November 2002 - Haskell

Research Grants at UPM
by clip-small＠clip.dia.fi.upm.es 29 Nov '02

29 Nov '02

[Apologies for multiple copies] [Please, post as you deemed appropriate] The CLIP Group, Technical University of Madrid (UPM), offers 2 pre-doctoral, 4-year scholarships (research assistant level) available within the area of programming language technology: program analysis, transformation, and compilation. The work, intended to lead to a Ph.D., is to be done as a member of the CLIP Group http://www.clip.dia.fi.upm.es, within a nationally funded research project. The scholarships are funded by the Ministry of Science and Technology http://www.mcyt.es. Requirements for candidates are detailed in the CLIP group's job openings page: http://www.clip.dia.fi.upm.es/Job_Openings/jobs.html Application deadline is December 6th, 2002 (strict). Please, send a short CV, including previous research work and publications, and 1 to 3 references in electronic form in reply to this message. The main theme of the work envisioned within the scholarships is to advance the state of the art of automatic program manipulation techniques. The objective is to increase the power of such techniques and integrate them in practical tools within the Ciao multi-paradigm programming system, including logic, functional, constraint, and object-oriented programming. One additional objective is to target program optimizations to the needs of the computational elements of pervasive computing environments. One of the main lines of work implies extending the program compilation and development tools so that they can be used in such an environment to reduce program resource consumption and to instrument programs to perform dynamic control of such consumption during execution. The final aim is to develop an environment that would be an ideal candidate for programming ambient intelligence in mobile and pervasive computing environments.

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nub
by Christian Maeder 29 Nov '02

29 Nov '02

> > What does "nub" stand for? (This is the first I've heard of it.) > Hmm, maybe that's not such a great explanation. I wonder who can come up > with the best acronym? My contribution is > > "Note Unique Bits" "no duplicates" (or "no doubles") although that's no acronym Christian

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question about haskell report terminology
by Bernard James POPE 29 Nov '02

29 Nov '02

Hi All, In section 4.4.3 "Function and Pattern Bindings" of the Haskell 98 Report, it gives the following translation: ---- (The general binding form of a function is): x p_11 ... p_1k match_1 ... x p_n1 ... p_nk match_n Translation: The general binding form for functions is semantically equivalent to the equation (ie simple pattern binding): x = \x_1 ... x_k -> case (x_1, ..., x_k) of (p_11, ..., p_1k) match_1 ... (p_n1, ..., p_nk) match_n where x_i are new identifiers ---- What does it mean by "semantically equivalent". A rough approximation is "has the same meaning", but that depends on how you define the "meaning". For example: foo x = show x versus foo = \x -> show x I think the answer to the question is something like: this rule is intended to translate Haskell into the kernel, but it is not an equivalence that the programmer may (always) use in their own program (ie it is applicable only after type checking). I'm not sure where this rule fits into the definition of the language. Cheers, Bernie.

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RE: Implementing forward refs in monadic assembler and interprete r
by Erkok, Levent 29 Nov '02

29 Nov '02

Hi, As Ross pointed out, forward labels can easily be implemented using recursive monadic bindings. There're a number of alternatives as to which underlying monad you want to use. Continuations are problematic, but this problem can be solved by using a simple state monad: please see the attached file for one possible implementation. The variables test1-test4 (see the end of the file) are bound to the compiled and interpreted versions of your examples compute112 and compute12. Note: I had to add a "return ()" to the end of your compute12 example, since mdo-notation requires the last generator to be an expression, just like an ordinary do-expression. You need a fairly recent version of Hugs to run this example, November 2002 release would do (try with -98). For ghc, you need the CVS version, or wait till the next release. As far as I know, no other implementation supports mdo, nor there are any plans for it. -Levent. > -----Original Message----- > From: Mike Gunter [mailto:m@ryangunter.com] > Sent: Friday, November 15, 2002 1:38 AM > To: haskell(a)haskell.org > Subject: Implementing forward refs in monadic assembler and interpreter > > > I need to implement an assembler and interpreter for a simple > instruction set. For example, this code > > \begin{code} > compute112 = do > { zero r1 > ; zero r2 > ; addi r2 3 -- loop three times > ;topLoop <- label > ; addi r1 4 > ; addi r2 (-1) -- decrement loop counter > ; brPositive r2 topLoop > ; add r1 100 > } > \end{code} > > would result in register r1 having a value 112. Without forward > branches, the implementation is reasonably straightforward. The > assembler can use a Monad with state and writer capabilities. The > interpreter can use a continuation monad to implement branches and a > state monad for the machine state. > > However, forward branches make things harder. I'd like to be able to > write something along the lines of: > > \begin{code} > compute12 = mdo > { zero r1 > ; zero r2 > ; addi r2 3 -- loop three times > ;topLoop <- label > ; addi r1 4 > ; addi r2 (-1) -- decrement loop counter > ; brPositive r2 topLoop > ; mov r3 r1 > ; addi r3 (-10) > -- !!! Forward branch: > ; brPositive r3 out -- if r1 > 10 don't add 100 > ; add r1 100 > ;out <- label > } > \end{code} > > but it's not clear to me how to implement it. I'd be willing to > accept a somewhat less clean version (for instance, with more > cumbersome forward references.) > > Any help would be greatly appreciated. > > thanks, > mike > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell

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You can finally run your Chameleon programs!
by Martin Sulzmann 28 Nov '02

28 Nov '02

The latest Chamleon release includes a compiler. Chameleon programs are translated into plain Haskell (= Hindley/Milner subset plus polymorphic recursion). Note that Chameleon comes also with a type debugger. Check out http://www.comp.nus.edu.sg/~sulzmann/chameleon/ for the latest release including a number of examples. Martin

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Running out of memory in a simple monad
by Magnus Lindberg 28 Nov '02

28 Nov '02

{- Hi! I have problems with monads and memory. I have a monad through which I thread output. If I do the concatenation of the output-strings in one way Hugs runs out of memory, but if I do it in another way everything works. I can't see why the first way doesn't work but the second is OK. I woudl appreciate if someone could tell me what I am doing wrong. Here is the non-working monad: -} data M a = M (String -> (a, String)) instance Monad M where return x = M $ \o -> (x, o) M io >>= fio = M $ \o0 -> let (r1, o1) = o0 `seq` io o0 M io2 = r1 `seq` fio r1 in io2 o1 putCharM c = M $ \o -> ((), o ++ [c]) -- Is this stupid in some way? runM :: M a -> IO() runM (M io) = let (r, outp) = io "" in putStr outp crashHugs 0 = return () crashHugs n = do putCharM 'x'; crashHugs (n-1) r = runM (crashHugs 50000) {- Besides, the output generated when one runs `r' (with a smaller number, for example r = 4000) above is in the beginning written in a very slow pace but then the delay between each char decreases and finally everything is written very fast (but not for the working monad below) Well, here is the working monad: -} {- data M a = M (a, String) instance Monad M where return x = M (x, "") M f >>= k = M $ let (x, o) = f M f2 = k x (x', o') = f2 in (x', o ++ o') putCharM c = M ((), [c]) runM :: M a -> IO() runM (M f) = let (r, outp) = f in putStr outp thisIsOk 0 = return () thisIsOk n = do putCharM 'x'; thisIsOk (n-1) r = runM (thisIsOk 50000) -} {- So, it works when I concatenate the output in `>>=' but not (as in the first monad) in putChar... I can't see why :( Keen regards, Magnus Lidnberg -}

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EACL2003: 2nd Call for Workshop Papers
by steven.krauwer＠elsnet.org 28 Nov '02

