- Haskell - Haskell.org

announce: tour of Haskell Prelude document (for teaching etc)
by Bernard James POPE 11 Feb '02

11 Feb '02

Hi all, A while back I wrote a document for our first year students at Melbourne University who learn Haskell. The document is an introduction to most of the Haskell Prelude. It was intended as a replacement for the nice documentation that came with Miranda. It is written in latex and when formatted as ps comes out to about 28 pages long. It covers most of the functions from the Prelude with their type, definition, and example usage. Functions are listed in alphabetical order. It also covers operators in a similar way, including precedence and associativity and has a brief discussion of the class hierarchy. It is intended as a study aid. Typically our students take a printed copy with them to lab classes (yes we still print things here). Although it may be converted into HTML and presented online. It is not intended as a formal description of the Prelude, nor as a replacement for textbooks and other material. I think our students find it useful. I meant to make this public a long time ago, but I forgot about it. I was reminded today when someone requested to use it for their course in another University. So now I make it available to everyone. Please take it and use/modify for whatever purpose you like. If anyone else thinks it is a good thing then it might be nice to put on the Haskell Bookshelf at www.haskell.org. For the moment you can get the latex source (and a ps) from my web page: http://www.cs.mu.oz.au/~bjpop/papers.html I do not guarantee that everything is up to date, but feel free to fix, or notify me and I will fix it. Cheers, Bernie.

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ICLP02 FINAL CALL FOR PAPERS
by Peter Stuckey 11 Feb '02

11 Feb '02

------- Blind-Carbon-Copy X-Mailer: exmh version 2.5 10/15/1999 with version: MH 6.8.4 #1[UCI] To: pjs Subject: ICLP02 FINAL CALL FOR PAPERS Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 11 Feb 2002 11:32:42 +1100 Message-ID: <26117.1013387562(a)muldi.cs.mu.oz.au> From: Peter Stuckey <pjs(a)muldi.cs.mu.oz.au> Apologies for Receiving Multiple Copies of this Message - ---------------------------------------------------------- FINAL CALL FOR PAPERS ICLP'02 Eighteenth International Conference on Logic Programming Copenhagen, Denmark July 29th - August 1, 2002 http://floc02.diku.dk/ICLP/ ICLP'02, the Eighteenth International Conference on Logic Programming will be be held this year as part of the 2002 Federated Logic Conference (http://floc02.diku.dk/) in conjunction with CADE, CAV, FME, LICS, RTA and TABLEAUX. ICLP'02 is sponsored by IF/Prolog (http://www.ifcomputer.de) Invited Speakers include: Pierre Wolper (Universite de Liege) Stefan Decker (Stanford) TOPICS Since the first ICLP, held in Marseilles in 1982, ICLP has been the premier international conference for presenting research into logic programming. Original papers are sought in all areas of logic programming including (but not restricted to): Theory Implementation Semantic Foundations Compilation Formalisms Memory Management Non-monotonic Reasoning Virtual Machines Knowledge Representation Parallelism Language Issues Environments Constraints Program Analysis Concurrency Program Transformation Objects Validation and Verification Coordination Debugging Mobilility Higher Order Applications Types Modes Deductive Databases Programming Techniques Software Engineering Natural Language Web tools Internet Agents Artificial Intelligence Papers describing innovative applications of logic programming (in the broadest sense, e.g. including constraint programming, non-monotonic systems, etc.) are particularly sought. We welcome submission in, but not limited to, the following topics: surveys of an application area, problems to which logic programming may be applied, experience in applying logic programming, software engineering aspects of logic programming and areas where further research is required to meet industrial needs. There will be an award for the best application paper sponsored by IF/Prolog. SUBMISSION Papers must describe original, previously unpublished work, be written and presented in English, not exceed 15 pages (A4 or letter format, up to 5,000 words), and not be simultaneously submitted for publication elsewhere. The proceedings will be published by Springer Verlag in the Lecture Notes in Computer Science series. Authors are strongly encouraged to use LaTeX2e and the Springer llncs class file, available at http://www.springer.de/comp/lncs/authors.html Submission is Web-based. In order to submit a paper, authors should upload it via the web at http://www.cs.mu.oz.au/~pjs/ICLP2002/ where more detailed instructions are given. If submission through the Web is not possible, five hard copies may be sent to the program chair. Submission Agenda: Submission of papers: February 17, 2002 Notification of acceptance: April 14, 2002 Camera-ready papers due: May 14, 2002 Workshops: The following workshops will be held in conjunction with ICLP'02. August 1: CLIMA - Computational Logic In Multi-Agent Systems July 28: CLPSE - (Constraint) Logic Programming and Software Engineering July 31: LPE - Workshop on Logic Programming Environments July 27-28: NLULP - Natural Language Understanding and Logic Programming July 27: PCL - Paraconsistent Computational Logic July 27: SAVE - Specification, Analysis and Validation for Emerging Technologies in Computational Logic July 28: UNKB - Updating Non-Monotonic Knowledge Bases Conference Location: The conference will be held at the University of Copenhagen. Program Chair: Conference Chair: Peter J. Stuckey Henning Christiansen Department of Computer Science Department of Computer Science and Software Engineering Roskilde University University of Melbourne PO Box 260 3010, AUSTRALIA DK-4000 Roskilde, DENMARK Email: pjs(a)cs.mu.oz.au Email: henning(a)ruc.dk Tel: +613-8344-9155 Tel: +45 46 74 38 32 Fax: +613-9348-1184 Programme Committee: Jose Alferes, Universidade Nova de Lisboa Francisco Bueno, Universidad Polytecnica de Madrid Henning Christiansen, Roskilde University Sandro Etalle, University of Twente Francois Fages, INRIA Maurizio Gabbrielli, University of Bologna Maria Garcia de la Banda, Monash University Michael Gelfond, Texas Tech University Gopal Gupta, UT Dallas Katsumi Inoue, Kobe University Joxan Jaffar, National University of Singapore Gerda Janssens, K.U.Leuven Bharat Jayaraman, State University of New York at Buffalo Michael Leuschel, University of Southampton Michael Maher, Loyola University Chicago Dale Miller, The Pennsylvania State University Ulf Nilsson, Linkoping University Francesca Rossi, Universita' di Padova Konstantinos Sagonas, Uppsala University Christian Schulte, Universitat des Saarlandes Harald Sondergaard, University of Melbourne Francesca Toni, Imperial College London Miroslaw Truszczynski, University of Kentucky Pascal Van Hentenryck, Brown University David S. Warren, State University of New York at Stony Brook ------- End of Blind-Carbon-Copy

