September 2008 - Haskell

ANNOUNCE: Extensible and Modular Generics for the Masses (EMGM) 0.1
by Sean Leather 20 Sep '08

20 Sep '08

Extensible and Modular Generics for the Masses ============================================== Extensible and Modular Generics for the Masses (EMGM) is a library for generic programming in Haskell using type classes. This is the initial release of a maintained library for EMGM. Other versions have previously existed in various states from various sources. We plan to continue updating and maintaining this version. Visit the home page: http://www.cs.uu.nl/wiki/GenericProgramming/EMGM Features -------- The primary features of EMGM include: * Datatype-generic programming using sum-of-product views * Large collection of ready-to-use generic functions * Included support for standard datatypes: lists, Maybe, tuples * Easy to add support for new datatypes * Type classes make writing new functions straightforward in a structurally inductive style * Generic functions are extensible with ad-hoc cases for arbitrary datatypes * Good performance of generic functions The features of this distribution include: * The API is thoroughly documented with Haddock * Fully tested with QuickCheck and HUnit * Program coverage ensures that all useful code has been touched by tests * Tested on both Mac and Windows systems Requirements ------------ EMGM has the following requirements: * GHC 6.8.1 - It has been tested with versions 6.8.3 and 6.9.20080916. * Cabal library 1.2.1 - It has been tested with versions 1.2.3 and 1.4.0.1. Download & Source ----------------- Use caball-install: cabal install emgm Get the package: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm Get the source: svn checkout https://svn.cs.uu.nl:12443/repos/dgp-haskell/EMGM Examples -------- Check out the examples: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/examples/ Bugs & Support -------------- Report issues or request features: http://code.google.com/p/emgm/ Discuss EMGM with the authors, maintainers, and other interested persons: http://www.haskell.org/mailman/listinfo/generics Credits ------- The research for EMGM originated with Ralf Hinze. It was extended with work by Bruno Oliveira and Andres Löh. More details of the library functionality were explored by Alexey Rodriguez. We are very grateful to all of these people for the foundation on which this library was built. The current authors and maintainers of EMGM are: * Sean Leather * José Pedro Magalhães * Alexey Rodriguez * Andres Löh

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DAMP 2009: Call for Papers
by Manuel M T Chakravarty 18 Sep '08

18 Sep '08

C a l l f o r P a p e r s DAMP 2009: Workshop on Declarative Aspects of Multicore Programming Savannah, Georgia, USA --- January 20, 2009 (co-located with POPL 2009) DAMP 2009 is the fourth in a series of one-day workshops seeking to explore ideas in programming language design that will greatly simplify programming for multicore architectures, and more generally for tightly coupled parallel architectures. DAMP 2009 is co-located with the ACM SIGPLAN - SIGACT Symposium on Principles of Programming Languages (POPL 2009). The emphasis will be on functional and (constraint-)logic programming, but any programming language ideas that aim to raise the level of abstraction are welcome. DAMP seeks to gather together researchers in declarative approaches to parallel programming and to foster cross fertilization across different approaches. For further information, a CFP flyer, and details on paper submissions, see http://www.cse.unsw.edu.au/~pls/damp09/ Paper submission deadline is 10th October 2008!

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Re: Haskell Weekly News: Issue 85 - September 13, 2008
by Benjamin L.Russell 18 Sep '08

