March 2009 - Haskell - Haskell.org

Announcing Djinn, version 2004-12-11, a coding wizard
by Lennart Augustsson 07 Apr '11

07 Apr '11

Howdy, y'all! I've written a small program that takes a (Haskell) type and gives you back a function of that type if one exists. It's kind of fun, so I thought I'd share it. It's probably best explained with a sample session. 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. To play with Djinn do a darcs get http://darcs.augustsson.net/Darcs/Djinn or get http://darcs.augustsson.net/Darcs/Djinn/Djinn.tar.gz Then just type make. (You need a Haskell 98 implementation and some libraries.) And then start djinn. For the curious, Djinn uses a decision procedure for intuitionistic propositional calculus due to Roy Dyckhoff. It's a variation of Gentzen's LJ system. This means that (in theory) Djinn will always find a function if one exists, and if one doesn't exist Djinn will terminate telling you so. This is the very first version, so expect bugs. :) Share and enjoy. -- Lennart

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ANNOUNCE: ChristmasTree 0.1 (excuses for second attempt)
by S.Doaitse Swierstra 07 Jul '09

07 Jul '09

We are pleased to announce the availability of the package "ChristmasTree", which contains the code associated with our paper at the last Haskell symposium: @inproceedings{1411296, author = {Marcos Viera and S. Doaitse Swierstra and Eelco Lempsink}, title = {Haskell, do you read me?: constructing and composing efficient top-down parsers at runtime}, booktitle = {Haskell '08: Proceedings of the first ACM SIGPLAN symposium on Haskell}, year = {2008}, isbn = {978-1-60558-064-7}, pages = {63--74}, location = {Victoria, BC, Canada}, doi = {http://doi.acm.org/10.1145/1411286.1411296}, publisher = {ACM}, address = {New York, NY, USA}, } The name of the package stands for: "Changing Haskell's Read Implementation Such That by Manipulating Abstract Syntax Trees it Reads Expressions Efficiently" which, given the time of year, seems appropriate. Feel free to download and unpack this "present" at what for the Dutch is called "Sinterklaasavond" (http://en.wikipedia.org/wiki/Sinterklaas) Arthur Baars Marcos Viera Eelco Lempsink Doaitse Swierstra PS: the package uses our library supporting transformation of typed abstract syntax, which we placed in a separate package TTTAS

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[ANN] Safe Lazy IO in Haskell
by Nicolas Pouillard 18 May '09

