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Re: gcd 0 0 = 0
by George Russell 18 Dec '01

18 Dec '01

I've reconsidered my earlier position and think now that the Prelude is wrong to make gcd 0 0 an error, and should return 0. It probably doesn't make much difference to anyone, but it's like 1 not being a prime; it may be slightly harder to explain, but it makes the maths come out nicer and is in the end a simplification.

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4th Int'l Symp.: Practical Aspects of Declarative Languages
by Dr. Gopal Gupta 17 Dec '01

17 Dec '01

[ o Apologies for multiple messages. o Please register and make hotel reservations as soon as possible since both deadlines are approaching fast (Dec. 27th) ]. You are cordially invited to the Fourth International Symposium on Practical Aspects of Declarative Languages that will be held on Jan 19-20, 2002 right after ACM POPL. The program includes invited talks by three distinguished speakers: J. Strother Moore of the University of Texas at Austin, Catherine Meadows of the Naval Research Labs, and Veronica Dahl of Simon Fraser University. Very low registration rates ($150 regular and $100 student) and low conference hotel rates have been secured to make the event affordable. The program ends by late afternoon on Sunday to let attendees return home on Sunday itself. If you are attending ACM POPL, we especially encourage you to plan to attend PADL. More details can be found at: http://www.cs.sunysb.edu/~padl2002 --------------------------------------------------------------------- Fourth International Symposium on Practical Aspects of Declarative Languages (PADL '02) Portland, Oregon, USA Jan 19-20, 2002 Co-located with POPL 2002 --------------------------------------------------------------------- Conference Program ================== Jan 19th 8:45-9:00 Opening Remarks 9:00-10:00 Invited Talk #1 Using a Declarative Language to Build an Experimental Analysis Tool Catherine Meadows (Naval Research Laboratory), 10:00-10:30 Coffee Break 10:30-12:30 Session-I: Modeling Engineering Structures using Constrained Objects Bharat Jayaraman and Pallavi Tambay Compiler Construction in Higher Order Logic Programming Chuck Liang Declarative Programming with Application to Clinical Medicine: On the Use of Gisela in the MedView Project. Olof Torgersson Semantics-based Filtering: Logic Programming's Killer App? Gopal Gupta, Hai-Feng Guo, Arthur Karshmer, Enrico Pontelli, Desh Ranjan, B. Milligan, N. Datta, O. El Khatib, M. Noamany, and X. Zhou 12:30-1:30 Lunch 1:30-2:30 Invited Talk #2 How to Talk to Your Computer So That it Will Listen Veronica Dahl (Simon Fraser University), 2:45-4:15 Session-II: Linear Scan Register Allocation in a High-Performance Erlang Compiler Erik Johansson and Konstantinos Sagonas Typed Combinators for Generic Traversal Ralf Laemmel and Joost Visser Event-Driven FRP. Zhanyong Wan, Walid Taha, and Paul Hudak 4:15-4:30 Coffee Break 4:30-6:00 Session-III: Compiling Embedded Programs to Byte Code. Morten Rhiger, Exploiting Efficient Control and Data Structures in Logic Programs. Rong Yang and Steve Gregory, Memory Management and Scheduling in a Tabling Engine Luis F. Castro and Terrance Swift and David S. Warren -------------------------------------------------------------------------------- Jan 20th 9:00-10:00 Invited Talk #3: Single-Threaded Objects in ACL2. J. Strother Moore (University of Texas, Austin) 10:00-10:30 Coffee Break 10:30-12:30 Session-IV: Adding Apples and Oranges Martin Erwig and Margaret Burnett WASH/CGI: Server-side Web Scripting with Sessions and Typed, Compositional Forms. Peter Thiemann A better XML parser through functional programming. Oleg Kiselyov Functional Approach to Texture Generation. Jerzy Karczmarczuk 12:30-1:30 Lunch 1:30-3:30 Session-V: Abstract Interpretation over Non-Deterministic Finite Tree Automata for Set-Based Analysis of Logic Programs. John Gallagher, German Puebla, A High-Level Generic Interface to External Programming Languages for ECLiPSe. Kish Shen, Joachim Schimpf, Stefano Novello, Josh Singer, Segment Order Preserving and Generational Garbage Collection for Prolog. Ruben Vandeginste, Konstantinos Sagonas, and Bart Demoen, A Debugging Scheme for Declarative Equation Based Modeling Languages. Peter Bunus, Peter Fritzson

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faculty position in logic
by LICS 17 Dec '01

17 Dec '01

[Sincere apologies for duplicates] Indiana University invites applications for a tenure-track assistant professor position in applied logic. Please see www.informatics.indiana.edu/positions/logic.html for details. Applications received within the next few weeks are likely to still get full consideration. Applicants are welcome to email to foc(a)cs.indiana.edu to notify of their mailed application, and to provide pointers to any pertinent on-line documentation.