18 Sep '08

On Sat, 13 Sep 2008 21:06:21 -0700, "Daryoush Mehrtash" <dmehrtash(a)gmail.com> wrote: >I have a newbie question.... Does theorem proofs have a use for an >application? Take for example the IRC bot example ( >http://www.haskell.org/haskellwiki/Roll_your_own_IRC_bot) listed below. Is >there any insight to be gained by theorem proofs (as in COQ) into the app? Yes. Basically, if you can prove that the program is correct, then you don't need to test it. While proofs can become very tedious for huge programs with many different kinds of control flow involving very complicated logic, if the program size can be shortened to a reasonable size, then proofs can help shorten development time. This was actually part of the motivation for developing Haskell as a pure functional programming language (i.e., one that prohibits side effects -- see http://www.haskell.org/haskellwiki/Functional_programming) It is generally easier to write proofs for pure functional programming languages than for impure ones. Theorem provers help to automate the process of writing proofs for programs. Djinn (see http://lambda-the-ultimate.org/node/1178) is an example of a theorem prover for Haskell. Given a (Haskell function), it returns a function of that type if one exists. Here is a sample Djinn session (courtesy of http://lambda-the-ultimate.org/node/1178) > calvin% djinn > Welcome to Djinn version 2005-12-11. > Type :h to get help. ># Djinn is interactive if not given any arguments. ># Let's see if it can find the identity function. > Djinn> f ? a->a > f :: a -> a > f x1 = x1 ># Yes, that was easy. Let's try some tuple munging. > Djinn> sel ? ((a,b),(c,d)) -> (b,c) > sel :: ((a, b), (c, d)) -> (b, c) > sel ((_, v5), (v6, _)) = (v5, v6) > ># We can ask for the impossible, but then we get what we ># deserve. > Djinn> cast ? a->b > -- cast cannot be realized. > ># OK, let's be bold and try some functions that are tricky to write: ># return, bind, and callCC in the continuation monad > Djinn> type C a = (a -> r) -> r > Djinn> returnC ? a -> C a > returnC :: a -> C a > returnC x1 x2 = x2 x1 > > Djinn> bindC ? C a -> (a -> C b) -> C b > bindC :: C a -> (a -> C b) -> C b > bindC x1 x2 x3 = x1 (\ c15 -> x2 c15 (\ c17 -> x3 c17)) > > Djinn> callCC ? ((a -> C b) -> C a) -> C a > callCC :: ((a -> C b) -> C a) -> C a > callCC x1 x2 = x1 (\ c15 _ -> x2 c15) (\ c11 -> x2 c11) ># Well, poor Djinn has a sweaty brow after deducing the code ># for callCC so we had better quit. > Djinn> :q > Bye. Other theorem provers include COQ (see http://coq.inria.fr/) and Sparkle (see http://www.cs.ru.nl/Sparkle/) (a theorem prover for the alternative non-strict, purely function programming language Clean (see http://clean.cs.ru.nl/)) -- Benjamin L. Russell

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ANNOUNCE: qtHaskell 1.1.2, the second preview version of qtHaskell
by David Harley 16 Sep '08

