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CALL FOR Workshop Proposals (ICFEM 2011)
by Huibiao Zhu 13 Feb '11

13 Feb '11

************************************************************ ICFEM 2011: 13th International Conference on Formal Engineering Methods CALL FOR Workshop Proposals 25-28 Oct 2011 Radisson BLU Hotel, Durham, UK URL: http://www.scm.tees.ac.uk/icfem2011 ************************************************************ Since 1997, ICFEM has provided a forum for those interested in the application of formal engineering methods to computer systems. Researchers and practitioners, from industry, academia, and government, are encouraged to attend, and to help advance the state of the art. In 2011 the 13th International Conference on Formal Engineering Methods (ICFEM 2011), which is being sponsored and organised by Teesside University, will be held at the Radisson BLU hotel in Durham, UK, from the 25th to 28th October 2011. The first day, 25 October 2011, will be dedicated to workshops and other satellite events, while the ICFEM 2011 conference proper will occupy the subsequent three days, 26-28 October 2011. The organizing committee of ICFEM 2011 therefore cordially invites proposals for one-day workshops in any area of formal methods and software engineering, but particularly in new or emerging fields of application of formal methods and on experience with practical application domains of formal methods. Submission of Proposals Proposals for workshops should contain * a title and brief description of the workshop topic; * the names and contact details of the potential organisers; * a brief justification of the topic and estimated size of audience * a description of any special technical requirements Proposals should be sent to ICFEM2011 Workshops Chair, Steve Dunne, at s.e.dunne(a)tees.ac.uk no later than 10 March 2011.

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ANNOUNCE: Save the date! Haskell hackathon in Philadelphia, July 29-31
by Brent Yorgey 12 Feb '11

12 Feb '11

I am very pleased to announce that Hac phi 3, third in an annual series of Haskell hackathons hosted at the University of Pennsylvania in Philadelphia, will take place from July 29-31. More details will be forthcoming, but put it on your calendar now. The past two years have been a blast -- you won't want to miss this one! Q: Do I have to already be a Haskell expert to attend? A: No! All are welcome. In fact, sitting in a room with a bunch of enthusiastic Haskell hackers is a great way to learn. Past attendees have included seasoned Haskell gurus and raw beginners alike. Q: What does one do at a Haskell hackathon? A: The goal is to create a fun, interactive, collaborative environment for writing Haskell code. You can work on a project of your own, or help someone else with theirs. Q: What will the cost be? A: We're still working out the details, but as in past years, registration will be free, and we hope to be able to provide some of the meals. You'll be on your own for transportation and lodging. The Hac Phi team: Chris Casinghino (ccasin) Daniel Wagner (dmwit) Brent Yorgey (byorgey)

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Beginner - Binary Search Tree Question
by htc2011 12 Feb '11

12 Feb '11

Hi All, I am learning Haskell and can't understand the following problem. Maybe somebody could advise me on a solution? Using GHCI, I have the following definition of a BST: data Ord a => BST a = EmptyBST | Node ( BST a ) a ( BST a ) deriving (Show) I want to determine the number of leaves that a tree using the above definition has: numLeaves :: Ord a => BST a -> Int numLeaves EmptyBST = 0 numLeaves (Node b a c) | b == EmptyBST = 1 + numLeaves c | c == EmptyBST = 1 + numLeaves b | otherwise = numLeaves b + numLeaves c However whenever I load my haskell file containing the above code into GHCI, I get the following error: Could not deduce (Eq (BST a)) from the context (Ord a) arising from a use of `==' at a8.hs:17:3-15 Possible fix: add (Eq (BST a)) to the context of the type signature for `numLeaves' or add an instance declaration for (Eq (BST a)) In the expression: b == EmptyBST In a stmt of a pattern guard for the definition of `numLeaves': b == EmptyBST In the definition of `numLeaves': numLeaves (Node b a c) | b == EmptyBST = 1 + numLeaves c | c == EmptyBST = 1 + numLeaves b | otherwise = numLeaves b + numLeaves c Could anybody explain to me what this means? / How to get around this? Thank you for your time! -- View this message in context: http://haskell.1045720.n5.nabble.com/Beginner-Binary-Search-Tree-Question-t… Sent from the Haskell - Haskell mailing list archive at Nabble.com.