18 May '09

Hi folks, We have good news (nevertheless we hope) for all the lazy guys standing there. Since their birth, lazy IOs have been a great way to modularly leverage all the good things we have with *pure*, *lazy*, *Haskell* functions to the real world of files. We are happy to present the safe-lazy-io package [1] that does exactly this and is going to be explained and motivated in the rest of this post. === The context === Although these times were hard with the Lazy/IO technique, some people continue to defend them arguing that all discovered problems about it was not that harmful and that taking care was sufficient. Indeed some issues have been discovered about Lazy/IOs, some have been fixed in the underlying machinery, some have just been hidden and some others are still around. == An alternative == An alternative design has been proposed --and is still evolving--, it is called "Iteratee" [2] and has been designed by Oleg Kiselyov. This new design has tons of advantages over standard imperative IOs, and shares some of the goals of Lazy/IOs. Iteratee provides a way to do incremental processing in a high-level style. Indeed both processed data (via enumerators) and processing code (called iteratee) can be modularly composed. The handling of file-system resources is precise and safe. Catching errors can be done precisely and can be interleaved with the processing. In spite of all this, there is an important drawback: a lot of code has to be re-written and thought in another way. Processing becomes explicitly chunked which is not always needed and, even worse, exceptions handling also becomes very explicit. While this makes sense in a wide range of applications it makes things less natural than the general case of pure functions. We think that Iteratee have too be studied more, and we recommend them when you have incrementally react to IO errors. == Issues of Standard Lazy/IO == We think that we can save Lazy/IO cheaply, but before explaining the way we solve such and such issue, let's first expose Lazy/IO and its issues. One of the main Lazy/IO functions is 'readFile': it takes a file path opens it and returns the list of characters until the end of the file is reached. The characteristic of 'readFile' is that only the opening is done strictly, while the reading is performed lazily as much as the output list is processed. Cousins of 'readFile' are 'hGetContents' that takes a file handle and 'getContents' that reads on the standard input. This technique enables to process a file as if the file was completely stored in memory. Because it is read lazily one knows that only the required part of the file will be read. Even better, if the input is consumed to produce a small output or the output is emitted incrementally, then the processing can be done in constant memory space. Examples: -- Prints the number of words read on stdin > countWords = print . length . words =<< getContents -- Prints the length of the longest line > maxLineLen = print . maximum . map length . lines =<< getContents -- Prints in lower case the text read on stdin > lowerText = interact (map toLower) -- Alternatively > lowerText = putStr . map toLower =<< getContents All these examples are pretty idiomatic Haskell code and make a simple use of Lazy/IOs. Each of them runs in constant memory space even if they are declared as if the whole contents were available at once. By using stream fusion or 'ByteString''s one can get even faster code while keeping the code almost the same. Here we will stay with the default list of 'Char''s data type. However one goal of our approach is to be trivially adaptable to those data types. Using our library will be rougly a matter of namespace switch plus a running function: > lowerText = LI.run' (SIO.putStr . map toLower <$> LI.getContents) However we will introducing this library as one goes along. Here is another example where the Lazy/IO are still easy to use but no longer scales well. This program counts the lines of all the files given in arguments: > countLines = print . length . lines . concat =<< mapM readFile =<< getArgs Here the problem is the limitation of simultaneous opened files. Indeed, all the files are opened at the beginning therefore reaching the limit easily. It's time to recall when the files are closed. With standard Lazy/IOs the handle is closed when you reach the end of the file, and so when you've explored the whole list returned by 'readFile'. Note also that if you manually open the file and get a handle, then you can manually close the file, however if by misfortune you close the file and then still consume the lazy list you will get a truncated list, observing how much of the file has been read. This last point is due to the fact that 'readFile' considers the reading error as the end of the file. In particular one can fix this program, by simply counting the number of lines of each file separately and then compute the sum to get the final result. > countLines = print . sum =<< mapM (fmap (length . lines) . readFile) =<< getArgs However once again this program exhausts the handle resources. Trying to close the files will not save us either, one just risks getting truncated files. Indeed the list of intermediate results is produced eagerly but each intermediate result is lazy and then each file is opened but not immediately closed since the computation is delayed. Hopefully adding a bit of strictness cures the problem: > countLines = print . sum =<< mapM ((return' . length . lines =<<) . readFile) =<< getArgs > where return' x = x `seq` return x Until there, we have disclosed three problems: * while reading is lazy, opening is strict, which leads to a less natural processing of multiple files * the closing of files is hard to predict * the errors during reading are silently discarded The last one is a bit trickier and has recently been exposed by Oleg Kiselyov [3]. The problem appears when one gets twice the contents of the same stream---or some kind of inter-dependent streams. Because reading is implicitly driven by the consumer, the interleaving of reading may then depend on the reduction strategy employed. This is the case even if the consumer is a pure function. Basically in this example one can observe different values when using one of these functions: > f1 x y = x `seq` y `seq` x - y > f2 x y = y `seq` x `seq` x - y In this example one reads stdin twice and relies on the error handling to end one stream while keeping the other opened. Moreover there are other ways to achieve this like the use of unix fifo files, or using 'getChanContents' from the "Control.Concurrent.Chan" module. === Our solution === Here we will present another design, based on a very simple idea. Our goal is to provide IO processing in a style very similar to standard Lazy/IO with the following differences: - preservation of the determinism; - a simple control exceptions; - and a precise management of resources. Our solution is made of three key ingredients: a bit of strictness, some predefined schemas to interleave inputs, some scopes and abstract types to delimit lazy input operations from strict IO operations. == Dealing with a single input == Let's present the first ingredient alone through a first example: > mapHandleContents :: NFData sa => Handle -> (String -> sa) -> IO sa > mapHandleContents h f = do > s <- hGetContents h > return' (f s) `finally` hClose h > return' :: (Monad m, NFData sa) => sa -> m sa > return' x = rnf x `seq` return x It implements some combination of 'fmap' and 'hGetContents'. Actually some of our examples fit nicely in that model: > countWords = print =<< mapHandleContents stdin (length . words) > maxLineLen = print =<< mapHandleContents stdin (maximum . map length . lines) > lowerText = putStr =<< mapHandleContents stdin (map toLower) However while the two first examples work well in this setting, the third one tries to allocate the whole result in memory before printing it. Here the ingredient that is used is strictness: the purpose in forcing the result is to be sure that all the needed input is read, before the file is closed. So here we rely on 'NFData' instances to really perform deep forcing---this kind of assumption is a bit like 'Typeable' instances. In particular functions must not be an instance of 'NFData': indeed, we have no way to force lazy values that are stored in the closure of a function. The same remark applies to the 'IO' monad for at least three reasons: 'IO' if often represented by functions; lazy 'IORef''s could be used to hide one input for later use; exceptions with a lazy contents could also be used to make a lazy value escape. Let's now add some more strictness into the meal: the 'SIO' monad! == The 'SIO' monad == The 'SIO' monad is a thin layer over the 'IO' monad, populated only by strict 'IO' operations. In particular these operations are strict in the output, which means that once the output is produced then we know that the given arguments cannot be further evaluated/forced. Here is an example of strict IO using the 'SIO' monad: > import qualified System.IO.Strict as SIO > import System.IO.Strict (SIO) > countWords = SIO.run (SIO.print . length . words =<< SIO.getContents) Of course this function does not scale well since it reads the whole contents in memory before processing it. For now the strict-io [4] package contains wrappers for functions in "System.IO", and strict 'IORef''s. One can now introduce a function in lines of 'mapHandleContents': > withHandleContents :: NFData sa => Handle -> (String -> SIO sa) -> IO sa > withHandleContents h f = do > s <- hGetContents h > SIO.run (f s) `finally` hClose h One can then rewrite 'lowerText' as follow: > lowerText = withHandleContents stdin (SIO.putStr . map toLower) Until there one can deal quite nicely with single input, many outputs processing. Currently the only requirement is to delimit a scope where the resource will be used to return a strict value. Dealing with multiple inputs will lead us to our final design of lazy inputs. == Introducing 'LI', Lazy Inputs == We first introduce a type for these lazy inputs namely 'LI'. This type is abstract and we will progressively introduce functions to build, combine and run them. The 'LI' type is a pointed functor, but not necessarily a monad nor an applicative functor. Therefore one exports the 'pure' function as 'pureLI'. Building primitives allow to read files or handles: > LI.pureLI :: a -> LI a > LI.hGetContents :: Handle -> LI String > LI.getContents :: LI String > LI.readFile :: FilePath -> LI String > LI.getChanContents :: Chan a -> LI [a] Being a functor is important: it allows to wholly transform the underlying input lazily using standard functions about lists for instance: > length <$> LI.readFile "foo" > words <$> LI.readFile "foo" Extracting a final value of a lazy input ('LI' type) is a matter of using: > LI.run :: (NFData sa) => LI sa -> IO sa Or > LI.run' :: (NFData sa) => LI (SIO a) -> IO sa One can therefore re-write our examples using lazy inputs: > -- embedded printing > countWords = LI.run' (SIO.print . length . words <$> LI.getContents) > -- external printing > maxLineLen = print =<< LI.run (maximum . map length . lines <$> LI.getContents) > lowerText = LI.run' (SIO.putStr . map toLower <$> LI.getContents) == Combining inputs == Finally we come to managing multiple inputs. To get both laziness and precise resource management we will provide dedicated combinators. The first one is as simple as appending. > LI.append :: NFData sa => LI [sa] -> LI [sa] -> LI [sa] This one produces a single stream out that sequences the two given streams. It also sequences the usage of resources: the first resource is closed and then the second one is opened. Note that this combinator is still quite general since one can process each input beforehand: > -- one can drop parts of the inputs > (take 100 <$> i1) `LI.append` (drop 100 <$> i2) > -- one can tag each input to know where they come from > Left <$> i1 `LI.append` Right <$> i2 The second one is 'LI.zipWith' which opens the two resources and joins the items into a single stream. Again, since 'LI' is a functor one can join not only characters but also words, lines, chunks... A problem with zipping is that it stops on the shorter input (loosing a part of the other), hopefully one can prolongate them: > zipMaybesWith :: (NFData sa, NFData sb) -> (Maybe sa -> Maybe sb -> c) -> LI [sa] -> LI [sb] -> LI [c] > zipMaybesWith f xs ys = > map (uncurry f) . takeWhile someJust <$> zip (prolongate <$> xs) (prolongate <$> ys) > where someJust (Nothing, Nothing) = False > someJust _ = True > prolongate :: [a] -> [Maybe a] > prolongate zs = map Just zs ++ repeat Nothing The last one is 'LI.interleave': > LI.interleave :: (NFData sa) -> LI [sa] -> LI [sa] -> LI [sa] This function is currently left biased, moreover each resource is closed as soon as we reach its end. However since the inputs are mixed up together one generally prefers a tagged version trivially build upon this one: > interleaveEither :: (NFData sa, NFData sb) => LI [sa] -> LI [sb] -> LI [Either sa sb] > interleaveEither a b = interleave (map Left <$> a) (map Right <$> b) Here are some final programs that scale well with the number of files. > -- number of words in the given files > main = print =<< LI.run . fmap (length . words) . LI.concat . map LI.readFile =<< getArgs > -- almost the same thing but counts words independently in each file > main = print > =<< LI.run . fmap sum . LI.sequence . map (fmap (length . words) . LI.readFile) > =<< getArgs > -- prints to stdout swap-cased concatenation of all input files > main = LI.run' . (fmap (SIO.putStr . fmap swapCase) . LI.concat . map LI.readFile) =<< getArgs > where swapCase c | isUpper c = toLower c > | otherwise = toUpper c > -- sums character code points of inputs > main = print =<< LI.run . fmap (sum . map (toInteger . ord)) . LI.concat . map LI.readFile =<< getArgs Our solution is from now widely available as an Hackage package named "safe-lazy-io" [4]. We hope you will freely enjoy using Lazy/IO again! As usual, criticisms, comments, and help are expected! Finally, I would like to thank Benoit Montagu and Francois Pottier for helping me out to polish this work! [1]: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/safe-lazy-io [2]: http://okmij.org/ftp/Streams.html [3]: http://www.haskell.org/pipermail/haskell/2009-March/021064.html [4]: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/strict-io -- Nicolas Pouillard