16 Sep '08

For all interested in Haskell GUIs, there is now a second preview release of qtHaskell - a set of Haskell bindings for Trolltech's Qt available at http://qthaskell.berlios.de There are a number of important changes from the previous version. 1. All FFI pointers are now Foreign Pointers. Those of a type derived from QObject are wrapped as QPointer types and only this wrapper is deleted when their finalizer runs. All other types are automatically deleted by their finalizer when they go out of Haskell scope - or more precisely when the finalizer acutally runs. To make the actual deletion time more easily controlable, most example code uses the function "returnGC" instead of just "return" in callback functions. Also non QObject derived types can be constructed with an alternative constructor qSomeObject_nf which has no finalizer. In this case it's the programmers job to delete the object when required. 2. All Qt enumerated types are implemented as equivalent Haskell types instead of just being of type Int as before. In fact I'v used separate types for enumerated types and their corresponding "flags" types in Qt. For example enum Qt::AlignmentFlag flags Qt::Alignment have equivalent qHaskell types: data CQt__AlignmentFlag a = CQt__AlignmentFlag a type Qt__AlignmentFlag = QEnum(CQt__AlignmentFlag Int) data CQt__Alignment a = CQt__Alignment a type Qt__Alignment = QFlags(CQt__Alignment Int) and a corresponding set of value functions i.e. qt__AlignLeft and qtf__AlignLeft qt__AlignRight and qtf__AlignRight ... The correct value function must be used depending on the parameter type of the api function being called e.g. buttonBox <- qDialogButtonBox1 (qDialogButtonBoxf__Ok + qDialogButtonBoxf__Cancel) for a "flags" type in "widgets.hs", or slider <- qSlider1 qt__Vertical for an "enum" type in "hellogl.hs" 3. All qtHaskell functions which correspond to some overloaded Qt api function use a final numeral in their name which corresponds to the number of parameters in the function. For example: QRect () QRect ( const QPoint & topLeft, const QPoint & bottomRight ) QRect ( const QPoint & topLeft, const QSize & size ) QRect ( int x, int y, int width, int height ) becomes qRect qRect2 qRect4 where qRect2 is a class of functions that can take either QPoint or QSize for their second parameter. This nomeclature has the advantage of being compatible beteen different Qt versions and of making it possible for the qtHaskell programmer to tell what the name of the corresponding qtHaskell function is just by looking at the Qt documentation. N.B. although qtHaskell 1.1.1 programs are not therefore forwards compatible with qtHaskell 1.1.2, only minimal editing is required to upgrade them. 4. The Haskell api code is now split into separate modules for each Qt class. All these modules are exposed in the qtc package, hence by explicitly importing only the required modules for an application, the size of the corresponding executable can be kept to a reasonable size. All example qtHaskell programs have a corresponding program prefixed with "cs", which has only this explicit importing, e.g. "widgets" and "cswidgets". Some example programs have also a corresponding "as" prefixed program which uses explicit module importing and also uses Arthur Widgets, about which see below. 5. There are two new detailed examples, csterrainsim and csPathDeform. csterrainim, is an eventloop based realtime terrain simulator based on OpenGL and has a frame rate almost the same as its C++ original. csPathDeform, is a vector graphic demo program based on a timer interrupt, which uses Qt's Arthur Widgets. Arthur Widgets demos are implemented by Qt as a derived style class ArthurStyle and a generic frame class ArthurFrame, from which the actual demo program frames are derived. Both ArthurStyle and ArthurFrame are replicated in Haskell in the qtHaskell library and used by csPathDeform in an entirely analagous manner to that of the original Qt C++ "deform" demo program. This demonstrates that qtHaskell can be used to build generic objects/interfaces etc, derived from the basic Qt classes just as in C++. Also, use of the ArthurStyle class means that the callback functions are more resource intensive. The implementation of handlers in qtHaskell has been revised for this release, and the csPathDeform has a smoothness and responsiveness that is virtually indistinguishable from the C++ original. Enjoy! David Harley -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

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Haskell Weekly News: Issue 85 - September 13, 2008
by Brent Yorgey 14 Sep '08

