March 2010 - Haskell - Haskell.org

GT-VMT 2010: cfp
by Emilio Tuosto 09 Mar '10

09 Mar '10

================================================================ Call for Participation 9th International Workshop on Graph Transformation and Visual Modeling Techniques (GT-VMT 2010) http://www.cs.le.ac.uk/events/gtvmt10/ Satellite Event of ETAPS 2010, Cyprus -- March 20-21, 2010 ============================================================== * Scope * GT-VMT 2010 is the ninth workshop of a series that serves as a forum for all researchers and practitioners interested in the use of graph-based notation, techniques, and tools for the specification, modeling, validation, manipulation and verification of complex systems. The aim of the workshop is to promote engineering approaches that provide effective sound tool support for visual modeling languages, enhancing formal reasoning at the semantic level (e.g., for model analysis, transformation, and consistency management) in different domains, such as UML, Petri nets, Graph Transformation or Business Process/Workflow Models. * Workshop Program SATURDAY 20 MARCH 2010 9:00-9:15 Opening 9:15-10:30 Invited talk: Fernando Orejas: Symbolic Attributed Graphs and Attributed Graph Transformation 10:30-11:00 Break 11:00-12:30 Session on Foundations Maarten de Mol and Arend Rensink. A Graph Representation for Ordered Edges. Davide Grohmann and Marino Miculan. Graph Algebras for Bigraphs. Christoph Blume, Sander Bruggink, and Barbara K�nig. Recognizable Graph Languages for Checking Invariants. 12:30-14:00 Lunch 14:00-15:30 Session on Modeling and Modeling Environments Frank Hermann, Andrea Corradini, Hartmut Ehrig, and Barbara K�nig. Efficient Process Analysis of Transformation Systems Based on Petri nets. Berthold Hoffmann and Mark Minas. Defining Models - Meta Models versus Graph Gammars. Torsten Strobl and Mark Minas. Specifying and generating editing environments for interactive animated visual models. 15:30-16:00 Break 16:00-17:00 Session on Interactions Vojtech Rehak, Petr Slovak, Jan Strejcek, and Loic Helouet. Decidable Race Condition and Open Coregions in HMSC. Abubakar Hassan, Ian Mackie, and Shinya Sato. A light-weight abstract machine for interaction nets. 17:00-17:30 Discussion SUNDAY 21 MARCH 2010 9:30-11:00 Session on Model Transformation Eugene Syriani and Hans Vangheluwe. De-/Re-constructing Model Transformation Languages. Bernhard Schaetz. Verification of Model Transformations. Paolo Bottoni, Andrew Fish, and Francesco Parisi-Presicce. Preserving constraints in horizontal model transformations. 11:00-11:30 Break 11:30-12:30 Session on Foundations Paolo Torrini, Reiko Heckel, Istvan Rath, and Gabor Bergmann. Stochastic Graph Transformation with Regions. Wolfram Kahl. Cotabulations, Bicolimits and Van-Kampen Squares in Collagories. 12:30-14:00 Lunch * Workshop organizers Jochen Kuester, IBM Research, Switzerland Emilio Tuosto, University of Leicester, UK * Program Committee Paolo Baldan (University of Padova, Italy) Artur Boronat (University of Leicester, UK) Andrea Corradini (University of Pisa, Italy) Claudia Ermel (TU Berlin, Germany) Gregor Engels (University of Paderborn, Germany) Reiko Heckel (University of Leicester, UK) Thomas Hildebrandt (ITU, Denmark) Holger Giese (HPI Potsdam, Germany) Barbara K�nig (University of Duisburg-Essen, Germany) Jochen K�ster (IBM Research - Zurich, Germany) Alberto Lluch Lafuente (IMT Institute for Advanced Studies Lucca, Italy) Juan de Lara (Universidad Aut�noma de Madrid, Spain) Mark Minas (Universit�t der Bundeswehr M�nchen, Germany) Francesco Parisi-Presicce (University of Rome, Italy) Arend Rensink (University of Twente, Netherlands) Gabriele Taentzer (University of Marburg, Germany) Emilio Tuosto (University of Leicester, UK) D�niel Varr� (TU Budapest, Hungary) Erhard Weinell (RWTH Aachen University, Germany) Albert Z�ndorf (University of Kassel, Germany) * More information on the workshop is available through the webpage: http://www.cs.le.ac.uk/events/gtvmt10/ -- *************************************************************** Emilio Tuosto Department of Computer Science University of Leicester Leicester, LE1 7RH United Kingdom Tel. +44 (0) 116 252 5392 Fax. +44 (0) 116 252 3915 homepage -> http://www.cs.le.ac.uk/people/et52 ***************************************************************