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RE: Simpler Fibonacci function
by Brian Berns 10 Feb '02

10 Feb '02

> The only reason the first version of fib was used in the Gentle Intro was to > demonstrate recursive stream processing... Thank you for the explanation. For reference, the fib example occurs in a section (3.4) titled "'Infinite' Data Structures", of which I believe the simpler function is also an example. There is no reference in this section to recursive stream processing (this occurs in section 4.4). In any case, as a newbie, I can tell you that I found the fib function puzzling as stated. > ...and not to show a "canonical" version of Fibonacci Nonetheless, it seems to have become the canonical version. For example, see the list of references to this version on Google: http://www.google.com/search?q=%22zip+fib+%28tail+fib%22. This is perhaps unfortunate since fib is a kind of "hello world" for Haskell and other FP languages. -- Brian

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(no subject)
by Patrick McDonnell 10 Feb '02

10 Feb '02

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what does fixST do?
by Hal Daume III 10 Feb '02

10 Feb '02

subject says it all... -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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Re: [Newbie] Programming with MArray
by Jay Cox 10 Feb '02

10 Feb '02

> Date: Fri, 8 Feb 2002 18:35:14 -0200 > From: =?iso-8859-1?Q?Jos=E9_Romildo_Malaquias?= <romildo(a)uber.com.br> > To: haskell(a)haskell.org > Subject: [Newbie] Programming with MArray > > > --82I3+IH0IqGh5yIs > Content-Type: text/plain; charset=iso-8859-1 > Content-Disposition: inline > Content-Transfer-Encoding: 8bit > > Hello. > > To learn how to program with muttable arrays in Haskell, I have done > a very simple program to sum two arrays. I am submitting it to this > group so that it can be reviewd and commented. I have not find > examples on how to program with muttable arrays. > > I would like for instance to see comments on the way the > iteration over the array indices was done: using a list > of indices. I looked for a way of incrementting an > index, starting from the lower bound towards the upper > bound, but failed in finding it. Is there other ways of > iterating over the muttable array other then using > its list of indices? > > Regards, > > Romildo in short, I dont see why you couldn't have some helper function defined in your "where" clause like: update' i = if (i > some_max_bound) then return () else do x1<- readArray v1 i x2<- readArray v2 i writeArray v3 (x1+x2) update' (succ i) I do know of papers where they write monadic functions this way so I presume it is efficient. indeed you might consider using the Bounded class for this purpose --you can do this right?? newtype Foo = F Int deriving (Eq,Enum,Ord,...) instance Bounded Foo where maxBound = F 9 minBound = F 1 In terms of arbitrary indices? If I've read the current Haskell reports right then if your type "a" doesnt have "Enum a" and (Eq "a" or Ord "a") instance, it looks like iterating over a list is the only solution. Jay Cox

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Re: Re: XSLT, Perl, Haskell, & a word on language design
by Dimitre Novatchev 09 Feb '02

