? This isn't made explicit in the report, but it's how we all understand the IO monad to work, and perhaps derives from the well-known implementation of (IO a) as (World -> (a,World)). Cheers, Simon

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ANNOUNCE: cpphs-1.0
by Malcolm Wallace 05 Oct '05

05 Oct '05

cpphs-1.0 --------- Announcing a new release of cpphs, a Haskell re-implementation of the C pre-processor. This release mainly has very minor bugfixes, indicating (I hope) that cpphs has reached a state of reasonable stability and maturity. http:/haskell.org/cpphs Recent Changes: * Add a compatibility script cpphs.compat, allowing cpphs to act as a drop-in replacement for cpp, e.g. ghc -cpp -pgmP cpphs.compat * Place quotes around replacements for special macros __FILE__, __DATE__, and __TIME__. * If no files are specified, read from stdin. * Ignore #! lines (e.g. in scripts) * Parse -D commandline options once only, and consistently with cpp, i.e. -Dfoo means foo=1 * Fix compatibility with preprocessors like hsc2hs, which use non-cpp directives like #def. They are now passed through to the output with a warning to stderr.

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Natural Language and Knowledge Representation/Reasoning (CFP)
by Jana Sukkarieh 04 Oct '05

04 Oct '05

[Apologies for x-postings] NATURAL LANGUAGE AND KNOWLEDGE REPRESENTATION (NL-KR) Special Track at FLAIRS 2006 SECOND CALL FOR PAPERS Holiday Inn Melbourne Oceanfront, Melbourne Beach, FLORIDA, USA MAIN CONFERENCE: 11-12-13 MAY 2006 Special track web page: http://users.ox.ac.uk/~lady0641/Flairs06_NL_KR Main conference web page: http://www.indiana.edu/~flairs06 PURPOSE OF THE NL-KR TRACK We believe the Natural Language Processing (NLP) and the Knowledge Representation (KR) communities have common goals. They are both concerned with representing knowledge and with reasoning, since the best test for the semantic capability of an NLP system is performing reasoning tasks. Having these two essential common grounds, the two communities ought to have been collaborating, to provide a well-suited representation language that covers these grounds. However, the two communities also have difficult-to-meet concerns. Mainly, the semantic representation (SR) should be expressive enough and should take the information in context into account, while the KR should be equipped with a fast reasoning process. The main objection against an SR or a KR is that they need experts to be understood. Non-experts communicate (usually) via a natural language (NL), and more or less they understand each other while performing a lot of reasoning. An essential practical value of representations is their attempt to be transparent. This will particularly be useful when/if the system provides a justification for a user or a knowledge engineer on its line of reasoning using the underlying KR (i.e. without generating back to NL). We all seem to believe that, compared to Natural Language, the existing Knowledge Representation and reasoning systems are poor. Nevertheless, for a long time, the KR community dismissed the idea that NL can be a KR. That's because NL can be very ambiguous and there are syntactic and semantic processing complexities associated with it. However, researchers in both communities have started looking at this issue again. Possibly, it has to do with the NLP community making some progress in terms of processing and handling ambiguity, the KR community realising that a lot of knowledge is already 'coded' in NL and that one should reconsider the way they handle expressivity and ambiguity. This track is an attempt to provide a forum for discussion on this front and to bridge a gap between NLP and KR. A KR in this track has a well-defined syntax, semantics and a proof theory. It should be clear what authors mean by NL-like, based on NL or benefiting from NL (if they are using one). It does not have to be a novel representation. NL-KR TRACK TOPICS For this track, we will invite submissions including, but not limited to: a. A novel NL-like KR or building on an existing one b. Reasoning systems that benefit from properties of NL to reason with NL c. Semantic representation used as a KR : compromise between expressivity and efficiency? d. More Expressive KR for NL understanding (Any compromise?) e. Any work exploring how existing representations fall short of addressing some problems involved in modelling, manipulating or reasoning (whether reasoning as used to get an interpretation for a certain utterance, exchange of utterances or what utterances follow from other utterances) with NL documents f. Representations that show how classical logics are not as efficient, transparent, expressive or where a one-step application of an inference rule require more (complex) steps in a classical environment and vice-versa; i.e. how classical logics are more powerful, etc g. Building a reasoning test collection for natural language understanding systems: any kind of reasoning (deductive, abductive, etc); for a deductive test suite see for e.g. deliverable 16 of the FraCas project (http://www.cogsci.ed.ac.uk/~fracas/) Also, look at textual entailment challenges 1 and 2 <http://www.pascal-network.org/Challenges/RTE> h. Comparative results (on a common test suite or a common task) of different representations or systems that reason with NL (again any kind of reasoning). The comparison could be either for efficiency, transparency or expressivity i. Knowledge acquisition systems or techniques that benefit from properties of NL to acquire knowledge already 'coded' in NL j. Automated Reasoning, Theorem Proving and KR communities views on all this NL_KR TRACK PROGRAM COMMITTEE James ALLEN, University of Rochester, USA Patrick BLACKBURN, Institut National de Recherche en Informatique, France Johan BOS, University of Edinburgh, UK Richard CROUCH, Palo Alto Research Centre, USA Maarten DE RIJKE, University of Amsterdam, The Netherlands Anette FRANK, DFKI, Germany Fernando GOMEZ, University of Central Florida, USA Sanda HARABAGIU, University of Texas at Dallas, USA John HARRISON, Intel, USA Jerry HOBBS, Information Sciences Institute, USA Chung Hee HWANG, Raytheon Co., USA Michael KOHLHASE, International University Bremen, Germany Shalom LAPPIN, King's College, UK Carsten LUTZ, Dresden University of Technology, Germany Dan MOLDOVAN, University of Texas at Dallas, USA Jeff PELLETIER, Simon Fraser University, Canada Stephen PULMAN, University of Oxford, UK Lenhart SCHUBERT, University of Rochester, USA John SOWA, VivoMind Intelligence, Inc., USA Jana SUKKARIEH, University of Oxford, UK (Chair) Geoff SUTCLIFFE, Miami University, USA Timothy WILLIAMSON, University of Oxford, UK NL_KR TRACK INVITED SPEAKER John SOWA, VivoMind Intelligence, Inc., US FLAIRS 2006 INVITED SPEAKERS Alan BUNDY, University of Edinburg, Scotland Bob MORRIS, Nasa Ames Research Center, USA Mehran SAHAMI, Standford University and Google, USA Barry SMYTH, University College Dublin, Ireland NL-KR TRACK PROPOSED BY Jana Sukkarieh, University of Oxford, UK email: J.Sukkarieh.94(a)cantab.net WEB and TECH SUPPORT Simon Dobnik, University of Oxford, UK email: Simon.Dobnik(a)clg.ox.ac.uk SUBMISSION DETAILS Submissions must arrive no later than 21 November 2005. Only electronic submissions will be considered. Details about submission can be found on : http://users.ox.ac.uk/~lady0641/Flairs06_NL_KR/submission_details.html Selected papers will be considered for publication in a special journal issue of "The journal of Logic and Computation" in the 2nd half of 2006. PROCEEDINGS Printed Proceedings will be published only on demand. Proceedings on CD will be provided to all. IMPORTANT DATES * Submission of papers: 21 November, 2005 * Notification of acceptance: 20 January, 2006 * Final version of the paper is due : 13 February, 2006 * Main Conference: 11-13 May 2006 * Track: max 1 day during the main conference Those interested in running a demo please contact Jana Sukkarieh <J.Sukkarieh.94(a)cantab.net> or Simon Dobnik <Simon.Dobnik(a)clg.ox.ac.uk>.