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ANN: hsndfile 0.4
by stefan kersten 09 Mar '10

09 Mar '10

i'm pleased to announce version 0.4 of hsndfile [1], a haskell interface to libsndfile [2]. in version 0.4 the buffer i/o interface has been simplified and instances for i/o based on the vector package [3] is provided by hsndfile-vector [4]. enjoy! <sk> [1] http://haskell.org/haskellwiki/Hsndfile [2] http://www.mega-nerd.com/libsndfile/ [3] http://hackage.haskell.org/package/vector [4] http://hackage.haskell.org/package/hsndfile-vector

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generalized newtype deriving breaks type class invariants. that is bad.
by John Meacham 09 Mar '10

09 Mar '10

On Mon, Mar 08, 2010 at 11:32:16PM +0100, Wolfgang Jeltsch wrote: > Generalized newtype deriving doesn’t just allow otherwise undefinable functions > to be defined. It probably also allows for faster function implementations. For > example, with the above conv method, you could probably convert a list of some > type [t] into a list of type [Wrapped t] in O(1) time. If you would code this > conversion by hand, it would take O(n) time, of course. So you can! wrapList :: [a] -> [Wrapped a] wrapList xs = conv xs > wrapList "Hello" [Wrap 'H',Wrap 'e',Wrap 'l',Wrap 'l',Wrap 'o'] This is quite interesting. And perhaps very, very bad. Take this example: > newtype Down a = Down a deriving (Iso a, Show, Eq) > > instance Ord a => Ord (Down a) where > compare (Down x) (Down y) = compare y x > downSet :: Set.Set a -> Set.Set (Down a) > downSet ss = conv ss > xs = "abcdef" > sxs1 = downSet (Set.fromList xs) > sxs2 = Set.fromList (map Down xs) Set.toAscList sxs1 [Down 'a',Down 'b',Down 'c',Down 'd',Down 'e',Down 'f'] Set.toAscList sxs2 [Down 'f',Down 'e',Down 'd',Down 'c',Down 'b',Down 'a'] We have been able to break the invarients of 'Set' using newtype deriving of a completely unrelated class 'Iso'. It seems that generalized newtype deriving may break type classes in a big way. John -- John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/

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Haskell Weekly News: Issue 152 - March 08, 2010
by jfredett＠gmail.com 08 Mar '10

