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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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Announce: Update of the Haskell Bibliography
by Benderjgdefault＠aol.com 28 Nov '02

28 Nov '02

I have just finished a major update of the Haskell bibliography: http://haskell.readscheme.org/ This update includes 135 new citations (a 40% increase in the size of the bibliography). Jim Bender

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RE: "cartesian classes"
by David Bergman 27 Nov '02

27 Nov '02

Frank, Then we do mean the same thing, because a relation is indeed a subset of a cartesian product ;-) That is what I meant with "cartesian classes". Sorry for any confusion that might have caused. And, I am fully aware that most people in this mail group are quite familiar with simple set-theoretic concepts, but since the question was raised, and I know that there are a few more pragmatic programmers aboard, I assumed it would not hurt to explain that a bit. I still think "multi-parameter classes" is bad terminology, though, since the subconstruct "C a b" in the class declaration "class C a b where ..." does not denote a class (template), but the "C" does... This is in contrast to "multi-parameter types", such as "data Tree a b = Leaf a | Branch b (Tree a b) (Tree a b)" where the subconstruct "Tree a b" does denote a type (template). Maybe I am the only one with this view... Thanks for the concrete usage info for functional dependencies restricting these "class relations". David -----Original Message----- From: Frank Atanassow [mailto:franka@cs.uu.nl] Sent: Wednesday, November 27, 2002 10:15 AM To: David Bergman Subject: Re: "cartesian classes" David Bergman wrote (on 26-11-02 13:18 -0500): > > What do you mean by "cartesian classes"? Do you mean multi-parameter > > type classes? > > > They're supported by GHC and Hugs, but not NHC98 or HBC. The same goes > > for functional dependencies. > > Yes, I meant what is commonly known as multi-parameter type classes, > although that name IMHO does not make much sense, since only the > explicitly parameterized type class should qualify as a any-parameter > type class, with the (non-Haskell syntax) "b in C a", where "a" is the > parameter, "C a" the resulting type class, and, finally, "b" the (type) > element of the class. > > In a regular class declaration, "C a", I would argue that "C" is the > class, not being single-parameter, but zero-parameter. It is sometimes > unfortunate that the syntax of Haskell makes this look like a > constructor... I'm afraid I don't understand this. If it helps, the way I think of classes is that they are predicates/relations at the type level; a multi-parameter class gives an n-ary predicate for n>1. So, in: class C a b c where ... C is a ternary predicate and instance C Int Char Int where ... says that (Int, Char, Int) is a member of C regarded as a subset of a product of sets. > What I meant by cartesian is that using several variables, you would get > (also in non-Haskell syntax) "(a, b, c) in C", i.e., the class actually > being a subclass of the third cartesian power of the universal > (implicit) type class. Yes, I know what cartesian products, categories and coordinate systems are, but I've never heard multi-parameter type classes referred to that way before. > If both GHC and Hugs support functional dependencies, I would probably > dare to wander off into the mysterious land of Haskell 2. > > A very concrete, but naïve, question: what is the syntax for defining > functional dependencies in Hugs and GHC? Since Mark Jones' syntax was > abstract in his paper, it is kind of hard to deduce an ASCII equivalence > (I have tried to figure out how to create a curly arrow from the > keyboard ;-) The syntax is, for example: class Class a b c d | a c -> b d where ... meaning that a and c determine b and d, so if the declaration instance Class A B C D is in scope, then, for all B', D' s.t. B'/=B or D'/=D, it is illegal for there to be a declaration of the form instance Class A B' C D' also in scope. There is an account of the syntax and semantics in the Hugs manual, 7.1.1.3: http://cvs.haskell.org/Hugs/pages/hugsman/exts.html -- Frank

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IEEE/ACM MEMOCODE'03: Call for papers
by Miroslav Velev 27 Nov '02