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Haskell Platform: status update and call for volunteers
by Duncan Coutts 31 Mar '09

31 Mar '09

All, We'd like to give you an update on the status of the Haskell Platform. Background ---------- For background on what the Haskell Platform is about see these slides: http://blog.well-typed.com/wp-content/uploads/2008/11/haskell-platform.pdf The wiki page also gives an overview and links to further resources: http://www.haskell.org/haskellwiki/Haskell_Platform Current status -------------- There are no more policy questions to resolve for the first release. It is a matter of getting things done. The first platform release will contain: * ghc-6.10.2 * the "extra libs" (exact list on the issue tracker wiki below) * haddock, happy and alex * the cabal command line tool and it's dependencies. The plan calls for binary installers for Windows and OSX, a generic source tarball for Unix, and native packages for distros. Currently however things are stalled because Don and I have been too busy to put serious time into the task of building installers. It is not fair for our time problems to hold everything up. Call for volunteers ------------------- We are calling for volunteers for an action group. We need volunteers to take charge of various platforms and to manage the overall release. We would like to release a beta at the upcoming Haskell Hackathon in Utrecht (April 17-19). However this will *only* happen if people volunteer to help build distributions for different platforms. In particular we need: * Release manager / coordinator * Website with downloads and release notes * Someone in charge of each platform: * Windows installer * OSX installer * Generic Unix source tarball * Distribution packages: debian, fedora, gentoo, arch, BSD* etc Don and I will be able to help coordinate things and point people in the direction of tasks that need doing. The person in charge of each platform is responsible for building appropriate native packages / installer and coordinating the effort to test that the stuff installs ok and works. If no one volunteers, we simply won't have an Haskell Platform release for that platform. Resources: * Meta-package: darcs get http://code.haskell.org/haskell-platform * Issue tracker: http://trac.haskell.org/haskell-platform/ * Mailing list: http://projects.haskell.org/cgi-bin/mailman/listinfo/haskell-platform Please join the mailing list and volunteer! In the medium term we want to organise things with two overlapping groups. A "doers" group and a "talkers" group. The "doers" group deals with actually building installers and packages and making releases. The "talkers" group is for making decisions (in consultation with the community in general) about which packages go into the platform and what standards to demand of them. We are looking for volunteers for the action group now. As we mentioned, for the first release there is nothing for the talkers to do, though there will be plenty to do for the second major release. Duncan and Don

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Re: [Haskell-cafe] Haskell Weekly News: Issue 111 - March 28, 2009
by Rishiyur Nikhil 30 Mar '09

30 Mar '09

Speaking of lambdas and gotos, some of you may remember the great Professor Eiichi Goto of Japan. You can see an obituary at: http://www.sigsam.org/bulletin/articles/153/goto.pdf He was one of the Japanese pioneers of Lisp, symbolic computing, and architectural support for symbolic computing. He was one of the developers of "hash-consing". He used to joke about his own name, along the lines of: "I'm considered harmful. They're all trying to get rid of me." Nikhil