08 Mar '10

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20100308 Issue 152 - March 08, 2010 --------------------------------------------------------------------------- Welcome to issue 152 of HWN, a newsletter covering developments in the [1]Haskell community. Hello Haskellers, this week brings updates to some standards (like Parsec), as well as some new tunes to the Haskell songbook. WAI and Yesod were released, giving some new options for Haskell-based web applications, Don Stewart made some improvements to his Genetic Optimizer system to include options from GHC's new LLVM backend, and I made some serious progress on the new HWN software. Speaking of the new software, there have been numerous reports of warts and other unfortunate things with the current editions of the HWN. Fear not, these warts are well known and being worked on intently. Unfortunately, it's somewhat difficult to fix them given the current publication software, however, in the new-and-improved version that (hopefully) should be entering use soon, these warts will be removed. So, without further interuption about the stylistic content, Haskellers, your Haskell Weekly News! Announcements Bluetile 0.3.1. Jan Vornberger [2]announced Bluetile, an adaptation of xmonad for the masses. Bluetile aims to make tiling window managers accessible by drawing on standard window manager conventions and idioms. ED: This is not technically an announcement, but it's very cool and everyone should check it out! yesod 0.0.0 (web framework). Michael Snoyman [3]announced the release of yesod, a web framework based on WAI. wai-0.0.0 (Web Application Interface). Michael Snoyman [4]announced the first release of wai, a library implementing the WAI protocol. iteratee-parsec 0.0.2. Maciej Piechotka [5]announced iteratee-parsec, a library which allows for parsec parsers in the IterateeG monad. Parsec 3.1.0. Derek Elkins [6]announced a new release of Parsec, containing many improvments due (primarily) to Antoine Latter. Progression-0.3 (supporting benchmarking in Haskell). Neil Brown [7]announced a new release of Progression. Progression is a utility built on top of Criterion for recording benchmarks for several version of your code. Ghent Functional Programming Group: First Meeting on April 1, 2010. Jeroen Janssen [8]announced the first meeting of the Ghent Functional Programming group, see the post for location and time details. PhD position in Functional Programming at Chalmers (deadline 2010-04-07). Patrik Jansson [9]announced an opening for a PhD student at Chalmers, working in Functional Programming and DSELs. VSTTE 2010: Verified Software -- Third Call for Papers. Gudmund Grov [10]announced a third CFP for VSTTE 2010, the Third International Conference on Verified Software: Theories, Tools, and Experiments. barchart-0.1.1. Sebastian Fischer [11]announced barchart, a command line program with an associated library for generating bar charts. Call for Participation: CHR Summer School. Jon Sneyers [12]announced a call for participation in the CHR Summer School on Programming and Reasoning with Rules and Constraints. Discussion Free theorem - what do we need it for. Maciej Piechotka [13]asked about Free Theorems and what they were good for. Has anybody translated Douglas Hofstadter's Scientific American articles introducting Scheme to a general audience into Haskell? Benjamin L. Russell [14]asked if anyone had considered translating Douglas Hofstadter's SciAm articles introducting Scheme to Haskell. Evolving Faster Haskell Programs (now with LLVM!). Don Stewart [15]our resident speed demon is at it again, harnessing the new LLVM backend of GHC and the power of Natural Selection to make his programs go even faster. Blog noise [16]Haskell news from the [17]blogosphere. Blog posts from people new to the Haskell community are marked with >>>, be sure to welcome them! * Neil Brown: [18]Synchronous Channels using MVars. * "FP Lunch": [19]Causal Semantics of (A)FRP. * Darcs: [20]darcs weekly news #56. * Dan Piponi (sigfpe): [21]Products, Limits and Parametric Polymorphism. * Bryn Keller: [22]Real World Haskell. * Isaac Dupree: [23]Next Project, Move doc-parsing to from GHC to Haddock. * Isaac Dupree: [24]Summer of Code Wrap-Up.. * Isaac Dupree: [25]Status update. * Isaac Dupree: [26]platform progress. * Isaac Dupree: [27]another boring update, & question :-). * Isaac Dupree: [28]How To Navigate Your Code:. * Michael Snoyman: [29]Persistence. * Neil Brown: [30]Choice over Events using STM. * Michael Snoyman: [31]Tweedle Beetle Battle. * Galois, Inc: [32]The Semantics of Asynchronous Exceptions. * Bryan O'Sullivan: [33]What's in a parser? Attoparsec rewired (2/2). * Bryan O'Sullivan: [34]What's in a parsing library? (1/2). * Neil Brown: [35]Progression 0.3: Bar Charts and Normalisation. Quotes of the Week * edwardk: heh, i'm amused the ParsecT that Antoine Latter put together is in the form of a right kan extension ;) * Philippa: <TR1N1TY> I'm selling botz and backdoors <Philippa> I'm selling bans * samlee (via reddit): haha those ghc options are longer than actual program About the Haskell Weekly News New editions are posted to [36]the Haskell mailing list as well as to [37]the Haskell Sequence and [38]Planet Haskell. [39]RSS is also available, and headlines appear on [40]haskell.org. To help create new editions of this newsletter, please see the information on [41]how to contribute. Send stories to jfredett . at . gmail . dot . com. The darcs repository is available at darcs get [42]http://patch-tag.com/r/jfredett/HWN2/pullrepo HWN2 . References 1. http://haskell.org/ 2. http://www.bluetile.org/ 3. http://article.gmane.org/gmane.comp.lang.haskell.cafe/71314 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/71184 5. http://article.gmane.org/gmane.comp.lang.haskell.cafe/71144 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/71122 7. http://article.gmane.org/gmane.comp.lang.haskell.cafe/71041 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/70981 9. http://article.gmane.org/gmane.comp.lang.haskell.general/17842 10. http://article.gmane.org/gmane.comp.lang.haskell.general/17841 11. http://article.gmane.org/gmane.comp.lang.haskell.general/17831 12. http://article.gmane.org/gmane.comp.lang.haskell.general/17825 13. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/71117 14. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/71022 15. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/70967 16. http://planet.haskell.org/ 17. http://haskell.org/haskellwiki/Blog_articles 18. http://chplib.wordpress.com/2010/03/08/synchronous-channels-using-mvars/ 19. http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=369 20. http://blog.darcs.net/2010/03/darcs-weekly-news-56.html 21. http://blog.sigfpe.com/2010/03/products-limits-and-parametric.html 22. http://www.xoltar.org/?p=36 23. http://haddock2009.wordpress.com/2009/07/21/next-project-move-doc-parsing-t… 24. http://haddock2009.wordpress.com/2009/08/26/summer-of-code-wrap-up/ 25. http://haddock2009.wordpress.com/2009/05/12/status-update/ 26. http://haddock2009.wordpress.com/2009/05/20/platform-progress/ 27. http://haddock2009.wordpress.com/2009/05/26/another-boring-update-question/ 28. http://haddock2009.wordpress.com/2009/06/23/how-to-navigate-your-code/ 29. http://www.snoyman.com/blog/entry/persistence/ 30. http://chplib.wordpress.com/2010/03/04/choice-over-events-using-stm/ 31. http://www.snoyman.com/blog/entry/tweedle-beetle-battle/ 32. http://www.galois.com/blog/2010/03/04/the-semantics-of-asynchronous-excepti… 33. http://www.serpentine.com/blog/2010/03/03/whats-in-a-parser-attoparsec-rewi… 34. http://www.serpentine.com/blog/2010/03/03/whats-in-a-parsing-library-1/ 35. http://chplib.wordpress.com/2010/03/02/progression-0-3-bar-charts-and-norma… 36. http://www.haskell.org/mailman/listinfo/haskell 37. http://sequence.complete.org/ 38. http://planet.haskell.org/ 39. http://sequence.complete.org/node/feed 40. http://haskell.org/ 41. http://haskell.org/haskellwiki/HWN 42. http://patch-tag.com/r/jfredett/HWN2/pullrepo%20HWN2