09 Feb '02

On Tuesday 15 January 2002, 21:58:06, Eray Ozkural (exa) wrote: > On Wednesday 16 January 2002 04:35, Manuel M. T. Chakravarty wrote: > > > > The really bad thing is that the designers of XSLT [1.0] > > made the language free of side effects but then failed to > > include fundamental support for basic functional > > programming idioms. > > > > So, there are actually people who seriously take XSLT to be a > programming language? Interesting, as I think it is just overdoing an > already overdone > concept (hint: it's a poor ascii tree). Yes, there are such people. Actually, all the examples from John Hughes' article "Why functional programming matters" can be implemented in XSLT 1.0, as shown in the recently published article: "The Functional Programming Language XSLT" at http://www.topxml.com/xsl/articles/fp Cheers, Dimitre Novatchev. __________________________________________________ Do You Yahoo!? Send FREE Valentine eCards with Yahoo! Greetings! http://greetings.yahoo.com

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Kinds Workaround
by Ashley Yakeley 09 Feb '02

09 Feb '02

At 2002-02-08 03:36, Koen Claessen wrote: >Here, you might do the following trick: > > type HasKind_Help x dummy = x > type HasKind_Star_To_Star x = HasKind_Help x (x Int) > > type C c x y = c (HasKind_Star_To_Star x) > (HasKind_Star_To_Star y) > > type Composer c = > forall x y z . C c y z -> C c x y -> C c x z Yuck... I discovered a much simpler workaround, a class which has a parameter of kind '*': class T a where { undef :: a; -- force kind '*' }; instance T a where -- true for all types { undef = undefined; }; data (T (p Bool),T (q Bool)) => CMap0 p q = MkCMap0; type Composer c = forall x y z. (T (x Bool)) => (c y z) -> (c x y) -> (c x z); Neat, huh? Finally, a reason for allowing contexts in data type declarations! -- Ashley Yakeley, Seattle WA

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RE: efficiency question
by Konst Sushenko 09 Feb '02

09 Feb '02

> > On Friday 08 February 2002 22:14, you wrote: > > define > > > > test1 l = > > let s1 = foldr (+) 1 l > > s2 = foldr (-) 1 l > > in (s1, s2) > > > > test2 l = > > let s = foldr (\x (a,b) -> (x+a,x-b)) (1,1) l > > in s > > > > why is test1 so much faster than test2 for long lists l (eg > > [1..1000000])? replacing foldr with foldl makes it faster > (of course), > > but test2 is still much slower. > > > > i *expected* test2 to be much faster because you're only > traversing the > > list once. presumably the two elements "a" and "b" in > test2 could be put > > in registers and i'd imagine test2 should be faster (it > certainly would be > > if written in c). > > I'd say that's because in the second case you also got to > apply the (,), > besides the (+)/(-) constructor during the transversing... > Am I right? > > J.A. My guess is that it is due to the laziness of the addition/subtraction in (,)

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RE: efficiency question
by Konst Sushenko 09 Feb '02

09 Feb '02

Did you try strict +/-? In (,). I am just curious. > -----Original Message----- > From: Hal Daume III [mailto:hdaume@ISI.EDU] > Sent: Friday, February 08, 2002 3:53 PM > To: Konst Sushenko > Cc: Jorge Adriano; haskell(a)haskell.org > Subject: RE: efficiency question > > > I've tried using a strict fold: > > foldl' f a [] = a > foldl' f a (x:xs) = (foldl' f $! f a x) xs > > but that has no effect (or minimal effect). > > -- > Hal Daume III > > "Computer science is no more about computers | hdaume(a)isi.edu > than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume > > On Fri, 8 Feb 2002, Konst Sushenko wrote: > > > > > > > On Friday 08 February 2002 22:14, you wrote: > > > > define > > > > > > > > test1 l = > > > > let s1 = foldr (+) 1 l > > > > s2 = foldr (-) 1 l > > > > in (s1, s2) > > > > > > > > test2 l = > > > > let s = foldr (\x (a,b) -> (x+a,x-b)) (1,1) l > > > > in s > > > > > > > > why is test1 so much faster than test2 for long lists l (eg > > > > [1..1000000])? replacing foldr with foldl makes it faster > > > (of course), > > > > but test2 is still much slower. > > > > > > > > i *expected* test2 to be much faster because you're only > > > traversing the > > > > list once. presumably the two elements "a" and "b" in > > > test2 could be put > > > > in registers and i'd imagine test2 should be faster (it > > > certainly would be > > > > if written in c). > > > > > > I'd say that's because in the second case you also got to > > > apply the (,), > > > besides the (+)/(-) constructor during the transversing... > > > Am I right? > > > > > > J.A. > > > > My guess is that it is due to the laziness of the > addition/subtraction > > in (,) > > _______________________________________________ > > Haskell mailing list > > Haskell(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell > > > >

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