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#haskell-game & Haskellers Game Interest Group
by Korcan Hussein 12 Feb '11

12 Feb '11

Some of us interested in Haskell GameDev have formed chat room & Haskellers Interest Group, you can out find more info here. Just spreading the word around.

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ANNOUNCE: hspec-0.1.0 (Behavior Driven Development for Haskell)
by trystan.s＠comcast.net 12 Feb '11

12 Feb '11

hspec - Behavior Driven Development for Haskell hspec ties together requirements and code that verifies the requirements are met. The verifying code can be a boolean expression, a QuickCheck property, or an explination of why it's pending. The requirements can then be turned into documentation of what the code does and what remains to be implemented. hspec verifies its own requirements as an example of how to use it. You can find the code on github: https://github.com/trystan/hspec There's also a cabal generated tar.gz: https://github.com/downloads/trystan/hspec/hspec-0.1.0.tar.gz I'll add it to hackageDB when I get a user name.... And here it is in action: Step 1, define some requirements ]> import Test.Hspec ]> ]> specs :: IO [Spec] ]> specs = describe "quantify" [ ]> it "returns the singular form of a word when given the number 1" ]> (quantify 1 "thing" == "1 thing"), ]> ]> it "returns the plural form of a word when given a number greater than 1" ]> (quantify 2 "thing" == "2 things"), ]> ]> it "returns the plural form of a word when given the number 0" ]> (quantify 0 "thing" == "0 things"), ]> ]> it "handles describing the plural of words that end with an 'x'" ]> (pending "no need for this yet") ]> ] Step 2, make it compile ]> quantify _ _ = "" Step 3, watch your requirements fail ]> hspec specs quantify x returns the singular form of a word when given the number 1 x returns the plural form of a word when given a number greater than 1 x returns the plural form of a word when given the number 0 - handles describing the plural of words that end with an 'x' # no need for this yet Finished in 0.001 seconds 4 examples, 3 failures Step 4, make it right ]> quantify :: Int -> String -> String ]> quantify 1 s = "1 " ++ s ]> quantify n s = show n ++ " " ++ s ++ "s" Step 5, watch your requirements pass ]> hspec specs quantify - returns the singular form of a word when given the number 1 - returns the plural form of a word when given a number greater than 1 - returns the plural form of a word when given the number 0 - handles describing the plural of words that end with an 'x' # no need for this yet Finished in 0.001 seconds 4 examples, 3 failures Any advice, comments, or questions are welcome. Trystan Spangler

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SICSA PhD Studentships in Scotland
by Kevin Hammond 11 Feb '11

11 Feb '11

Ph.D. Studentships, Scottish Universities The Scottish Informatics and Computer Science Alliance (http://www.sicsa.ac.uk) invites applications for up to 20 international prize studentships from outstanding PhD candidates to Scottish universities. The studentships are open to citizens and residents of any country. SICSA studentships cover living costs and fees at the UK/EU level and successful candidates may apply for further fee support. We will consider applicants in any area of computer science and informatics but may give preference to students who are working in SICSA theme areas: Students must have or must expect to be awarded a 1st class honours degree or an MSc with Distinction or equivalent GPA scores. Your degree must be in a discipline that is relevant to your proposed field of research. For more details of how to apply for a SICSA prize studentship, see the SICSA web pages (http://www.sicsa.ac.uk/graduate-academy/prize-studentships/applying-for-a-s…) The deadline for applications is 28th February 2011. Please contact me in the first instance if you are interested: our research usually comes either under the modelling and abstraction or complex systems engineering themes. Best Wishes, Kevin -------- Kevin Hammond, Professor of Computer Science, University of St Andrews T: +44-1334 463241 F: +44-1334-463278 W: http://www.cs.st-andrews.ac.uk/~kh In accordance with University policy on electronic mail, this email reflects the opinions of the individual concerned, may contain confidential or copyright information that should not be copied or distributed without permission, may be of a private or personal nature unless explicitly indicated otherwise, and should not under any circumstances be taken as an official statement of University policy or procedure (see http://www.st-and.ac.uk) The University of St Andrews is a charity registered in Scotland : No SC013532

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ANNOUNCE: darcs 2.5.1
by Ganesh Sittampalam 10 Feb '11