27 Nov '02

Call for Papers: IEEE/ACM METHODS and MODELS for CODESIGN (MEMOCODE 2003) Homepage: http://www.irisa.fr/manifestations/2003/MEMOCODE/ Sponsors: IEEE Circuits and System Society ACM Special Interest Group on Digital Automation IEEE Computer Society, Digital Automation Technical Committee Organized at the Relais du Mont Saint-Michel in cooperation with INRIA and IRISA. High-level design and modeling of hardware and embedded hardware-software systems has gained prominence in the face of rising technological complexities and performances, as well as shortened time to market demands for complex electronic equipments. Numerous programming languages, tools and frameworks have been proposed in the past to design, simulate and validate heterogeneous systems within an abstract and rigorously defined mathematical model. Recently, attention has shifted to modeling frameworks based on variants of general purpose programming languages, in response to the growing industry demand for use of higher levels of abstraction in the system design process. Meanwhile, the installed base of existing IP adds further requirements for the adaptation of existing IPs with new services within complex integrated architectures, calling for appropriate methodological approaches. Whereas abstract frameworks are ways to unambiguously model the essence of hardware software systems, help understand the design, implement formal correctness proofs, predict performances and other metrics; general-purpose languages facilitate programming, reuse and gain from the popularity of C, C++ like languages. Still, important gaps need to be filled and bridges to be built between the theory of modeling and the practice of programming. Languages shall benefit the rigorousness of models and models the experience of programming practice. This calls for finding a convergence between both approaches. A focus on formal methods (programming and concurrency models, analysis and verification techniques) for hardware/software codesign is necessary, because language in which system designers work are general-purpose ones, because the only way provably correct systems can be constructed are by technology transfer of research in formal methods. Opening speaker Jose Meseguer (SRI) Invited speakers Ahmed Jerraya (IMAG) Nancy Lynch (MIT) Ken McMillan (Cadence) Program co-chairs Sandeep K. Shukla (Virginia Tech) Jean-Pierre Talpin (INRIA) Program committee Gul Agha (University of Illinois at Urbana-Champaign) Arvind (Massachussets Institute of Technology) Brian Bailey (Mentor Graphics) François Bodin (University of Rennes-IRISA) Forrest Brewer (University of California at Santa Barbara) Stephen Edwards (Columbia University) Hans Eveking (University of Darmstadt) Harry Foster (Verplex Systems) Franco Fummi (University of Verona) Vijay Kumar Garg (University of Texas at Austin) Rajesh Gupta (University of California at San Diego) Connie Heitmeyer (Naval Research Laboratory) James Hoe (Carnegie Mellon University) Alan Hu (University of British Columbia) Marta Kwiatkowska (University of Birmingham) Kim Larsen (Aalborg University) Paul Le Guernic (INRIA-IRISA) Stan Liao (Synopsys) Grant Martin (Cadence) Hillel Miller (Motorola) Zebo Peng (Linköping University) Carl Pixley (Synopsys) Rob Slater (Motorola) Sandeep Kumar Shukla (Virginia Tech) Jean-Pierre Talpin (INRIA-IRISA) Marten Van Hulst (Philips Research) Miroslav Velev (Georgia Tech) Wayne Wolf (Princeton University) Steering committee Masahiro Fujita (University of Tokyo) Vijay Kumar Garg (University of Texas at Austin) Paul Le Guernic (INRIA-IRISA) Rajesh Gupta (University of California at Irvine) Nancy Lynch (Massachussets Institute of Technology)

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Linking ghc .o files with MSVC++
by Mauricio Carvalho 26 Nov '02

