- Haskell-Cafe - Haskell.org

Don't play with your monads...
by David Leimbach 15 May '09

15 May '09

eventually you'll go bind. Sorry couldn't resist.

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I have forgotten .. my bad
by Vasili I. Galchin 15 May '09

15 May '09

Hello, darcs get --init ....?????? I want to pull down Data.FiniteMap. I have forgotten the path to Hackage .. I tried .... sudo darcs get http://hackage.haskell.org/ Data.FiniteMap [sudo] password for vigalchin: Invalid repository: http://hackage.haskell.org darcs failed: Failed to download URL http://hackage.haskell.org/_darcs/inventory : HTTP error (404?) ?? Obviously the code I am cabalizing needs to be "upgraded"(i.e. not using deprecated packages) but first I want it to build! Thanks, Vasili

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TFM09: Last CFP (Formal Methods Week, Eindhoven, November 6th 2009)
by J.N. Oliveira 15 May '09

15 May '09

TFM2009 2nd Int. FME Conference on Teaching Formal Methods "Widening Access to Formal Methods" Friday, November 6th 2009, co-located with FM2009 : 16th International Symposium on Formal Methods Eindhoven, the Netherlands, November 2 - November 6, 2009 CALL FOR PAPERS (URL: http://www.di.uminho.pt/tfm09) 1. About the conference ----------------------- Ten years after the First World Formal Methods Congress (FM'99) in Toulouse, formal methods communities from all over the world will once again have an opportunity to come together. As part of the First Formal Methods Week event surrounding the FM2009 conference in Eindhoven, Formal Methods Europe will be organizing TFM2009, the Second International Conference on Teaching Formal Methods. The conference will serve as a forum to explore the successes and failures of Formal Methods (FM) education, and to promote cooperative projects to further education and training in FMs. We would like to provide a forum for lecturers, teachers, and industrial partners to discuss their experience, present their pedagogical methodologies, and explore best practices. TFM2009 follows in a series of recent events on teaching formal methods, including: two BCS-FACS TFM workshops (Oxford in 2003, and London in 2006), the TFM 2004 conference in Ghent (with proceedings published as Springer LNCS Volume 3294), the FM-Ed 2006 workshop (Hamilton, co-located with FM'06), FORMED (Budapest, at ETAPS 2008), FMET 2008 (Kitakyushu 2008, co-located with ICFEM), etc. 2. Topics of interest --------------------- Formal methods (FM) have an important role to play in the development of complex computing systems - a role acknowledged in industrial standards such as IEC 61508 and ISO/IEC 15408, and in the increasing use of precise modeling notations, semantic markup languages, and model-driven techniques. There is a growing need for software engineers who can work effectively with simple, mathematical abstractions, and with practical notions of inference and proof. However, there is little clear guidance ? for educators, for managers, or for the engineers themselves ? as to what might comprise a basic education in FM. Neither the present IEEE/ACM Software Engineering Body of Knowledge (SWEBOK) nor the forthcoming Graduate Software Engineering Reference Curriculum (GSWERC) provide the kind of specific information that teachers and practitioners need to establish an adequate, balanced programme of learning in FM. Original contributions are solicited that provide insight, opinions, and suggestions for courses of action regarding the teaching FMs, including but not limited to the following aspects: * experiences of teaching FMs, both successful and unsuccessful; * educational resources including the use of books, case studies and the internet; * the education of weak and mathphobic students; * the integration, or otherwise, of FMs into the curriculum, including contributions to the definition of a Formal Methods Body of Knowledge (FMBOK); * the advantages of FM-trained graduates in the workplace; * changing attitudes towards FMs in students, academic staff and practitioners; * the necessary mathematical background. The conference proceedings will be published by Springer-Verlag in the LNCS series. Submissions may be up to 20 pages long using Springer's LNCS format. 3. Important dates ------------------ Please put the following dates in your diary: Submission deadline May 25, 2009 Notification of acceptance July 6, 2009 Final version August 3, 2009 4. How to submit ---------------- Papers for TFM2009 will be processed through the EasyChair conference management system.To submit your paper, please visit: http://www.easychair.org/conferences/?conf=tfm2009 5. Invited speakers ------------------- To be announced 6. Programme Committee ---------------------- Izzat Alsmadi (North Dakota State University, USA) Dines Bjorner (IIMM Institute, Denmark) Eerke Boiten (University of Kent, UK) Raymond Boute (Universiteit Gent, Belgium) Andrew Butterfield (Trinity College, Dublin) Jim Davies (University of Oxford, UK) David Duce (Oxford Brookes University, UK) John Fitzgerald (University of Newcastle upon Tyne, UK) Jeremy Gibbons (University of Oxford, UK) Randolph Johnson (National Security Agency, USA) Michael Mac an Airchinnigh (Trinity College, Dublin) Dino Mandrioli (Politecnico di Milano, Italy) Jose Oliveira (Universidade do Minho, Portugal) Kees Pronk (Technische Universiteit Delft, NL) Bernhard Schaetz (Tecnical University of Munique, Germany) Wolfgang Schreiner (Johannes Kepler University Linz, Austria) Simao Melo de Sousa (Universidade da Beira Interior, Portugal) Kenji Taguchi (National Institute of Informatics, Japan) Jeannette Wing (Carnegie-Mellon University, USA) 7. Sponsorship ---------------------- TFM2009 is supported by FME, the Formal Methods Europe Association