10 Feb '11

Hi, The darcs team is pleased to announce the release of darcs 2.5.1, a minor upgrade for the 2.5 release. The main focus of this release is support for the GHC 7.0 series and the upcoming February 2011 Haskell Platform, but the release also includes a few bug fixes and minor usability improvements. A detailed changelog is below. Installing ---------- The easiest way to install darcs 2.5.1 from source is by first installing the Haskell Platform (http://www.haskell.org/platform) If you have installed the Haskell Platform or cabal-install, you can install this release by doing: $ cabal update $ cabal install darcs-2.5.1 Alternatively, you can download the tarball from http://darcs.net/releases/darcs-2.5.1.tar.gz and build it by hand as explained in the README file. Versions of GHC from 6.10.x to 7.0.x are supported. The 2.5 branch is also available as a darcs repository from http://darcs.net/releases/branch-2.5 Binaries -------- These will be posted to http://wiki.darcs.net/Binaries as they become available. Reporting bugs -------------- If you have an issue with darcs 2.5.1, you can report it via the web on http://bugs.darcs.net/ . You can also report bugs by email to bugs at darcs.net. Changelog --------- * Include original text in conflict marks Conflicts are now marked up as v v v v v v v original text before any conflicting patch ============= conflicting result A ************* conflicting result B .... ^ ^ ^ ^ ^ ^ ^ The inclusion of the original text makes it much easier to understand what the changes on either side of the conflict were. This is only an incremental improvement to our conflict marking, which we understand is still hard to use. More substantial improvements are in the works. * Support GHC 7.0 and various recent library versions (http://bugs.darcs.net/issue2008, http://bugs.darcs.net/issue2019) This should mean that darcs 2.5.1 will work with the upcoming Feb 2011 Haskell Platform release. * Restrict the GHC version in the cabal file This means that cabal builds will explicitly fail if an unsupported GHC version is encountered, which should cause less user confusion. * Update warning message about old-fashioned repositories It now points to a wiki page explaining our deprecation plan (http://wiki.darcs.net/OF) * Guard against non-repository paths during get (http://bugs.darcs.net/issue2035) Darcs normally checks for paths that point outside the repository when applying patches, but this check was missing in the case of get. * Darcs library API: make the "program name" configurable This makes it easier for external users of the library API to reuse Darcs' framework for handling commands. * darcs send now prints the remote repository address up front Previously it would first read the remote repository, which made it hard to see what was happening when accessing the remote repository hung. * Informational message about --set-default is now disabled by explicit use of --no-set-default (http://bugs.darcs.net/issue2003) This allows users to silence the message by placing 'pull no-set-default', 'push no-set-default' and 'send no-set-default' in ~/.darcs/defaults or _darcs/prefs/defaults. * Handle _darcs/format correctly on get (http://bugs.darcs.net/issue1978) This is mainly a forwards compatibility issue as no existing version of darcs would create format files that are affected by this bug. * Fix linking with libdarcs on Windows (http://bugs.darcs.net/issue2015) This was a simple problem with a missing object file.

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ANN: iteratee-0.7.0.2 and 0.8.0.1 released
by John Lato 10 Feb '11

10 Feb '11

(Apologies for cross-posting) I have recently discovered a memory leak which affects all current versions of iteratee. I have released iteratee versions 0.7.0.2 and 0.8.0.1 which fixes the memory leak. I would strongly encourage all users of earlier versions to upgrade to one of these releases. Cheers, John Lato

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Haskell Weekly News: Issue 168 - February 09, 2011
by Daniel Santa Cruz 10 Feb '11

