July 2003 - Haskell - Haskell.org

Unicode + Re: Reading/Writing Binary Data in Haskell
by George Russell 14 Jul '03

14 Jul '03

Martin quoted Glynn: > OTOH, existing implementations (at least GHC and Hugs) currently read > and write "8-bit binary", i.e. characters 0-255 get read and written > "as-is" and anything else breaks, and changing that would probably > break a fair amount of existing code. The binary library I posted to the libraries list: http://haskell.org/pipermail/libraries/2003-June/001227.html which is for GHC, does this properly. All characters are encoded using a standard encoding for unsigned integers, which uses the bottom 7 bits of each character as data, and the top bit to signal that the encoding is not yet complete. Characters 0-127 (which include the standard ASCII ones) get encoded as themselves. This is probably not nearly as efficient as encoding characters as themselves, but it's nice to be Unicode-proof ...

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Reading/Writing Binary Data in Haskell
by Gordon James Miller 13 Jul '03

13 Jul '03

Hello to all, I'm recently working on doing some atmospheric modelling for my PhD thesis work and I've been writing parallel implementations in Java, Ruby, and Haskell. I picked up Haskell as part of the LoTY project and was especially impressed by how expressive and clean the code is. I've been quite successful at writing most of my numerical libraries in Haskell (typically at a much reduced SLOC) but I'm not butting my head against binary data. I have a large store of data, output by a Fortran model, which essentially consists of binary files containing arrays of floating point values. In doing some googling on reading binary data in Haskell I've come across some old (> 1 year) references to some mailing list discussions on reading binary data. So given the background I have a few questions: 1 - Is there yet a standard, or at least commonly supported by hugs and ghc, method for dealing with binary data. 2 - If not, is there a "standard" library that is used to manipulate binary data. I've seen some references to some implementations but given that this is being done in my limited spare time (I'm not a full time student) I'd rather not spin my wheels on something that's going to be dead in a matter of months. 3 - What is the current status of getting binary data into the Haskell standard? I understand that I can write a C extension, but part of my interest in Haskell lies in the ability to write scientific software that very closely resembles the mathematics that are being modelled. On that note, I'd also be very interested in conversing with people that are doing physics modelling (atmospheric dynamics and chemistry is esp. interesting) using functional languages. Thanks! Gordon Miller gmiller(a)bittwiddlers.com

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Re: How overload operator in Haskell?
by Liu Junfeng 12 Jul '03

12 Jul '03

I come up a solution as this: --------------------------------------------------- module Vector where data Vector =Vector [Double] fromVector :: Vector -> [Double] fromVector (Vector v) = v fromList :: [Double] -> Vector fromList v = Vector v toVector :: Double -> Vector toVector x = Vector (repeat x) instance Eq Vector where v1 ==v2 = (fromVector v1) == (fromVector v2) instance Show Vector where show v = show (fromVector v) instance Num Vector where v1 + v2 =Vector (zipWith (+) (fromVector v1) (fromVector v2)) v1 - v2 =Vector (zipWith (-) (fromVector v1) (fromVector v2)) v1 * v2 =Vector (zipWith (*) (fromVector v1) (fromVector v2)) signum v = Vector (map signum (fromVector v)) abs v = Vector ((repeat.sqrt.sum.fromVector) (v*v)) fromInteger n =Vector (repeat (fromInteger n)) instance Fractional Vector where v1 / v2 = Vector (zipWith (/) (fromVector v1) (fromVector v2)) fromRational r =Vector (repeat (fromRational r)) -------------------------------------------------------------------------- rk4 :: ((Vector,Vector)->Vector)->Vector->Vector->Vector->[Vector] rk4 _ _ _ (Vector []) = [] rk4 f h y0 (Vector (x0:xs)) = y0 :rk4 f h y1 (Vector xs) where y1=yp f h (toVector x0) y0 yp ::((Vector,Vector)->Vector)->Vector->Vector->Vector->Vector yp f h x y = y + (k1 + 2 * (k2 + k3) + k4) where k1=h*f(x,y) k2=h*f(x+0.5*h, y +(0.5*k1)) k3=h*f(x+0.5*h, y +(0.5*k2)) k4=h*f(x+h, y+k3) a=let g (x,y1) = y1 x0 = 0 h = 0.01 x =Vector [x0,x0+h..3] y0 =Vector [0,0.5] in rk4 g (toVector h) y0 x -------------------------------------------------------------------------- The main problem is how to make type convert implicitly. Whem a function needs a vector as its parameter, pass a double and it is converted to vector implicitly. ======= 2003-07-12 12:18:00 Jon Fairbairn Wrote��======= >On 2003-07-12 at 20:20+1000 Andrew J Bromage wrote: >> G'day all. >> >> On Fri, Jul 11, 2003 at 04:28:19PM -0400, Dylan Thurston wrote: >> >> > Don't be silly [...] >> >> Never! > >Or only sometimes. I'm surprised that no-one has yet >answered the question "How overload operator in Haskell?" >with "Overload operator in Haskell fine". (cf Cary Grant) I am also surprised at this, it can be done by C++ . > >-- >J�n Fairbairn Jon.Fairbairn(a)cl.cam.ac.uk >31 Chalmers Road jf(a)cl.cam.ac.uk >Cambridge CB1 3SZ +44 1223 570179 (after 14:00 only, please!) > > >_______________________________________________ >Haskell mailing list >Haskell(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell = = = = = = = = = = = = = = = = = = = = Regards, Liu Junfeng liujf(a)softhome.net 2003-07-12