14 Sep '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20080913 Issue 85 - September 13, 2008 --------------------------------------------------------------------------- Welcome to issue 85 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements citeproc-hs. Andrea Rossato [2]announced the first release of [3]citeproc-hs, a Haskell implementation of the [4]Citation Style Language. citeproc-hs adds a Bibtex-like citation and bibliographic formatting and generation facility to [5]Pandoc. Twidge. John Goerzen [6]announced the release of [7]Twidge, a command-line Twitter and Identi.ca client. Real World HAppS: Cabalized, Self-Demoing HAppS Tutorial (Version 3). Thomas Hartman [8]announced a new version of [9]happs-tutorial, with a correspondingly updated [10]online demo. generic list functions fixed. Jim Apple reported that genericTake, genericDrop, and genericSplitAt have [11]been fixed so they are now total functions (they used to fail on negative integer inputs, unlike their ungeneric counterparts). The Monad.Reader (13) - Call for copy. Wouter Swierstra [12]announced a call for copy for Issue 13 of the [13]Monad.Reader. The deadline for submitting articles is February 13, 2009. Heads Up: code.haskell.org is upgrading to darcs 2. Duncan Coutts [14]announced that /usr/bin/darcs on code.haskell.org will soon be upgraded to version 2. Most users should be unaffected as darcs 2 works just fine with repositories in darcs 1 format, and has been extensively tested for correctness. Discussion packages and QuickCheck. Conal Elliott [15]asked what methods of organization people use to package up QuickCheck tests for their libraries. Hackage needs a theme song!. Jason Dagit wrote a [16]theme song for Hackage! Jobs Gamr7. Lionel Barret De Nazaris [17]announced that [18]Gamr7, a startup in France focused on procedural city generation for the game and simulation market, is looking for a senior developer/technical director. senior role at Credit Suisse. Ganesh Sittampalam [19]announced that [20]Credit Suisse is seeking to recruit an expert in functional programming for a senior role in the Global Modelling and Analytics Group (GMAG) in the Securities Division. Blog noise [21]Haskell news from the [22]blogosphere. * Douglas M. Auclair (geophf): [23]What is declarative programming?. * John Goerzen (CosmicRay): [24]New Twitter Client: Twidge. * Mark Jason Dominus: [25]Return return. Mark's mind is blown by the code "return return" appearing in a paper by Mark Jones. * Eric Kow (kowey): [26]darcs weekly news #3. * Ketil Malde: [27]The FastQ file format for sequences. * >>> Nathan Sanders: [28]Real World Haskell. Nathan experiments with porting some of his Python code to Haskell. * Andrea Vezzosi (Saizan): [29]Results from GSoC. Andrea's GSoC work on a high-level dependency framework for Cabal is going to be released in a separate package for now, [30]hbuild. * >>> Ricky Clarkson: [31]An IRC Bot in Haskell, 20% code, 80% GRR. Ricky shares his experiences, frustrations, and eventual success writing a simple IRC bot in Haskell. * >>> Yaakov Nemoy: [32]Xmonad 0.8 released. * Luke Palmer: [33]The problem with Coq. ...is, according to Luke, that it doesn't have a nice graphical interface. * >>> James Cowie: [34]Haskell! yes no?. James dives into learning some Haskell. Verdict so far: a "very nice language". Quotes of the Week * EvilTerran: this is hard to express in this type system. i'm going to make my own type system instead! About the Haskell Weekly News New editions are posted to [35]the Haskell mailing list as well as to [36]the Haskell Sequence and [37]Planet Haskell. [38]RSS is also available, and headlines appear on [39]haskell.org. To help create new editions of this newsletter, please see the information on [40]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [41]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/44471 3. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/citeproc%2Dhs 4. http://xbiblio.sourceforge.net/csl/ 5. http://johnmacfarlane.net/pandoc/ 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/44453 7. http://software.complete.org/twidge 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/44410 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/happs-tutorial 10. http://happstutorial.com:5001/ 11. http://hackage.haskell.org/trac/ghc/ticket/2533 12. http://article.gmane.org/gmane.comp.lang.haskell.general/16420 13. http://www.haskell.org/haskellwiki/The_Monad.Reader 14. http://article.gmane.org/gmane.comp.lang.haskell.general/16419 15. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/44259 16. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/44450 17. http://article.gmane.org/gmane.comp.lang.haskell.cafe/44211 18. http://www.gamr7.com/ 19. http://article.gmane.org/gmane.comp.lang.haskell.general/16422 20. http://www.credit-suisse.com/ 21. http://planet.haskell.org/ 22. http://haskell.org/haskellwiki/Blog_articles 23. http://logicaltypes.blogspot.com/2008/09/what-is-declarative-programming.ht… 24. http://changelog.complete.org/posts/752-New-Twitter-Client-Twidge.html 25. http://blog.plover.com/prog/springschool95.html 26. http://koweycode.blogspot.com/2008/09/darcs-weekly-news-3.html 27. http://blog.malde.org/index.php/2008/09/09/the-fastq-file-format-for-sequen… 28. http://sandersn.com/blog/index.php?title=real_world_haskell 29. http://vezzosi.blogspot.com/2008/09/even-if-this-blog-has-been-silent-since… 30. http://hackage.haskell.org/trac/hackage/wiki/HBuild 31. http://rickyclarkson.blogspot.com/2008/09/irc-bot-in-haskell-20-code-80-grr… 32. http://loupgaroublond.blogspot.com/2008/09/xmonad-08-released.html 33. http://luqui.org/blog/archives/2008/09/07/the-problem-with-coq/ 34. http://www.jcowie.co.uk/2008/09/haskell-yes-no/ 35. http://www.haskell.org/mailman/listinfo/haskell 36. http://sequence.complete.org/ 37. http://planet.haskell.org/ 38. http://sequence.complete.org/node/feed 39. http://haskell.org/ 40. http://haskell.org/haskellwiki/HWN 41. http://code.haskell.org/~byorgey/code/hwn/

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job advert: senior role at Credit Suisse
by Sittampalam, Ganesh 12 Sep '08