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Re: Data.Binary and little endian encoding
by John Lato 15 May '09

15 May '09

leimy2k: > On Thu, May 14, 2009 at 8:46 PM, Don Stewart <dons(a)galois.com> wrote: > >> leimy2k: >> > >> > >> > On Thu, May 14, 2009 at 8:40 PM, Don Stewart <dons(a)galois.com> wrote: >> > >> > leimy2k: >> > > I actually need little endian encoding... wondering if anyone else >> hit >> > this >> > > with Data.Binary. (because I'm working with Bell Lab's 9P protocol >> which >> > does >> > > encode things on the network in little-endian order). >> > > >> > > Anyone got some "tricks" for this? >> > >> > Yes! >> > There are big, little and host-endian primitives in the Get/Put >> monads. >> > >> > >> http://hackage.haskell.org/packages/archive/binary/0.5.0.1/doc/html/ >> > Data-Binary-Put.html#v%3AputWord16le >> > >> > You can use these to build encoders directly. >> > >> > >> > Cool... I just have to write my own encoder and decoder now. >> > >> > As a request could we get encodeLe decodeLe for a later version of this >> > library? :-) That'd be totally awesome. >> >> Oh, you mean entirely different instances for all the current ones, that >> use LE encodings? >> > > Well the library is leaning towards "Network Byte Order" in that it has > encode/decode that only encode/decode for Big Endian. > > Us folks who have to do little endian all now have to write our own > encoding/decoding :-) > > I'm speaking specifically of the encode/decode functions. I have no idea > how they're implemented. The encode/decode functions just call the runGet/runPut functions for whatever is being encoded or decoded to combined with the get/put functions from the Binary instance. The endian-ness is entirely determined by the Binary instance for the data type you're encoding/decoding, not anything in the encode/decode functions themselves. For data types you define, you can make the Binary instance LE standard (although it may not be a good idea) by using the little-endian primitives Don mentioned. For built-in types, if you want to use a different endian-ness, you can make new get/put functions then call runGet/runPut on those directly. You won't be able to redefine the Binary instances, but if you'll be doing this with a lot of different types you could make your own BinaryLE class like this: class BinaryLE t where putLE :: t -> Put getLE :: Get t encodeLE :: BinaryLE a => a -> ByteString encodeLE = runPut . putLE decodeLE :: BinaryLE a => ByteString -> a decodeLE = runGet getLE I've done some work with Binary and little-endian, and this bias never really bothered me (I think it's actually a host-endian bias, could be mistaken). I was using my own data types so I had to make my own custom Binary instances, which I would have had to do anyway. The data format specified little-endian, so making the Binary instance LE-standard seemed appropriate. You'd only need to re-make custom get/put functions if you're using types that already have Binary instances, and you intend to manipulate the data outside of Haskell. Does that describe your situation? John