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faculty position in logic
by LICS 17 Dec '01

17 Dec '01

[Sincere apologies for duplicates] Indiana University invites applications for a tenure-track assistant professor position in applied logic. Please see www.informatics.indiana.edu/positions/logic.html for details. Applications received within the next few weeks are likely to still get full consideration. Applicants are welcome to email to foc(a)cs.indiana.edu to notify of their mailed application, and to provide pointers to any pertinent on-line documentation.

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RE: Confused about default
by Simon Peyton-Jones 17 Dec '01

17 Dec '01

Well, Foo *is* an instance of Num, so a correct Haskell impl should pick that instance always. Since you don't define the fromInteger method in the instance decl, you get a runtime error. I don't know what you expect the [Foo] and Foo -> Int defaults to do. GHCi fails to put the correct default decl in place for command-line expressions. This is a known bug which we have not got around to fixing yet Simon | -----Original Message----- | From: Ian Lynagh [mailto:igloo@earth.li] | Sent: 14 December 2001 21:29 | To: haskell(a)haskell.org | Subject: Confused about default | | | | Hi all | | I am rather confused about default. | | In section 4.3.4 the report says | "each ti must be a monotype for which Num ti holds" | but according to grep this is the only place "monotype" | appears in the report. | | If I have the module | | module TT (Foo(..)) where | | default (Foo, [Foo], Foo -> Int) | | data Foo = Foo deriving (Eq, Show) | | instance Num Foo where {} | instance (Eq a, Show a) => Num [a] where {} | instance Eq (a -> b) where {} | instance Show (a -> b) where {} | instance Num (a -> b) where {} | | then hugs accepts it and | TT> 5 | | Program error: Undefined member: fromInteger | | ghc accepts it and | TT> 5 | 5 | | nhc tells me | | Error when renaming:: | Illegal type in default at 4:17 | | If I remove all the list and function stuff then hi says | TT> 5 | 5 | | If I have a | main = putStrLn $ show 5 | | then nhc gives me | TT> main | No default definition for class method fromInteger | | and ghci gives me | Main> main | *** Exception: TT.lhs:8: No instance nor default method for class | operation PrelNum.fromInteger | | | It seems to me that hugs is in the right with it's handling | of 5, but I am not sure who is wrong with default ([Foo]) or | (Foo -> Int). | | | Finally, the context free grammar doesn't currently enforce | the restriction that only one default declaration be given. | Fixing it would make rather a mess, though. | | | Ian | | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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Call for Applications to PhD Positions, Chalmers University, Sweden
by Reiner Haehnle 17 Dec '01

17 Dec '01

Please pass on to interested students. Apologies for multiple copies. --------------------------------------------------------------------- New PhD Positions (DEADLINE 15 February 2002! See "How to apply" below) Department of Computing Science, Chalmers University of Technology & University of Gothenburg Sweden The Department has about 70 researchers, half being faculty members and half PhD students. Our focus is on programming logic, type theory, functional programming, formal methods, distributed and concurrent systems, security, algorithms, bioinformatics, human computer interaction, and computational linguistics, but research is not restricted to these topics. For more information, see http://www.cs.chalmers.se/Cs/Research. PhD positions are for 5 years. There is no tuition fee. A PhD position is a regular job with social benefits; the salary amounts currently to about 16700 SEK per month in the first year (the exact amount depends on teaching duties, usually 20% of your time). Knowledge of Swedish is not a prerequisite for application. English is our working language for research. Both Swedish and English are used in undergraduate courses. Half of our researchers and PhD students are native Swedes; the rest come from more than 20 different countries. Applicants must have a very good undergraduate degree in Computing Science or in a related subject with a strong Computing Science component. They must also have a strong interest in doing research. You may even apply if you have not yet completed your degree, but expect to do so by September 2002. You are also invited to apply for our new International Master's Programme in Dependable Computer Systems, which can help you to obtain the necessary qualification (see http://www.cs.chalmers.se/Cs/Education/dcs/) The School especially welcomes female applicants. How to apply ------------ First, immediately register your intention to apply using the electronic application form on the WWW via http://www.md.chalmers.se/Jobs/PhD/phd-02-en.thtml The full application should contain 1 A letter of application, listing specific research interests 2 A curriculum vitae 3 Attested copies of degrees and other certificates 4 Copies of relevant work, for example dissertations or articles, that you have authored or co-authored 5 A description of: a previous teaching experience, documented b previous PhD studies, also in other subjects; state financial support for these, if any c previous work experience 6 Letters of recommendation from your teachers or employers If you have financial support of your own (industry job, grant, etc.), please state this fact clearly. It will increase your chances to be accepted considerably, because you need not compete for the limited number of fully financed positions. Send your full application (paper mail) to Department of Computing Science School of Computer Science and Engineering Chalmers University of Technology 412 96 Gothenburg Sweden to arrive by 15 February 2002. You will know the result of your application by 1 May 2002.