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PhD position in Functional Programming at Chalmers (deadline 2010-04-07)
by Patrik Jansson 08 Mar '10

08 Mar '10

Come and work with us! The Chalmers FP group is recruiting a PhD student to work on FP and DSELs. Details are here http://www.chalmers.se/cse/EN/news/vacancies/positions/phd-student-position… and below. Welcome! Patrik Jansson, Koen Claessen, Mary Sheeran, John Hughes ---- Job description The PhD student will join the research activities at our department in the area of functional programming, much of which concentrates on the design and application of Domain Specific Embedded Languages (DSELs). Examples of our previous work in this area are Lava, a language for hardware description and verification, QuickCheck, a DSL for specifying and testing programs and PolyP, a language for generic functional programming. Our goals for the coming four years are to develop theories and tools that make future DSELs easier to design, implement, and use. Concretely, we aim for making reusable, generic libraries that capture common aspects occurring in many DSELs, such as symbolic simulation and error messages. Moreover, we want to develop domain-specific specification, testing and verification methods, using for example QuickCheck and automated theorem proving techniques, that exploit the particular restrictions that programs in the DSL at hand obey. All this will be done in the context of the concrete DSELs the group is already working on. http://www.chalmers.se/cse/EN/news/vacancies/positions/phd-student-position…

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VSTTE 2010: Verified Software -- Third Call for Papers
by Gudmund Grov 08 Mar '10