12 Sep '08

Credit Suisse is seeking to recruit an expert in functional programming for a senior role in the Global Modelling and Analytics Group (GMAG) in the Securities Division. The group consists of about 140 people worldwide. The majority of the group are mathematicians engaged in developing mathematical models for financial products traded by the division. Approximately 20 people are primarily computing experts, based in the Architecture and Delivery (AD) subgroup within GMAG. The successful candidate will be based in the R&D section of AD (7 people), which focuses on projects designed to improve the productivity of the modellers. We are already making heavy use of functional programming within the group, primarily Haskell and F#, and we expect to increase this in the future. Some information about our Haskell projects can be found here: http://www.haskell.org/communities/05-2008/html/report.html#sect7.4; we have recently adopted F# for implementing and deploying models on the .NET platform. Our team will be working closely with the modellers to help them leverage functional programming to improve the design of their code. Key requirements: An exceptional academic track record in functional programming including a significant publication history. Significant experience of "real-world" computing environments, preferably using functional programming. Excellent communication skills in order to convey new ideas to our modelling team. Location: London or New York Contact: Howard Mansell <howard.mansell(a)credit-suisse.com> Howard and I will be attending ICFP 2008 and associated workshops - if you'd like to discuss this in person, get in touch with us by email (please email us both), or just grab one of us there. We'll also be talking about some of our Haskell work at ICFP and our F# work at CUFP. Background information: Credit Suisse provides investment banking, private banking and asset management services to clients across the world. Active in over fifty countries and employing more than 45,000 people, Credit Suisse is one of the world's premier banks. There are exceptional opportunities for further growth in new product areas and emerging markets; there are equally exceptional opportunities for the people who can deliver that growth. Credit Suisse offers intellectual challenges, high rewards and global development potential for individuals who share an enthusiasm for business-critical innovation. Credit Suisse provides investment banking, private banking and asset management services to clients across the world. Active in over fifty countries and employing more than 45,000 people, Credit Suisse is one of the world's premier banks. There are exceptional opportunities for further growth in new product areas and emerging markets; there are equally exceptional opportunities for the people who can deliver that growth. Credit Suisse offers intellectual challenges, high rewards and global development potential for individuals who share an enthusiasm for business-critical innovation. The Global Modelling and Analytics Group (GMAG) is responsible for producing state-of-the-art pricing, trading and risk management models for Credit Suisse. These models are used across a range of businesses in the Fixed Income and Equity departments. The group performs the full spectrum of quantitative work, from mathematical modelling through software implementation and delivery, to risk analysis of trades and existing portfolios. The group's mandate covers all major asset classes, including Credit Derivatives, Commodities, Emerging Markets, Equity Derivatives and Convertibles, Exotics, Foreign Exchange, Fund Linked Products, Interest Rate Products and Mortgage Derivatives. GMAG operates globally with over 140 members located in London, New York, Hong Kong, Tokyo, Wroclaw and São Paolo. Established in 1990, GMAG stands out as a unified quant group that has been covering all major product areas since its inception. The group has always enjoyed a strong relationship with Trading, Structuring and Sales, assisting them with trade pricing and risk management. As the group is based on the trading floor, it is ideally placed to respond to the financial modelling needs of the businesses it supports. The breadth of GMAG's mandate makes it uniquely positioned to leverage the skills and experience of its members, and to provide a consistent modelling approach across all areas. Over time, the group has developed an extensive suite of pricing models on a common platform with complete integration across all asset classes. Quantitative Analysts in GMAG carry out a range of activities which include the creation of sophisticated mathematical models for the valuation of complex derivatives, development of the technology platform used to deliver models and driving the use of these models throughout the bank. Our Quantitative Analysts typically hold an advanced quantitative degree, have excellent analytical and problem-solving skills, demonstrate creative thinking, have strong programming skills, and are confident communicators. ============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ==============================================================================

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Workshop on Generic Programming: Call for Participation (co-located w/ ICFP08)
by Matthew Fluet (ICFP Publicity Chair) 12 Sep '08