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ICFP09 Accepted Papers
by Matthew Fluet (ICFP Publicity Chair) 15 May '09

15 May '09

Accepted Papers ICFP 2009: International Conference on Functional Programming Edinburgh, Scotland, 31 August - 2 September 2009 http://www.cs.nott.ac.uk/~gmh/icfp09.html The ICFP 2009 Program Chair and Committee are pleased to announce that the following papers have been accepted for the conference. Additional information regarding the final program, invited speakers, and registration will be forthcoming. However, the Local Arrangements Co-Chairs would like to remind participants of the following: * ICFP'09 coincides with the final week of the Edinburgh International Festival, one of the premier arts and cultural festivals in the world. The opportunity to attend the Festival is a plus! Due to the popularity of Edinburgh during the festival period, we recommend booking accommodation early. More details regarding accommodation may be obtained from the ICFP 2009 Local Arrangements webpage: http://www.haskell.org/haskellwiki/ICFP_2009_Local_Arrangements Accepted papers ~~~~~~~~~~~~~~~ A CONCURRENT ML LIBRARY IN CONCURRENT HASKELL Avik Chaudhuri A THEORY OF TYPED COERCIONS AND ITS APPLICATIONS Nikhil Swamy, Michael Hicks and Gavin Bierman A UNIVERSE OF BINDING AND COMPUTATION Daniel Licata and Robert Harper ATTRIBUTE GRAMMARS FLY FIRST-CLASS: HOW TO DO ASPECT ORIENTED PROGRAMMING IN HASKELL Marcos Viera, S. Doaitse Swierstra and Wouter S. Swierstra AUTOMATICALLY RESTFUL WEB APPLICATIONS OR, MARKING MODULAR SERIALIZABLE CONTINUATIONS Jay McCarthy BEAUTIFUL DIFFERENTIATION Conal Elliott BIORTHOGONALITY, STEP-INDEXING AND COMPILER CORRECTNESS Nick Benton and Chung-Kil Hur CAUSAL COMMUTATIVE ARROWS AND THEIR OPTIMIZATION Hai Liu, Eric Cheng and Paul Hudak COMPLETE AND DECIDABLE TYPE INFERENCE FOR GADTS Tom Schrijvers, Simon Peyton Jones, Martin Sulzmann and Dimitrios Vytiniotis CONTROL-FLOW ANALYSIS OF FUNCTION CALLS AND RETURNS BY ABSTRACT INTERPRETATION Jan Midtgaard and Thomas P. Jensen EDUCATIONAL PEARL: FUN FOR FRESHMEN KIDS Matthias Felleisen, Robert Bruce Findler, Matthew Flatt and Shriram Krishnamurthi EFFECTIVE INTERACTIVE PROOFS FOR HIGHER-ORDER IMPERATIVE PROGRAMS Adam Chlipala, Gregory Malecha, Greg Morrisett, Avraham Shinnar and Ryan Wisnesky EXPERIENCE REPORT: EMBEDDED, PARALLEL COMPUTER-VISION WITH A FUNCTIONAL DSL Ryan Newton and Teresa Ko EXPERIENCE REPORT: HASKELL IN THE REALWORLD Curt Sampson EXPERIENCE REPORT: OCAML FOR AN INDUSTRIAL-STRENGTH STATIC ANALYSIS FRAMEWORK Pascal Cuoq and Julien Signoles EXPERIENCE REPORT: OCSIGEN, A WEB PROGRAMMING FRAMEWORK Vincent Balat, Jérôme Vouillon and Boris Yakobowski EXPERIENCE REPORT: SEL4 -- FORMALLY VERIFYING A HIGH-PERFORMANCE MICROKERNEL Gerwin Klein, Philip Derrin and Kevin Elphinstone FINDING RACE CONDITIONS IN ERLANG WITH QUICKCHECK AND PULSE Koen Claessen, Michal Palka, Nicholas Smallbone, John Hughes, Hans Svensson, Thomas Arts and Ulf Wiger FREE THEOREMS INVOLVING TYPE CONSTRUCTOR CLASSES Janis Voigtlaender GENERIC PROGRAMMING WITH FIXED POINTS FOR MUTUALLY RECURSIVE DATATYPES Alexey Rodriguez, Stefan Holdermans, Andres Löh and Johan Jeuring IDENTIFYING QUERY INCOMPATIBILITIES WITH EVOLVING XML SCHEMAS Pierre Geneves, Nabil Layaida and Vincent Quint IMPLEMENTING FIRST-CLASS POLYMORPHIC DELIMITED CONTINUATIONS BY A TYPE-DIRECTED SELECTIVE CPS-TRANSFORM Tiark Rompf, Ingo Maier and Martin Odersky LA TOUR D'HANOï Ralf Hinze NON-PARAMETRIC PARAMETRICITY Georg Neis, Derek Dreyer and Andreas Rossberg OXENSTORED: AN EFFICIENT HIERARCHICAL AND TRANSACTIONAL DATABASE USING FUNCTIONAL PROGRAMMING WITH REFERENCE CELL COMPARISONS Thomas Gazagnaire and Vincent Hanquez PARALLEL CONCURRENT ML John Reppy, Claudio Russo and Yingqi Xiao PARTIAL MEMOIZATION OF CONCURRENCY AND COMMUNICATION Suresh Jagannathan, KC Sivaramakrishnan and Lukasz Ziarek PURELY FUNCTIONAL LAZY NON-DETERMINISTIC PROGRAMMING Sebastian Fischer, Oleg Kiselyov and Chung-chieh Shan RUNTIME SUPPORT FOR MULTICORE HASKELL Simon Marlow, Simon Peyton Jones and Satnam Singh SAFE FUNCTIONAL REACTIVE PROGRAMMING THROUGH DEPENDENT TYPES Neil Sculthorpe and Henrik Nilsson SCRIBBLE: CLOSING THE BOOK ON AD HOC DOCUMENTATION TOOLS Matthew Flatt, Eli Barzilay and Robert Bruce Findler USING OBJECTIVE CAML TO DEVELOP SAFETY-CRITICAL EMBEDDED TOOL IN A CERTIFICATION FRAMEWORK Bruno Pagano, Olivier Andrieu, Thomas Moniot, Benjamin Canou, Emmanuel Chailloux, Philippe Wang, Pascal Manoury and Jean-Louis Colaco