08 Mar '10

(Apologies if you receive multiple copies of this announcement) ***************************************************************** Third International Conference on Verified Software: Theories, Tools, and Experiments Call for Conference & Workshop Papers Edinburgh, Scotland August 16th-19th, 2010 http://www.macs.hw.ac.uk/vstte10 SPONSORS National Science Foundation (NSF) Engineering and Physical Sciences Research Council (EPSRC) Microsoft Research Scottish Informatics & Computer Science Alliance (SICSA) Altran Praxis Software Systems Engineering Initiative (SSEI) Formal Methods Europe (FME) To become a sponsor see: http://www.macs.hw.ac.uk/vstte10/Sponsors.html ****************************************************************** The Third International Conference on Verified Software: Theories, Tools, and Experiments follows a successful inaugural working conference at Zurich (2005) and a successful conference in Toronto (2008). This conference is part of the Verified Software Initiative (VSI), a fifteen-year, cooperative, international project directed at the scientific challenges of large-scale software verification. VSI also includes UKCRC's Grand Challenge 6, i.e. Dependable Systems Evolution. VSTTE is open to anyone who is interested in participating actively in the VSI effort. SCOPE The goal of this conference is to advance the state of the art in the science and technology of software verification through the interaction of theory development, tool evolution, and experimental validation. Authors are encouraged to submit work in progress, particularly if the work involves collaboration, theory unification, and tool integration. Topics of interest include requirements modeling specification languages specification/verification case-studies formal calculi programming languages language semantics software design methods software testing automatic code generation refinement methodologies type systems computer security verification tools (static analysis, dynamic analysis, model checking, theorem proving, satisfiability) tool integration benchmarks challenge problems integrated verification environments We also encourage researchers to submit challenges in theory, formalization, systems verification, code verification, and applications. Contributions relating to existing challenges will also be welcomed, i.e. * POPLMark (http://tinyurl.com/poplmark) * Tokeneer (http://www.adacore.com/home/products/sparkpro/tokeneer) * POSIX file system (http://tinyurl.com/qyzqk9) * medical devices (http://tinyurl.com/pnztqb) VENUE VSTTE 2010 is being hosted by Heriot-Watt University in Edinburgh. The conference dates coincide with the 2010 Edinburgh International Festival and the Edinburgh Festival Fringe -- collectively the largest annual arts festival on the planet! The technical programme will take place in the Edinburgh Conference Centre (Riccarton campus), where accommodation will be available at very competitive rates for festival time. Social events will be arranged within the city centre, making VSTTE an unique cultural and scholarly event for 2010! INVITED SPEAKERS * Tom Ball (Microsoft Research, Redmond) * Gerwin Klein (National ICT Australia) * Matthew Parkinson (University of Cambridge) SUBMISSIONS Submitted research papers and system descriptions must be original and not submitted for publication elsewhere. Research paper submissions are limited to 15 proceedings pages in LNCS format and must include a cogent and self-contained description of the ideas, methods and results, together with a comparison to existing work. System descriptions are also limited to 15 proceedings pages in LNCS format. Submissions of theoretical, practical, and experimental contributions are equally encouraged, including those that focus on specific problems or problem domains. Papers can be submitted at https://www.easychair.org/login.cgi?conf=vstte10. Submissions that arrive late, are not in the proper format, or are too long will not be considered. The proceedings of VSTTE 2010 will be published by Springer-Verlag in the LNCS series. Authors of accepted papers will be requested to sign a form transferring copyright of their contribution to Springer-Verlag. The use of LaTeX and the Springer llncs class files, obtainable from http://www.springer.de/comp/lncs/authors.html, is strongly encouraged. WORKSHOPS In addition to the main conference, VSTTE will host two workshops on August 19th: * VS-Theory focuses on theoretical foundations of software verification. Topics range from the difficult and essential study of soundness of delicate proof methods, to the discovery of new specification techniques and proof methods, to dramatic simplification or unification of existing methods, to as yet unknown breakthroughs. * VS-Tools & Experiments focuses on the development of verification tools and their experimental evaluation. Possible topics include interfaces between tools, tool integration platforms, and case studies. The workshops