12 Sep '08

Dear all, the Workshop on Generic Programming is only a few days away: 20th September 2008 (http://www.regmaster.com/conf/icfp2008.html) ==> Invited talk: The Generic Paradigm ==> Lambert Meertens (Utrecht University) ==> We have reserved 20 minutes for *lightning talks*. If you plan to ==> attend and if you would like to give a short talk (about half-baked, ==> exciting, new stuff) please drop me a short note. Slots will be ==> reserved on a first-come-first-serve basis. Looking forward to seeing you in Victoria, Ralf Hinze ============================================================================ CALL FOR PARTICIPATION Workshop on Generic Programming 2008 Victoria, Canada, 20th September 2008 http://www.comlab.ox.ac.uk/ralf.hinze/wgp2008/cfp.{html,pdf,ps,txt} The Workshop on Generic Programming is sponsored by ACM SIGPLAN and forms part of ICFP 2008. Previous Workshops on Generic Programming have been held in Marstrand (affiliated with MPC), Ponte de Lima (affiliated with MPC), Nottingham (informal workshop), Dagstuhl (IFIP WG2.1 Working Conference), Oxford (informal workshop), Utrecht (informal workshop), and Portland (affiliated with ICFP). ============================================================================ Preliminary program ------------------- 9:00 - 10:00, Session Chair: Ralf Hinze (University of Oxford) Welcome Invited talk: The Generic Paradigm Lambert Meertens (Utrecht University) 10:30 - 12:00, Session Chair: Jeremy Gibbons (University of Oxford) A Functional Model-View-Controller Software Architecture for Command-oriented Programs Alley Stoughton (Kansas State University) A Lightweight Approach to Datatype-Generic Rewriting Thomas van Noort (Radboud University Nijmegen), Alexey Rodriguez, Stefan Holdermans (Utrecht University), Johan Jeuring (Utrecht University and Open University of the Netherlands), Bastiaan Heeren (Open University of the Netherlands) Lightning talks 13:30 - 15:00, Session Chair: Ralf Hinze (University of Oxford) Report from the program chair Ralf Hinze (University of Oxford) Scala for Generic Programmers Bruno C. d. S. Oliveira, Jeremy Gibbons (University of Oxford) A Comparison of C++ Concepts and Haskell Type Classes Jean-Philippe Bernardy, Patrik Jansson, Marcin Zalewski, Sibylle Schupp, Andreas Priesnitz (Chalmers University of Technology and University of Gothenburg) Lightning talks 15:30 - 17:30, Session Chair: Patrik Jansson (Chalmers University of Technology and University of Gothenburg) Polytypic Programming in Coq Wendy Verbruggen, Edsko de Vries, Arthur Hughes (Trinity College Dublin) Bialgebra Views: A Way for Polytypic Programming to Cohabit with Data Abstraction Pablo Nogueira, Juan Jose Moreno-Navarro (Universidad Politecnica de Madrid) Discussion ============================================================================

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The Monad.Reader (13) - Call for copy
by Wouter Swierstra 11 Sep '08

11 Sep '08

Call for Copy The Monad.Reader - Issue 13 You may want to pencil in the deadline for the next Monad.Reader: ** February 13, 2009 ** And in case you missed it, Issue 11 was released a few weeks ago with the following three articles: * David F. Place How to Refold a Map * Kenneth Knowles First-Order Logic a la Carte * Douglas M. Auclair MonadPlus: What a Super Monad! Check it out at http://www.haskell.org/haskellwiki/The_Monad.Reader * About the Monad.Reader * The Monad.Reader is an electronic magazine about all things Haskell. It is less formal than journal, but more enduring than a wiki-page or blog. There have been a wide variety of articles, ranging from code fragments, puzzles, book reviews, tutorials, to half-baked research ideas. * Submission Details * Get in touch with me if you intend to submit something - the sooner you let me know what you're up to, the better. Please submit articles for the next issue to me by e-mail (wss at cs.nott.ac.uk). Articles should be written according to the guidelines available from http://www.haskell.org/haskellwiki/The_Monad.Reader Please submit your article in PDF, together with any source files you used. The sources will be released together with the magazine under a BSD license. If you would like to submit an article, but have trouble with LaTeX please let me know and we'll sort something out. All the best, Wouter This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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Heads Up: code.haskell.org is upgrading to darcs 2
by Duncan Coutts 11 Sep '08