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Haskell Weekly News: October 4, 2005
by John Goerzen 04 Oct '05

04 Oct '05

Haskell Weekly News: October 4, 2005 Greetings, and thanks for reading the 10th issue of HWN, a weekly newsletter for the Haskell community. Each Tuesday, new editions will be posted (as text) to [1]the Haskell mailing list and (as HTML) to [2]The Haskell Sequence. 1. http://www.haskell.org/mailman/listinfo/haskell 2. http://sequence.complete.org/ New Releases The Monad.Reader, Issue 5. Shae Matijs Erisson [3]announced the release of the fifth issue of The Monad.Reader, the online magazine devoted to Haskell. Subjects in this issue include a short introduction to Haskell, generating polyominoes, a ray tracer, number parameterized types, practical graph manipulation, and a short introduction to software testing in Haskell. TMR is available [4]online. 3. http://article.gmane.org/gmane.comp.lang.haskell.general/12216 4. http://www.haskell.org/tmrwiki/IssueFive Discussion Quiet or Busy? It's been a quiet week on the Haskell lists, so this week's HWN is a bit sparse. But that's because many Haskellers were at the Haskell workshops at ICFP in Estonia. I expect we'll see some fallout from those workshops on the list in the coming week. Haskell workshop items. Over on the IRC channel [5]logs from September 30, there was a live conversation beginning at 15:36:33 of the "Future of Haskell discussion." Autrijus Tang's journal had several pages of entries, including one [6]providing a nice summary. 5. http://meme.b9.com/cview.html?channel=haskell&date=050930 6. http://use.perl.org/~autrijus/journal/26953 Endian conversion. Joel Reymont asked about converting binary data in a network protocol, and several suggestions were posted in the resulting [7]discussion. 7. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/8556 Is putChar strict? John Meacham [8]asked this question, and pointed out that different Haskell compilers/interpreters are behaving in different ways. 8. http://thread.gmane.org/gmane.comp.lang.haskell.general/12224 About Haskell Weekly News Want to continue reading HWN? Please help us create new editions of this newsletter. Please see the [9]contributing information, or send stories to hwn -at- complete -dot- org. There is also a Darcs repository available. 9. http://sequence.complete.org/hwn-contrib

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strictness of putChar: report incomplete?
by John Meacham 04 Oct '05

04 Oct '05

The report does not seem to specify whether putChar _|_ is _|_ or not. (although it might be implied somewhere I didn't see) I orginally noticed this when jhc treated it as so and I considered this a bug since the argument should not be evaluated until the action is actually executed. however, it appears ghc has the same bug, or my reasoning is wrong. not only that, but hugs and ghc disagree with each other. ghc: putChar _|_ -> _|_ putStr _|_ -> valid IO () hugs: putChar _|_ -> valid IO () putStr _|_ -> valid IO () all the IO actions are bottom on execution of course. I believe the hugs behavior is correct and ghc and jhc are wrong, but there were differing opinions on #haskell. John -- John Meacham - ⑆repetae.net⑆john⑈

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