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#haskell.pt IRC channel
by Marco Túlio Gontijo e Silva 15 May '09

15 May '09

Hello, I'd like to invite all Portuguese speakers haskellers to join #haskell.pt in irc.freenode.net. I added it to the list in http://www.haskell.org/haskellwiki/IRC_channel . Greetings. -- marcot http://marcot.iaaeee.org/

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Pretty printing a tree
by José Romildo Malaquias 15 May '09

15 May '09

Hello. I would like to pretty print a tree in a way that its structure is easily perceived. For instance, consider the declarations: data Node a = Node a [Node a] type Tree a = [ Node a ] t = [ Node "a" [ Node "b" [] , Node "c" [ Node "c1" [] , Node "c2" [] ] , Node "d" [ Node "d1" [ Node "d1a" [] ] , Node "d2" [] ] ] ] Then the resulting of pretty printing the given tree would be something like the following: a | +-------------+ | | | b c d | | +---+ +---+ | | | | c1 c2 d1 d2 | d1a There is the module Text.PrettyPrint.HughesPJ, but it lacks examples on how to use the pretty print combinators, and it is not well docomented. I would like to see solutions for this problem, or clues on how to solve it. Regards, José Romildo

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looking for suggestion on pattern matching problem
by Daryoush Mehrtash 14 May '09