10 Feb '11

Welcome to issue 168 of the HWN, a newsletter covering developments in the [1]Haskell community. This release covers the week of January 30 to February 5, 2011. Announcements Maciej Piechotka [2]announced version 0.1.1 of nanoparsec. "Nanoparsec is currently simply a port of attoparsec on ListLike (the abstraction of lists used by iteratee)." Graham Hutton [3]announced the availability of studenships in Functional Programming at the University of Nottingham, UK. Ashley Yakeley [4]made a small update to time (1.2.0.4) that "fixes a bug in parseTime." George Giorgidze [5]announced the release to Hackage of Database Supported Haskell (DSH). Simon Hengel [6]announced the release of HackageOneFive, "a tiny Snap app that provides reverse dependency lookup for all packages on Hackage." Quotes of the Week * alpounet: map succ/pred is a scandinavian name generator or what? ... well, scandinavian and aztec * dons: Think of a monad as a spacesuit full of nuclear waste in the ocean next to a container of apples. Now, you can't put oranges in the space suite or the nuclear waste falls in the ocean, *but* the apples are carried around anyway, and you just take what you need. * Apocalisp: a unit of clarity is a clarinet * roconnor: My coq has failed me * roconnor: I mean, I could, and do, say that a lens is just a monoid natural transformation from the coalgebra functiors from haskell functors to haskell types. * Saizan: "not being ML" is a quite sound principle syntax-wise * lpsmith: well, getting rid of airliners certainly *is* one way of eliminating their potential use as weapons against larger buildings * ddarius: The reason edwardk writes so many Haskell packages is to ward the Perl from penetrating his heart. * monochrom: most people tend to deny the usefulness of useful alternative perspectives --- their entrenched vested interests demand it. as they grow older they also have more influence and power over "the state of the art" to preserve their self-fulfilling prophecy that "the alternative is useless" --- by controlling what practice looks like, they can control what looks useless. * edwardk: i learned to program becaise i'd lied and told a kid that i'd written a disassembler, then had to make good on the claim. Top Reddit Stories * Quine Central ... because everyone needs to be able to make nth order quines Domain: blog.sigfpe.com, Score: 40, Comments: 7 On Reddit: http://www.reddit.com/r/haskell/comments/fc4cs/quine_central_because_everyo… Original: http://blog.sigfpe.com/2011/01/quine-central.html * jhc 0.7.7 is out Domain: haskell.org, Score: 38, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/fbqo7/jhc_077_is_out/ Original: http://www.haskell.org/pipermail/jhc/2011-January/000874.html * Hulk: A Haskell IRC server Domain: chrisdone.com, Score: 32, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/fbrie/hulk_a_haskell_irc_server/ Original: http://chrisdone.com/posts/2011-01-30-hulk-haskell-irc-server.html * Status update on {code, trac, projects, planet, community}.haskell.org Domain: haskell.org, Score: 25, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/fdnjp/status_update_on_code_trac_p… Original: http://www.haskell.org/pipermail/haskell-cafe/2011-February/088829.html * All about MVars : Inside T5 Domain: blog.ezyang.com, Score: 23, Comments: 4 On Reddit: http://www.reddit.com/r/haskell/comments/fduxb/all_about_mvars_inside_t5/ Original: http://blog.ezyang.com/2011/02/all-about-mvars/ * Text: a visual programming language based on Haskell, demo Domain: vimeo.com, Score: 21, Comments: 3 On Reddit: http://www.reddit.com/r/haskell/comments/fbgxd/text_a_visual_programming_la… Original: http://vimeo.com/19273744 * [SO] Why is GHC so big? Domain: stackoverflow.com, Score: 21, Comments: 10 On Reddit: http://www.reddit.com/r/haskell/comments/fczht/so_why_is_ghc_so_big/ Original: http://stackoverflow.com/questions/4858585/why-is-ghc-so-large-big * Haskell Weekly News: Issue 167 Domain: contemplatecode.blogspot.com, Score: 21, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/fe63a/haskell_weekly_news_issue_16… Original: http://contemplatecode.blogspot.com/2011/02/haskell-weekly-news-issue-167.h… * The F# Team are Hiring (functional programming jobs) Domain: haskell.org, Score: 20, Comments: 6 On Reddit: http://www.reddit.com/r/haskell/comments/fcvec/the_f_team_are_hiring_functi… Original: http://www.haskell.org/pipermail/haskell/2011-January/022523.html * Recently Uploaded: DSH-0.4.2 Natural Sql Queries without the need to write Sql strings. Domain: hackage.haskell.org, Score: 20, Comments: 2 On Reddit: http://www.reddit.com/r/haskell/comments/fesjj/recently_uploaded_dsh042_nat… Original: http://hackage.haskell.org/package/DSH * Specifying behaviors in a purely functional language Domain: io7m.com, Score: 16, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/fdvux/specifying_behaviors_in_a_pu… Original: http://io7m.com/articles/itefs/ Top StackOverflow Answers * Why is GHC so large/big? votes: 29 Read on SO: http://stackoverflow.com/questions/4858585/why-is-ghc-so-large-big/4867236#… It's a bit silly really. Every library that comes with GHC is provided in no less than 4 flavours: static dynamic profiled GHCi The GHCi version is just the static version linked together in a single .o file. The other three versions all have their own set of interface files (.hi files) too. The profiled versions seem to be about twice the size of the ... * Why `(map digitToInt) . show` is so fast? votes: 24 Read on SO: http://stackoverflow.com/questions/4841078/why-map-digittoint-show-is-so-fa… Seeing as I can't add comments yet, I'll do a little bit more work and just analyze all of them. I'm putting the analysis at the top; however, the relevant data is below. (Note: all of this is done in 6.12.3 as well - no GHC 7 magic yet.) Analysis: Version 1: show is pretty good for ints, especially those as short as we have. Making strings actually ... * What Justification for the type of f x = f x in Haskell is there? votes: 15 Read on SO: http://stackoverflow.com/questions/4847008/what-justification-for-the-type-… Okay, starting from the function definition f x = f x, let's step through and see what we can deduce about the type of f. Start with a completely unspecified type variable, a. Can we deduce more than that? Yes, we observe that f is a function taking one argument, so we can change a into a function between two unknown type variables, which we'll call b -> ... * . versus $ in haskell votes: 14 Read on SO: http://stackoverflow.com/questions/4876828/versus-in-haskell/4876900#4876900 Prelude> :t ($) ($) :: (a -> b) -> a -> b Prelude> :t (.) (.) :: (b -> c) -> (a -> b) -> a -> c $ applies a function to a value. . composes two functions. So I can write f $ g x which is "apply f to (g of x)" or f . g $ x which is "apply the composition of f and g to x". One common style is to pile up dots on the left with a ... * Starting a game development in an exotic language I am just learning (Lisp, Haskell, ...) votes: 12 Read on SO: http://stackoverflow.com/questions/4867656/starting-a-game-development-in-a… If you could write a game in C, you can write one in Haskell. The biggest difficulties many people have with it are: Lack of support for OOP, which is what most people are familiar with these days. Old-fashioned procedural code, on the other hand, is actually very pleasant to write in Haskell; the IO type distinguishes effect-free functions from procedures ... * Haskell: Check if Int is in a list of Int's votes: 11 Read on SO: http://stackoverflow.com/questions/4846974/haskell-check-if-int-is-in-a-lis… First find the type of the function you need. To "Check if" means to return either True or False, a Bool. So the function takes an Int, a list of Int (aka [Int]) and returns Bool: Int -> [Int] -> Bool Now ask hoogle. elem :: Eq a => a -> [a] -> Bool Hoogle is a very useful tool. You can integrate it with ghci. Top StackOverflow Questions * Why is GHC so large/big? votes: 32, answers: 5 Read on SO: http://stackoverflow.com/questions/4858585/why-is-ghc-so-large-big * Starting a game development in an exotic language I am just learning (Lisp, Haskell, …) votes: 16, answers: 10 Read on SO: http://stackoverflow.com/questions/4867656/starting-a-game-development-in-a… * Why `(map digitToInt) . show` is so fast? votes: 8, answers: 2 Read on SO: http://stackoverflow.com/questions/4841078/why-map-digittoint-show-is-so-fa… * Transforming expression given in prefix notation, identifying common subexpressions and dependencies votes: 7, answers: 6 Read on SO: http://stackoverflow.com/questions/4843237/transforming-expression-given-in… * Practical use of curried functions? votes: 7, answers: 6 Read on SO: http://stackoverflow.com/questions/4888480/practical-use-of-curried-functio… About the Haskell Weekly News You can find an html version of this newsletter at: http://contemplatecode.blogspot.com/2011/02/haskell-weekly-news-issue-168.h… To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. I'm in dire need of finding good "quotes of the week". If you happen to come across any, please don't hesitate to send it along. Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/85781 3. https://groups.google.com/d/topic/fa.haskell/rURgYMjEZhU/discussion 4. https://groups.google.com/d/topic/fa.haskell/l-I05W30DWU/discussion 5. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/85961 6. https://groups.google.com/d/topic/fa.haskell/vp2P5w8GbkM/discussion

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ANN: listlike-instances
by John Lato 09 Feb '11

09 Feb '11

Hello, I am pleased to announce the first release of listlike-instances. The listlike-instances package provides orphan ListLike instances for strict and lazy Text[0], and regular, storable, and unboxed Vectors[1]. These class instances greatly expand the available options for ListLike users. John [0] http://hackage.haskell.org/package/text [1] http://hackage.haskell.org/package/vector

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