will provide a forum to present new, possibly unfinished work and will also give the opportunity to propose research challenges, which will help form a research agenda for the Verified Software Initiative. Papers must be written in English using Springer LNCS style. The page limit is 10 pages for technical papers and 5 pages for proposals of verification challenges. The proceedings will be published as a technical report. IMPORTANT DATES March 29 2010: Conference paper submission deadline May 10 2010: Decisions on papers May 21 2010: Workshop paper submission June 1 2010 Final conference paper versions due June 23 2010: Final workshop paper version August 16-18 2010: Main conference August 19 2010: Workshops RESEARCH STUDENT SUPPORT A limited number of grants, cover registration and travel, will be available to support PhD students wishing to attend VSTTE 2010. More details to follow via the website. SUMMER SCHOOL There will be a two-day summer-school preceding the main conference on the 14 and 15 August. The summer school will give a broad overview of software verification techniques, addressing both bottom-up and top-down approaches with a strong focus on the formal representation and reasoning themes. The school consists of eight introductory lectures, each concentrating on an unique aspect of one or both of the overall themes. The topics of the lectures include inductive theorem proving; SAT and SMT solving; proof planning and rippling; rely/guarantee conditions; separation logic; operating system verification; BiGraphs and formal analysis of security. The following will present at the summer school: * Robert Atkey (University of Strathclyde) & Ewen Maclean (Heriot-Watt University) * Alan Bundy & Lucas Dixon (University of Edinburgh) * Cliff Jones (University of Newcastle) * Gerwin Klein (National ICT Australia) * Robin Milner (University of Cambridge/Edinburgh) * J Strother Moore (University of Texas at Austin) * Natarajan Shankar (SRI) * Graham Steel (INRIA) The school is intended for PhD students and researchers working within one or both of these themes, however familiarity with any of the techniques is not a prerequisite. All lectures are meant to be introductory. For more information see: http://dream.inf.ed.ac.uk/events/ssfrr-2010/ COMPETITION A verification competition will be held at VSTTE 2010. The challenge is to develop a machine-verified piece of software with respect to a given specification. The competition will be conducted over a 2.5 hour period on some evening of the conference. The problem will be presented with a logical specification and test cases over .5 hours including time for discussion with 2 hours to construct a solution. Each competing team can feature up to three members. You can use any tool or combination of tools as well as libraries, but you cannot modify these tools. You can reinterpret the specification to suit your tools and methods, but you will be judged on the fidelity of your interpretation. The goal is to produce an executable program and a replayable proof that the program meets the specification. It will be possible to code the solution using integers and arrays. The solutions will be judged for soundness (absence of bugs) and completeness (presence of proofs). The three best solutions will be selected and the respective teams will be invited to make presentations at the tools/experiments workshop. You must register a copy of the verification system with the judges prior to the competition with instructions for replaying proofs and running the programs. CONFERENCE CHAIR Andrew Ireland (Heriot-Watt University; A.Ireland(a)hw.ac.uk) PROGRAM CHAIRS Peter O'Hearn (Queen Mary, University of London; ohearn(a)dcs.qmul.ac.uk) Gary T. Leavens (University of Central Florida; leavens(a)eecs.ucf.edu) Sriram Rajamani (Microsoft Research; sriram(a)microsoft.com) WORKSHOP GENERAL CHAIR Peter Mueller (ETH Zurich; peter.mueller(a)inf.ethz.ch) THEORY WORKSHOP CHAIRS David Naumann (Stevens Institute of Technology; dnaumann(a)stevens.edu) Hongseok Yang (Queen Mary, University of London; hyang(a)dcs.qmul.ac.uk) TOOLS & EXPERIMENTS WORKSHOP CHAIRS Rajeev Joshi (NASA JPL; rajeev.joshi(a)jpl.nasa.gov) Tiziana Margaria (Universit√§t Potsdam; margaria(a)cs.uni-potsdam.de) PUBLICITY CHAIR Gudmund Grov (Edinburgh University; ggrov(a)inf.ed.ac.uk) LOCAL ARRANGEMENT CHAIR Ewen Maclean (Heriot-Watt University; E.A.H.Maclean(a)hw.ac.uk) CONFERENCE PROGRAM COMMITTEE Ahmed Bouajjani Leo Freitas Philippa Gardner John Hatcliff Ranjit Jhala Joseph Kiniry Rustan Leino Xavier Leroy David Naumann Matthew Parkinson Wolfgang Paul Shaz Qadeer Andrey Rybalchenko Augusto Sampaio Zhong Shao Aaron Stump Serdar Tasiran Willem Visser Chin Wei-Ngan Stephanie Weirich Greta Yorsh STEERING COMMITTEE Tony Hoare Jay Misra Natarajan Shankar Jim Woodcock -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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ANNOUNCE: barchart-0.1.1
by Sebastian Fischer 08 Mar '10