11 Sep '08

This email is for darcs users in general and in particular for people who host a project on code.haskell.org. What we are doing ================= We are upgrading /usr/bin/darcs to version 2 on the machine that hosts code.haskell.org. That means it will be used by everyone who uses ssh to push or pull from a darcs repository on code.haskell.org. Pulling via http is completely unaffected. Do I have to do anything? ========================= No. You do not have to change anything. darcs v2 can talk to darcs v1 clients perfectly well so you do not need to upgrade your local version of darcs. You do not need to change the format of your local or server-side repositories. Darcs v2 works fine with darcs v1 format repositories. Should I change anything? ========================= We recommend that you upgrade your local darcs to version 2. This will allow you to take advantage of substantially faster push/pull operations over ssh (darcs 2 makes far fewer ssh connections). As noted above however it is not necessary for you to upgrade or for you to synchronise your upgrading with anyone else who uses the same repository. It is also possible to use a darcs "v1.5" hashed format locally and continue to use darcs v1 format on the server side. This has some performance and reliability advantages. Again this is something you can decide yourself without coordinating with other users of the repository. If your development style means that you bump into the infamous merging problems with darcs v1 format then you may consider converting your repository to the darcs v2 format. Remember that using darcs 2 with darcs v1 format repositories does not eliminate the merging issue. To banish the merging problems you have to use the darcs v2 format. This is however a more substantial change and has to be synchronised between users of the repository because it involves converting the server side repository to v2 format and all users getting the repository again. So if merging is an issue for you then you should discuss it with other users of your repository. Is this change safe? ==================== Yes. Darcs 2 has a substantial test suite. It has unit tests covering the core patch operations and also over 100 scripts doing functional testing, including network tests. The darcs build-bots run all these tests on all the popular platforms. Additionally, the code in darcs 2 for handling the v1 format is mostly the same as in darcs 1, so there are no big risks in using darcs 2 while continuing to use darcs v1 format repositories. The main change in the v1 format code is bug fixes, instrumentation code for debugging/introspection and more cunning types in the patch handling code that enforces some of the patch invariants. Furthermore, we have done real world tests using copies of all the 153 repositories on code.haskell.org which comes to around 2GB. We wanted to verify a couple things: 1. that using darcs 1 on the client and darcs 2 on the server works fine to pull and push patches. This corresponds to a project where all the users are still using darcs 1. 2. that using a mixture of darcs 1 and darcs 2 clients works when pushing and pulling patches between the clients via the server. This corresponds to a project where some users have upgraded but others have not yet. We tested with darcs 1.0.9 and 2.0.2 in three combinations: client darcs 1, server darcs 1 client darcs 1, server darcs 2 client darcs 2, server darcs 2 The test consisted of obliterating a significant number of patches from each repository and pushing them back. In a separate experiment each repository was converted to darcs v2 format which worked without problem in every case. What if I have problems? ======================== Contact support(a)community.haskell.org. We have made backups of all the repositories in case there are any critical problems. Thanks to the darcs hackers Eric Kow and Jason Dagit for doing all the hard testing work. Duncan, Ian and Malcolm (part of the community server admin team)

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CC 2009: abstracts due Oct 2
by Oege.de.Moor＠comlab.ox.ac.uk 10 Sep '08

10 Sep '08

>>> abstracts - Oct 2, full papers - Oct 9 <<< CC 2009 International Conference on Compiler Construction March 22-29, York, United Kingdom Invited Speaker: Vivek Sarkar (Rice University, US) Part of ETAPS 2009 http://www.brics.dk/~mis/CC2009/ CC is a premier forum for presenting research on compilers in the broadest possible sense, including run-time techniques, programming tools, domain-specific languages, novel language constructs and so on. In recent years CC has seen a healthy increase in the number of submissions, in line with its broad outlook; its typical acceptance rate is 20-25%. CC is part of ETAPS, and this year it is held in York (UK), March 22-29 2009. The program committee would particularly welcome submissions from researchers in functional programming on any topic relating to analysis, optimisation and compilation of Haskell programs Abstracts are due on October 2, and the deadline for full paper submission is October 9. Prospective authors are welcome to contact the program chairs, Michael Schwartzbach (mis(a)brics.dk) and Oege de Moor (oege(a)comlab.ox.ac.uk) with any queries they might have.

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