26 Nov '02

Hi I need help specifically building Haskell functions that I can call from C++ (or C). I looked at the Foreign Function Interface explanation at GHC user's guide, but I didn't understand itt well, and I'm not succeeding at doing it. I'm using GCH 5.04.1 in Win32 environment, and Microsoft Visual C++ That is as far as I got: I compiled a simple MyModule.hs file with ghc -c -fffi MyModule.hs It was just a test module that conatined a factorial function called fac. Here is the source: module MyModule where foreign export ccall "fac" fac :: Int -> Int fac :: Int -> Int fac n | n <= 0 = 1 | otherwise = n * fac(n-1) It gave me 4 files: MyModule_stub.h, MyModule_stub.c, MyModule_stub.o, MyModule.o (and a MyModule.hi, but I think not relevant for linking with C) I was thinking that a .o and a .h file would be sufficient for the linking; anyway, I copied those 4 files to my c++ program directory, included the .h file at my c++ main program, add the file MyModule_stub.o to the linking process and tried to compile. That is my c++ program: #include <iostream> #include "MyModule_stub.h" int main(){ std::cout << fac(10) << std::endl; return 0; } The linker complains that some function calls are unresolved: Compiling... principal.cpp Linking... MyModule_stub.o : error LNK2001: unresolved external symbol _MyModule_zdffac_closure MyModule_stub.o : error LNK2001: unresolved external symbol _GHCziTopHandler_runNonIO_closure MyModule_stub.o : error LNK2001: unresolved external symbol _rts_getInt MyModule_stub.o : error LNK2001: unresolved external symbol _rts_checkSchedStatus MyModule_stub.o : error LNK2001: unresolved external symbol _rts_mkInt MyModule_stub.o : error LNK2001: unresolved external symbol _rts_apply MyModule_stub.o : error LNK2001: unresolved external symbol _rts_evalIO Debug/templates.exe : fatal error LNK1120: 7 unresolved externals Error executing link.exe. I tried to use the file MyModule.o, instead of MyModule_stub.o, and got mor unresolved symbols. What was worse, the function symbol itself was unresolved: Linking... MyModule.o : error LNK2001: unresolved external symbol _getStablePtr MyModule.o : error LNK2001: unresolved external symbol _GHCziNum_Szh_con_info MyModule.o : error LNK2001: unresolved external symbol _stg_upd_frame_info MyModule.o : error LNK2001: unresolved external symbol _GHCziBase_ZMZN_closure MyModule.o : error LNK2001: unresolved external symbol _stg_ap_2_upd_info MyModule.o : error LNK2001: unresolved external symbol _GHCziBase_ZC_con_info MyModule.o : error LNK2001: unresolved external symbol _stg_sel_0_upd_info MyModule.o : error LNK2001: unresolved external symbol _GHCziBase_Izh_static_info MyModule.o : error LNK2001: unresolved external symbol _GHCziReal_zdfIntegralInt_closure MyModule.o : error LNK2001: unresolved external symbol _stg_CAF_BLACKHOLE_info MyModule.o : error LNK2001: unresolved external symbol _newCAF MyModule.o : error LNK2001: unresolved external symbol _stg_IND_STATIC_info MyModule.o : error LNK2001: unresolved external symbol _stg_INTLIKE_closure principal.obj : error LNK2001: unresolved external symbol _fac Debug/templates.exe : fatal error LNK1120: 14 unresolved externals Error executing link.exe. Even trying to include both .o modules to the linking process didn't help If I link this module to a Haskel program, it works out fine... So, it seems that when I create an object file from a Haskell module, I must link with other object files, that ghc probably links automatically. Is it true? An being the case, how can one know which object files to link? Please, understand that I'm quite a newbie using haskell when answering. Thanks for any help, Mauricio

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Best recursion choice for "penultimax"
by Dr Mark H Phillips 26 Nov '02

26 Nov '02

Hi, I have just implemented the function "penultimax" which takes a list of positive integers and produces the "penultimate maximum", that is, the next biggest integer in the list after the maximum. Eg: penultimax [15,7,3,11,5] = 11 One implementation is: penultimax :: [Int] -> Int penultimax ms = foldr max 0 (filter (<msMax) ms) where msMax = foldr max 0 ms But I can think of two variations which might be more efficient: penultimax2 :: [Int] -> Int penultimax2 ms = penultimax2' ms 0 0 where penultimax2' :: [Int] -> Int -> Int -> Int penultimax2' [] p q = q penultimax2' (m:ms) p q | m>p = penultimax2' ms m p | m>q = penultimax2' ms p m | otherwise = penultimax2' ms p q penultimax3 :: [Int] -> Int penultimax3 ms = snd (maxpenmax ms) where maxpenmax :: [Int] -> (Int,Int) maxpenmax [] = (0,0) maxpenmax [m] = (m,0) maxpenmax (m:ms) | m>p = (m,p) | m>q = (p,m) | otherwise = (p,q) where (p,q) = maxpenmax ms How do I work out which is best to use? Is there one clear "winner", or will they each have pros and cons? Thanks, Mark. -- Dr Mark H Phillips Research Analyst (Mathematician) AUSTRICS - smarter scheduling solutions - www.austrics.com Level 2, 50 Pirie Street, Adelaide SA 5000, Australia Phone +61 8 8226 9850 Fax +61 8 8231 4821 Email mark(a)austrics.com.au

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