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ANN: cmonad 0.1.1
by Lennart Augustsson 30 Mar '09

30 Mar '09

I've uploaded my CMonad package to Hackage. It allows you to write Haskell code in a C style. Unfortunately, GHC lacks certain optimizations to make efficient code when using CMonad, so instead of C speed you get low speed. Example: Computing some Fibonacci numbers: fib = do { a <- arrayU[40]; i <- auto 0; a[0] =: 1; a[1] =: 1; for (i =: 2, (i :: EIO Int) < 40, i += 1) $ do { a[i] =: a[i-1] + a[i-2]; }; retrn (a[39]); } Example: Copying stdin to stdout: cat = do { c <- auto 0; while ((c =: getchar()) >= 0) $ do { putchar(c); }; return (); } -- Lennart

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ANNOUNCE: wxAsteroids 1.0
by Henk-Jan van Tuyl 30 Mar '09

30 Mar '09

Your space ship enters an asteroid belt, try to avoid collisions! wxAsteroids is a game demonstrating the wxHaskell GUI. More about this at: http://www.haskell.org/haskellwiki/wxAsteroids -- Met vriendelijke groet, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ --

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Haskell Weekly News: Issue 111 - March 28, 2009
by Brent Yorgey 29 Mar '09

29 Mar '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20090328 Issue 111 - March 28, 2009 --------------------------------------------------------------------------- Welcome to issue 111 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements CHP package. Neil Brown [2]announced the release of version 1.2.0 of the [3]CHP library (which supports explicit message-passing concurrency in Haskell), with various bug-fixes and a new "clock" synchronisation primitive. smartword 0.0.0.5 Web based flash card for Word Smart I and II vocabularies. Ki Yung Ahn [4]announced the release of [5]smartword 0.0.0.5, a web based flash card system for Word Smart I and II, a popular book series for studying GRE vocabularies. HackMail 0.0 -- Procmail + Monads = Awesome!. Joe Fredette [6]announced his very second Hackage upload, [7]HackMail. Hackmail is a Procmail-alike, though it doesn't (yet) support procmail syntax. It dynamically loads a haskell source file and then sits as a daemon watching a directory for new emails. The source file contains a function which sorts email and delivers it to some directory. FallingBlocks 0.1. Ben Sanders [8]announced [9]fallingblocks, a Tetris clone using SDL. io-capture-0.2 capturing std(out|err) in IO action. Yusaku Hashimoto [10]announced the release of [11]io-capture 0.2, a library to capture stdout and stderr in an IO action. It exports a function capture, which takes an IO action and a String representing the entire input, and returns Strings representing the data written to stdout and stderr. wxAsteroids 1.0. Henk-Jan van Tuyl [12]announced [13]wxAsteroids, a game demonstrating the wxHaskell GUI. The votes are in!. Eelco Lempsink [14]announced that the [15]results of the Haskell logo competition are in! Congratulations to Jeff Wheeler on his winning design. Making videos of your project. Don Stewart [16]described how to create short screencasts showing off your latest awesome Haskell project. WinGhci, a GUI for GHCI on Windows. Pepe Gallardo [17]announced the first release of [18]WinGhci, a simple GUI for GHCI on Windows. It is closely based on WinHugs, and provides similar functionality. hranker: Basic utility for ranking a list of items (e.g. for the logo poll). Robin Green [19]announced [20]hranker, a command-line utility that helps the user rank a list of items (of any type implementing Show, Eq and Ord). The hope is that the code is sufficiently clear that it could also serve as an educational piece of code, especially for people wanting to learn how to use the HCL library. salvia-0.1, salvia-extras-0.1. Sebastiaan Visser [21]announced a new version of [22]Salvia, a lightweight Haskell Web Server Framework. Changes in this release include easier dependencies, some new default handler environments that simplify setting up a server application, support for keep-alive, a great deal of additional documentation, support for Windows, and various cleanup and bug fixes. Haddock 2.4.2. David Waern [23]announced a new release of [24]Haddock, the Haskell documentation tool. This is a bug fix release only, and it's the same version that will ship with GHC 6.10.2, unless any important problems are discovered before the GHC release. Because the .haddock file format has changed, links to previously installed documentation will not work when generating documentation using this version. ansi-terminal, ansi-wl-pprint - ANSI terminal support for Haskell. Max Bolingbroke [25]announced the [26]ansi-terminal and [27]ansi-wl-pprint packages, which allow Haskell programs to produce much richer console output by allowing colorisation, emboldening and so on. Both Unix-like (OS X, Linux) and Windows operating systems are supported (via a pure Haskell