08 Mar '10

barchart is a command-line program with associated Haskell library for generating bar charts, for example, from CSV files. It has special support for creating charts from data generated by the Haskell benchmarking tools criterion and progression. Instead of drawing bars of different benchmarks next to each other like progression does, barchart draws one bar for each benchmarked implementation where the benchmarks are represented as blocks of the same bar. As a consequence, one can recognise on first sight, which implementation is the fastest _in total_ because the hight of each bar is the sum of run times of all benchmarks for an implementation. Another difference to progression is that barchart is (only) a post processor and you usually do not import barchart modules into your Haskell code. Please refer to the project website for more information: http://sebfisch.github.com/haskell-barchart/ I would not have written this program without the Diagrams library by Brent Yorgey and the CmdArgs package by Neil Mitchell. Thank you for your excellent libraries! I hope barchart is useful for some of you! Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)

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Some help in operator precedence
by Edgar Z. Alvarenga 08 Mar '10

08 Mar '10

I created a simple program in Haskell to simulate the Physics Ising model (http://en.wikipedia.org/wiki/Ising_model) with Metropolis algorithm: http://haskell.pastebin.com/Zt0gguEa And used Data.Vector.Unboxed.Mutable to model de 2D grid. To this a used a unidimensional vector, but created a operator to write and other to read the vector using a tuple to specify the position: newtype Grid = Grid { unG :: (Int, MVector (PrimState IO) Int) } newtype Ising = Ising { unI :: (M.MTGen, Grid) } type Pos = (Int, Int) (|>) :: Grid -> Pos -> IO Int (Grid (n,g)) |> (x,y) | x == n = U.unsafeRead g (y*n) | x == -1 = U.unsafeRead g (y*n + n - 1) | y == n = U.unsafeRead g x | y == -1 = U.unsafeRead g ((n - 1)*n + x) | otherwise = U.unsafeRead g (y*n + x) (<==) :: Pos -> Int -> (Pos, Int) pos <== val = (pos,val) (<|) :: Grid -> (Pos, Int) -> IO () Grid (n,g) <| ((x,y), val) = U.unsafeWrite g (y*n + x) val infixr 1 <== infixr 0 <| With this I can write expressions like: s <- g |> (x,y) grid <| (i,j) <== spin (rnumber `mod` 2) my problem is with the (<==) and (<|) operators, because in the way I defined I can't use: grid <| (i,j) <== spin $ rnumber `mod` 2 Is there way to solve this and don't have to use the parenthesis on the right expression? And I really would like to now with this approach to the 2D vector is a good idea or is better to use another data structur instead of the mutable vector. Comments about the code are really welcome. Edgar

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Re: [Haskell] Recursive definition of fibonacci with Data.Vector
by Edgar Z. Alvarenga 07 Mar '10

07 Mar '10

On Sun, 07/Mar/2010 at 17:04 -0500, Brian Sniffen wrote: > To what do you expect 'v' to refer? Data.Vector > Why use 'let' for the definition? > > And then once you sort it out to something like: > > fib = 0 `V.cons` (1 `V.cons` V.zipWith (+) fib (V.tail fib)) Was just a typo (the line above was copy from ghci). > The three Vector operations used here are strict in the length of > their arguments. So what length should 'fib' have? 2 more than its > own length... which is more RAM than this computer has. Ok, now I understood, is because of the strictness. The next time I would look in the source code first. Thanks, Edgar > -Brian > > On Sun, Mar 7, 2010 at 3:49 PM, Edgar Z. Alvarenga <edgar(a)ymonad.com> wrote: > > Hello, > > > > why I can't define a recursive vector using Data.Vector, like in > > the example: > > > > import qualified Data.Vector as V > > > > let fib = 0 `V.cons` (1 `V.cons` V.zipWith (+) fib (V.tail v)) > > > > Cheers, > > Edgar > > _______________________________________________ > > Haskell mailing list > > Haskell(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell > > > > > > -- > Brian Sniffen > http://evenmere.org/~bts/ > <bts(a)evenmere.org>

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Recursive definition of fibonacci with Data.Vector
by Edgar Z. Alvarenga 07 Mar '10

07 Mar '10

Hello, why I can't define a recursive vector using Data.Vector, like in the example: import qualified Data.Vector as V let fib = 0 `V.cons` (1 `V.cons` V.zipWith (+) fib (V.tail v)) Cheers, Edgar

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