14 May '09

I am trying to analyze a list of items (say integers) for longest matches on patterns and their location on the list. One catch is that pattern may be defined in terms of other patterns. Example of patterns would be the any sequence of increasing numbers, or sequence of increasing numbers followed by upto 5 zeros then followed by any odd digits. I don't know much about the actual patterns, but would like to be able to define EDSL for composing the patterns and an execution environment to actually find the patterns. I like to find out various ways I can structure the problem and its trade offs. I appreciate any books, articles, suggestions, papers, etc on this type of problems. Thanks, Daryoush

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"hiddenness"
by Vasili I. Galchin 14 May '09

14 May '09

Hello, When I am compiling a module, I get "Could not find module 'Control.Module.State': it is a member of package mtl-1.1.0.2, which is hidden" 1) What is the efficacy of "hiddenness"? 2) I have forgotten what tool I run to expose a package. ?? 3) In another vein, the code is using Data.Finitemap ... so I guess I must "darcs" install this? Regards, Vasili

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Recommending "Design concepts in programming languages"
by Eugene Kirpichov 14 May '09

14 May '09

Hi. To all those people who are in any sense interested in PL theory I'd like to recommend the book "Design concepts in programming languages", because I am extremely impressed with it and because I, surprisingly, have not heard much about it. So, the book is about various concepts encountered in various kinds of programming languages: denotational and operational (BOS/SOS) semantics, issues of state and control, type systems, modules, modeling effects and compilation. Every concept is introduced by defining the semantics of a language that has this concept and exploring the design dimensions and issues of this concept and language. Concepts are gradually accumulated, and by the time you reach the chapter on modules you've got a CBV language with records, mutable state, polymorphic algebraic data types, a System F type system with type inference and a hint of dependent types, abstract data types and first-class dynamically loadable modules. The tools used for description are of course the good old denotational and operational semantics and typing judgements and derivation trees; but each element of those is clearly and succintly described in text; it happens to me all the time that I am reading a type reconstruction algorithm and wondering, "why does this rule have that restriction?" and it immediately turns out that in the next paragraph, the authors focus attention on why this rule has that restriction; just like if they were reading my thoughts. That's why this book feels very comfortable to me: I am absolutely sure that I won't encounter a point where I am lost and buried under the notation; but there is also not a single boring moment. I've been interested in functional programming and PL theory for 2-3 years already, and here's a brief list of the *new* things that I have learned, at least: - What do SOS and BOS mean, and why one should care, and what properties a SOS might posess (confluence and normalization, for instance) - How many features of languages can be defined in terms of simply desugaring, and how in some cases they can't - How one might use monadic style in the semantics metalanguage to greatly simplify the semantic rules for monadic concepts like state, control and error handling (the authors mention the word "monad" only once, but they use return- and bind-like operators in their semantics) - How powerful records are, and of what use are operators like "conceal" - What use is subtyping outside of OOP - How does one define CPS-style semantics and how such a style allows to add state, control and errors with minimal changes - How small yet powerful an OOP language core can be - How algebraic datatypes can be very useful in a language without static typing - How pattern matching can be desugared into CPS-style deconstructors - How many caveats are there in defining typing rules, and how a small change in them can lead to very big changes in language expressiveness - How HM type inference actually works - Why purity is important for certain polymorphism issues - What let-polymorphism means - What effect systems are - How effect reconstruction works and how it is different from type reconstruction in nature - How effect inference can prove the external purity of certain internally impure programs That's where I finished my reading for now. The remaining looks even more intriguing; for example, I don't (yet) know how functional languages are compiled and how register allocation is done. I'm afraid to sound like a salesman, but this is absolutely the best-written technical book I have ever seen in my life, and probably the most influential one for me, excluding probably SICP. Here you can check out its table of contents: http://cs.wellesley.edu/~fturbak/pubs/6821/current/contents-nov22.pdf I was impressed with the TOC even before buying the book, but turned out that I was greatly under-estimating it. Well, that's it :) -- Eugene Kirpichov Web IR developer, market.yandex.ru

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