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space efficiency question
by Frank Dellaert 17 Dec '01

17 Dec '01

I'm not a compiler/interpreter implementer, just a Haskell user :-) My question is: if I have two datatypes, say newtype Attributes = Att [String] data Instance = Instance Attributes [Int] where an Attributes value describes the discrete attributes that are stored (as Int) in an Instance. Now: if I have a couple of thousand of these Instances, created with the same Attributes value, as in: a = Attributes ["a","bc"] i0000 = Instance a [1,2] i0001 = Instance a [1,1] ... i7896 = Instance a [2,1] can I be assured that there are not thousands of actual copies of a but that they simply have a pointer to a ? I'm interested in the answer for both ghc (compiled/interpreted) as interpreted Hugs. I would hope, so, right ? Is there an actual guarantee or is that an optimization that the implementation might or might not implement ? Cheers Frank Dellaert

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Re: ANNOUNCE: GCJNI - Java Native Interface for Haskell
by Ashley Yakeley 17 Dec '01

17 Dec '01

At 2001-12-16 12:53, Antony Courtney wrote: >I am pleased to announce an experimental release of GCJNI. Eh, you beat me to a first release, which I was going to announce yesterday, but SourceForge's file release system is currently broken. I guess I'll have to put it on semantic.org I had no idea anyone else was working on this. Nevertheless, I suspect I'm further along. -- Ashley Yakeley, Seattle WA

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ANN: Release 0.1 of Haskell/Java VM Bridge
by Ashley Yakeley 17 Dec '01

17 Dec '01

The first release, 0.1, of Haskell/Java VM Bridge is now available. Haskell/Java VM Bridge allows Haskell programs access to the Java Virtual Machine. Features include: * On-the-fly creation of Java classes with Haskell functions for methods. * Lifted monads which do all the necessary JNI preloading and 'env'-pointer variable handling for you. These can be automatically generated via a tool (MakeJVMModule). * Integration of garbage collectors, type-class based overloading, and a tool (MakeClassModule) which uses Java reflection etc. to generate a Haskell module etc., etc. It is, however, only available for Unix and works only with GHC. This release should be 'beta' quality, but has undergone little testing. You will need: An x86 machine running some form of Unix; GHC 5.02 or later; The appropriate JVM, installed in the appropriate place: - IBM JDK/JRE 1.3 for x86, installed in /usr/lib/ibm-java/IBMJava2-13/ - Blackdown Port of Sun's JRE 1.3/Sun JDK 1.3 for x86, installed in /usr/lib/j2sdk1.3/ and /usr/lib/j2re1.3/ No documentation is currently available, sorry. Two examples have been included: a trivial "hello world" program, and a program that shows a Java Frame containing an instance of a Haskell-defined subclass of Canvas that has a Haskell 'paint' method that draws an oval. You should be able to figure out most of it from that... and of course the source is available from SourceForge CVS. Be sure to download the correct .tar.gz file for your Java VM. Simple installation instructions are included in the file. <http://semantic.org/jvm-bridge/haskell-jvm-bridge-1_3.IBM.classic-0.1.i686 .tar.gz> <http://semantic.org/jvm-bridge/haskell-jvm-bridge-1_3.Blackdown.classic.na tive_threads-0.1.i686.tar.gz> SourceForge's file release system is currently broken. When it's fixed, I'll put it there too. Haskell/JVM Bridge and source code is licensed under the GNU Lesser GPL. <http://sourceforge.net/projects/jvm-bridge/> I hope to build an Darwin/OS X version just as soon as there's a port of GHC 5.02 with a working createAdjustor. -- Ashley Yakeley, Seattle WA

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ANNOUNCE: Haven - Scalable Vector Graphics for Haskell
by Antony Courtney 16 Dec '01

16 Dec '01

I am pleased to announce an experimental release of Haven, a library for scalable vector graphics in Haskell. Haven provides a wealth of features, including: - Data types for common geometric shapes such as rectangles, ellipses and Bezier curves. - Composition of arbitrary shapes from sequences of straight and curved segments. - Intersection tests and bounds calculations on shapes. - Cropping of any image by any shape. - Affine transformations on images and paths. - Calculation of precise rectangular bounds of shapes and images. - High quality, anti-aliased rendering. - Scalable outline fonts. - Smooth blending of colors (gradients) - Alpha blending (transparency). - Fine-grained control of stroke width, join rules and end caps. - Constructive Area Geometry (CAG) for composing shapes using simple set-theoretic operations. Haven presents a purely functional API, but is implemented using the Java2D renderer. For more information on Haven, including examples and download instructions, please visit the haven web page at: http://www.haskell.org/haven Please send suggestions and bug reports to: antony(a)apocalypse.org Enjoy! -- Antony Courtney Grad. Student, Dept. of Computer Science, Yale University antony(a)apocalypse.org http://www.apocalypse.org/pub/u/antony

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