28 Nov '02

EACL 2003 in Budapest, April 12-17, 2003 Workshop Programme and Second Call for Workshop Papers Important dates for all workshops: ---------------------------------- Submission deadline: Jan 07, 2003 Notification: Jan 28, 2003 Deadline for final papers: Feb 13, 2003 Workshop dates: Apr 13/14, 2003 Conference dates: Apr 12-17, 2003 Important URLs: --------------- Main conference: http://www.conferences.hu/EACL03/ Workshops: http://www.elsnet.org/workshops Workshop overview: ------------------ Workshop w01: "MT and other language technology tools; Improving MT through other language technology tools; Resources and tools for building MT" URL: not available Organizer(s): Bente Maegaard Email: bente(a)cst.dk CfP: http://www.elsnet.org/workshops/w01.doc Date: April 13, 2003 ___________________________________________________________________ Workshop w02: "9th European Workshop on Natural Language Generation" URL: http://www.ags.uni-sb.de/~horacek/EACL-EWNLG03.html Organizer(s): Ehud Reiter Email: ereiter(a)csd.abdn.ac.uk CfP: http://www.elsnet.org/workshops/w02.txt Date: April 13+14, 2003 ___________________________________________________________________ Workshop w03: "4th International Workshop on Linguistically Interpreted Corpora (LINC-03)" URL: http://www.coli.uni-sb.de/linc03 Organizer(s): Silvia Hansen Email: hansen(a)CoLi.Uni-SB.DE CfP: http://www.elsnet.org/workshops/w03.txt Date: April 14, 2003 ___________________________________________________________________ Workshop w04: "Language Modeling for Text Entry Methods" URL: http://www.uni-koblenz.de/~compling/eaclws2003/ Organizer(s): Michael Kuhn Email: kuehn(a)uni-koblenz.de CfP: http://www.elsnet.org/workshops/w04.txt Date: April 13, 2003 ___________________________________________________________________ Workshop w05: "The Computational Treatment of Anaphora" URL: http://www.clt.mq.edu.au/eacl03ana.html Organizer(s): Rob Dale Email: rdale(a)ics.mq.edu.au CfP: http://www.elsnet.org/workshops/w05.txt Date: April 14, 2003 ___________________________________________________________________ Workshop w06: "Dialogue Systems: interaction, adaptation and styles of management" URL: http://www.dcs.shef.ac.uk/~roberta/eacl-w06.html Organizer(s): Kristiina Jokinen and Roberta Catizone Email: kjokinen@uiah.fi,R.Catizone@dcs.shef.ac.uk CfP: http://www.elsnet.org/workshops/w06.txt Date: April 13+14, 2003 ___________________________________________________________________ Workshop w07: "Evaluation Initiatives in Natural Language Processing: are evaluation methods, metrics and resources reusable?" URL: http://www.dcs.shef.ac.uk/~katerina/EACL03-eval Organizer(s): Katerina Pastra Email: e.pastra(a)dcs.shef.ac.uk CfP: http://www.elsnet.org/workshops/w07.txt Date: April 13, 2003 ___________________________________________________________________ Workshop w08: "Computational Linguistics for South Asian Languages -- Expanding Synergies with Europe" URL: not available Organizer(s): Durgesh Rao and Pat Hall Email: durgesh@saathi.ncst.ernet.in,p.a.v.hall@open.ac.uk CfP: http://www.elsnet.org/workshops/w08.txt Date: April 14, 2003 ___________________________________________________________________ Workshop w09: "Workshop on Finite State Methods in Natural Language Processing" URL: http://www-igm.univ-mlv.fr/~laporte/fsw-cfp.htm Organizer(s): Eric Laporte and Ken Beesley Email: eric.laporte@univ-mlv.fr,Ken.Beesley@xrce.xerox.com CfP: http://www.elsnet.org/workshops/w09.txt Date: April 13+14, 2003 ___________________________________________________________________ Workshop w10: "Language Technology and the Semantic Web: 3rd Workshop on NLP and XML (NLPXML-2003)" URL: http://www.cs.vassar.edu/~ide/events/NLPXML3.html Organizer(s): Nancy Ide and Graham Wilcock Email: ide@cs.vassar.edu,graham.wilcock@helsinki.fi CfP: http://www.elsnet.org/workshops/w10.txt Date: April 14, 2003 ___________________________________________________________________ Workshop w11: "Natural Language Processing (NLP) for Question-Answering" URL: not available Organizer(s): Bonnie Webber and Maarten de Rijke Email: bonnie@inf.ed.ac.uk,mdr@science.uva.nl CfP: http://www.elsnet.org/workshops/w11.txt Date: April 13, 2003 ___________________________________________________________________ Workshop w12: "Morphological Processing of Slavic Languages" URL: http://nl.ijs.si/mpsl03/ Organizer(s): Tomaz Erjavec and Dusko Vitas Email: Tomaz.Erjavec@ijs.si,vitas@matf.bg.ac.yu CfP: http://www.elsnet.org/workshops/w12.txt Date: April 13, 2003 ___________________________________________________________________ Contact info: - for the workshops in general: steven.krauwer(a)elsnet.org - for individual workshops: workshop organizers - for the main conference: kindl(a)sztaki.hu _______________________________________________________________

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slide: useful function?
by Markus.Schnell＠infineon.com 28 Nov '02

28 Nov '02

I want to propose the following function slide, which is like map, but depends not on one value of a list, but on several consecutive ones. slide :: ([a] -> b) -> [a] -> [b] slide f [] = [] slide f xs = f xs : slide f (tail xs) For example, this is useful for a digital filter, like lowpass = firfilter [0.005178,0.005712,0.00589,0.005712,0.005178] firfilter :: [Coeff] -> DigitalFilter firfilter b = slide (firfilter' b) where firfilter' b = sum . zipWith (*) b What do you think? Or is there already a function slide, just with another name? Markus -- Markus Schnell, Infineon Technologies AG

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summary of haskell desugaring?
by Bernard James POPE 28 Nov '02

28 Nov '02

Hi all, The Haskell Language report details a number of rules for simplifying the full syntax (list comprehensions, do notation, patterns and so on). I find it a lot of work to wade through the report finding all these rules. What I want is a summary of all the rules in one place. Preferably with some examples. Does anyone have such a thing? If no such thing exists, then I will make one myself and then make it available, but I thought I'd check first. I'm contemplating writing some software to go with it, but that might be a bit ambitious, we'll see. Cheers, Bernie.

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ANNOUNCE: rsa-haskell 1.1.0
by David Sankel 28 Nov '02

28 Nov '02

rsa-haskell 1.1.0 ================= This is an announcement for a version 1.1.0 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. Changes: Added AddZeros and SubZeros programs to fix previous m>pq errors. Now rsa-haskell's test runs without known error. Huge speedup in the RSAcrypt program. Useage messages now show for all user errors. All programs now support the -h, -?, and --help options. For more information and download: http://www.electronconsulting.com/rsa-haskell/ Please email comments, bugs, etc. to camio(a)yahoo.com. David J. Sankel

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