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.hi files
by Arun Kumar S Jadhav 11 Jul '03

11 Jul '03

Hi all, Can any one tell me what is the use of .hi (interface) files. I want to know the steps involved in the compilation of a .hs file. I went thru the what nhc98 roughly does and saw that it generates interface file for each module. Please enlighten as to what is the precise function of interface files. Regards, -- Arun Kumar S Jadhav Masters Student, SIC-309, KReSIT, IIT-Bombay, India Ph: +91-22-25764967 http://www.it.iitb.ac.in/~arunk ***************************** Never negotiate out of fear Never fear to negotiate *****************************

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CFP: CLIMA IV - 4th Intl. Workshop on Computational Logic in Multi-Agent Systems
by João Alexandre Leite 11 Jul '03

11 Jul '03

========================================================================== FIRST CALL FOR PAPERS CLIMA IV Fourth International Workshop on Computational Logic in Multi-Agent Systems January 6-7, 2004, Fort Lauderdale, Florida, USA http://centria.di.fct.unl.pt/~jleite/climaIV/index.htm Post-Proceedings will be published in Springer Verlag LNAI Submission Deadline: September 19th Co-located with the 7th LPNMR and the 8th AIMATH =========================================================================== Over recent years, the notion of agency has claimed a major role in defining the trends of modern research. Influencing a broad spectrum of disciplines such as Sociology, Psychology, Philosophy and many more, the agent paradigm virtually invaded every sub-field of Computer Science, not least because of the Internet and Robotics. Multi-agent Systems (MAS) are communities of problem-solving entities that can perceive and act upon their environments to achieve their individual goals as well as joint goals. The work on such systems integrates many technologies and concepts in artificial intelligence and other areas of computing. There is a full spectrum of MAS applications that have been and are being developed; from search engines, educational aids to electronic commerce and trade. Although commonly implemented by means of imperative languages, mainly for reasons of efficiency, the agent concept has recently increased its influence in the research and development of computational logic based systems. Computational Logic, by virtue of its nature both in substance and method, provides a well-defined, general, and rigorous framework for systematically studying computation, be it syntax, semantics, procedures, or implementations, environments, tools, and standards. The purpose of this workshop is to discuss techniques, based on computational logic, for representing, programming and reasoning about multi-agent systems in a formal way. This is clearly a major challenge for computational logic, to deal with real world issues and applications. Following the workshop on Multi-Agent Systems in Logic Programming affiliated with ICLP'99, the first CLIMA workshop took place in London, UK, affiliated with CL'2000. The 2001 edition of CLIMA, took place in Paphos, Cyprus, affiliated with ICLP'01. CLIMA'02 took place in Copenhagen, Denmark, and was affiliated with ICLP'02 and part of FLOC'02. We solicit unpublished papers that address formal approaches to multi-agent systems. The approaches as well asbeing formal must make a significant contribution to the practice of multi-agent systems. Relevant techniques include, but are not limited to, the following: * Nonmonotonic reasoning in MAS * Planning under incomplete information in MAS * Logical foundations of MAS * Usage of abduction in MAS * Representation of knowledge and belief in MAS * Knowledge and belief updates in MAS * Temporal reasoning for MAS * Theory of argumentation for MAS * Negotiation and co-operation for MAS * Communication languages for MAS * Distributed constraint satisfaction in MAS * Modal logic approaches to MAS * Logic based programming languages for MAS * Distributed theorem proving for MAS * Logic based implementations of MAS * Decision theory for MAS * Logic based agents for the Internet SUBMISSION INSTRUCTIONS We welcome and encourage the submission of high quality, original papers, which are not simultaneously submitted for publication elsewhere. Please refer to the workshop web pages for further instructions concerning the submission procedures. IMPORTANT DATES * Submission: September 19th, 2003 * Notification of Acceptance: October 17th, 2003 * Final version due: November 13th, 2003 * CLIMA IV: January 6-7th, 2004 PROCEEDINGS Post-proceedings will be published by Springer-Verlag as a volume of the Lecture Notes on Artificial Intelligence (LNAI) series. Informal proceedings will be available at the workshop and online. PROGRAM COMMITTEE * Chitta Baral, Arizona State University, USA * Gerd Brewka, University of Leipzig, Germany * Jürgen Dix, The University of Manchester, UK * Thomas Eiter, Vienna University of Technology, Austria * Klaus Fischer, DFKI, Germany * Michael Fisher, University of Liverpool, UK * James Harland, Royal Melbourne Inst. of Tech., Australia * Katsumi Inoue, Kobe University, Japan * Gerhard Lakemeyer, Aachen Univ. of Technology, Germany * João Leite, New University of Lisbon, Portugal * Yves Lespérance, York University, Canada * John Jules Ch. Meyer, Univ. of Utrecht, The Netherlands * Leora Morgenstern, IBM, USA * Luís Moniz Pereira, New University of Lisbon, Portugal * Fariba Sadri, Imperial College, UK * Ken Satoh, National Institute of Informatics, Japan * Renate Schmidt, The University of Manchester, UK * Guillermo Simari, Universidad Nacional del Sur, Argentina * V. S. Subrahmanian, University of Maryland, USA * Francesca Toni, Imperial College, UK * Paolo Torroni, University of Bologna, Italy * Wiebe van der Hoek, University of Liverpool, UK * Cees Witteveen, Delft Univ. of Tech., The Netherlands WORKSHOP ORGANIZERS: * Jürgen Dix, The University of Manchester, UK (dix(a)cs.man.ac.uk) * João Leite, New University of Lisbon, Portugal (jleite(a)di.fct.unl.pt) INQUIRIES: Please send program suggestions and inquires to either of the organizers.

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constructors in O'Haskell
by Peter Padawitz 11 Jul '03

11 Jul '03

How may I hide constructors in O'Haskell 'cause export lists don't work in this language? Peter

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Monad constructors
by Peter Padawitz 11 Jul '03

11 Jul '03

Why must every Monad instance be a datatype or newtype, even if there will be just a single constructor? Peter

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RE: How overload operator in Haskell?
by Hal Daume 09 Jul '03

09 Jul '03

Quite right :). I agree whole-heartedly. There's nothing wrong with overloading (+) and (-) in this case, but the rest really don't make much sense. Probably best to leave them undefined and just not use them. Then you could define your own dot product function and the like. -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: haskell-admin(a)haskell.org > [mailto:haskell-admin@haskell.org] On Behalf Of Jerzy Karczmarczuk > Sent: Wednesday, July 09, 2003 8:25 AM > To: haskell(a)haskell.org > Subject: Re: How overload operator in Haskell? While this is a possible solution, I would shout loudly: "Arrest this man, he is disrespectful wrt math!". Actually, this shows once more that the Num class and its relatives is a horror... Signum in this context has no sense. The multiplication might be the cross product, but its anti-commutativity shows plainly that this is not a 'standard' multiplication. 'fromInteger' has even less sense than signum... I am particularly horrified by "abs v = map abs v", and I am sure all of you see why. I think that a more sane solution would be the definition of a particular class with operations porting names like <+>, or ^+^, or whatever similar to standard ones, but different. Jerzy Karczmarczuk _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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RE: Reading/Writing Binary Data in Haskell
by Hal Daume 09 Jul '03

09 Jul '03

GHC uses its own version of the NHC library. It's linked off of the libraries page: http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne/haskell_libs /Binary.html Moreover, I have my own version of this library which we were, for a while, trying to synch with the NHC library so it could become standard. This is available at: http://www.isi.edu/~hdaume/haskell/NewBinary/ and allows both bit-based and byte-based writing styles. -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: haskell-admin(a)haskell.org > [mailto:haskell-admin@haskell.org] On Behalf Of Christian Maeder > Sent: Wednesday, July 09, 2003 1:34 AM > To: The Haskell Mailing List > Subject: Re: Reading/Writing Binary Data in Haskell > > > >>There isn't a standard mechanism for binary I/O. > > > > > > NHC98 contains the York Binary library. Can someone tell me > if this is > > available for other Haskell systems? And didn't GHC also > provide binary I/O? > > How does the GHC itself read/write binary data, since the interface > files (*.hi) produced by GHC are in a binary format? (Whereas > NHC98 *.hi > are text files.) > > Christian > > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell >

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How overload operator in Haskell?
by Liu Junfeng 09 Jul '03

09 Jul '03

I've learned haskell months, but I still can't understand the type system very well. I can only write: ----------------------------------- type Vector = [Double] vadd,vsub :: Vector->Vector->Vector v1 `vadd` v2 = zipWith (+) v1 v2 v1 `vsub` v2 = zipWith (-) v1 v2 svmul :: Double->Vector->Vector s `svmul` v = map (s*) v ------------------------------------ Tough it works, it is not convenient to use. How to create a Vector type and overload mathematical operators? Thanks for your help. Liu Junfeng liujf(a)softhome.net

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