ANSI emulation layer for Windows). I/O library for Windows. Felix Martini [28]announced the [29]package, an I/O library for Windows using Windows API functions with I/O completion port support. The main goal of this library is to support Simon Marlow's new Handle API once he has added that to GHC. The library also has a compatibility module for socket functions from the network-bytestring package. Discussion Grouping - Map / Reduce. Günther Schmidt [30]asked about a way to lazily group an unordered list of key/value pairs, leading to some interesting solutions and discussion of preserving laziness. about Haskell code written to be "too smart". Manlio Perillo began an [31]epic discussion about Haskell coding style, idioms, pedagogy, and much, much more. Blog noise [32]Haskell news from the [33]blogosphere. * >>> : [34]I18n and Haskell. Internationalization of Haskell programs. * Holumbus: [35]Holumbus-Distribution Update. * Roman Cheplyaka: [36]Recent activity. Ongoing Hpysics development. * Jason Dagit: [37]Type-Correct Changes---A Safe Approach to Version Control Implementation. Jason is now a Master of Computer Science. * Sebastian Fischer: [38]Fair conjunction and disjunction. * Luke Palmer: [39]Certificate Design Pattern. * >>> Daniel Burrows: [40]Sometimes, tools are useful.. * GHC / OpenSPARC Project: [41]Pinning threads to cores. * Galois, Inc: [42]One Million Haskell Downloads.... * Thomas M. DuBuisson: [43]Yet another proposal for Haskell - the ever growing language. * Christopher Lane Hinson: [44]Twilight Hero. * Xmonad: [45]xmonad download statistics. * LHC Team: [46]Ease of implementation.. * Darcs: [47]darcs weekly news #22. * Well-Typed.Com: [48]Regression testing with Hackage. * Neil Mitchell: [49]Concise Generic Queries. * >>> Vo Minh Thu: [50]First stab at Template Haskell. * >>> Nax: [51]HStringTemplate. Quotes of the Week * ddarius: fmap: Because getting functions to the values is half the battle. * monochrom: Monad is about postmodernism. There are laws but no one owns them. You can interpret them any way you want. You can write about your own understanding and the meaning of your writing is not fixed. * conal: Recursion is the goto of functional programming * monochrom: "Monad is about computation." "Our company is about synergy." "iPod is about coolness." Godawful postmodernism nothingness. * olsner: nah, SkyNet is just a zygohistomorphic prepromorphism, nothing fancy * vixey: put some restriction like every token has a neighbourhood locally homeomophic to algol * gwern: Unfortunately Neo, no one can be *told* what the Monad is. About the Haskell Weekly News New editions are posted to [52]the Haskell mailing list as well as to [53]the Haskell Sequence and [54]Planet Haskell. [55]RSS is also available, and headlines appear on [56]haskell.org. To help create new editions of this newsletter, please see the information on [57]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [58]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://blogs.kent.ac.uk/crg-group/2009/03/chp-120-now-with-clocks/ 3. http://www.cs.kent.ac.uk/projects/ofa/chp/ 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55899 5. http://kyagrd.dyndns.org/~kyagrd/project/smartword/ 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55851 7. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HackMail 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55812 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/fallingblocks 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55786 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/io%2Dcapture 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55783 13. http://www.haskell.org/haskellwiki/wxAsteroids 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55500 15. http://www.cs.cornell.edu/w8/~andru/cgi-perl/civs/results.pl?num_winners=1&… 16. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55495 17. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55446 18. http://code.google.com/p/winghci/ 19. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55434 20. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hranker 21. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55424 22. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/salvia 23. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55345 24. http://www.haskell.org/haddock/ 25. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55324 26. http://batterseapower.github.com/ansi-terminal/ 27. http://batterseapower.github.com/ansi-wl-pprint/ 28. http://article.gmane.org/gmane.comp.lang.haskell.cafe/55322 29. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/winio 30. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/55579 31. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/55539 32. http://planet.haskell.org/ 33. http://haskell.org/haskellwiki/Blog_articles 34. http://progandprog.blogspot.com/2009/03/i18n-and-haskell.html 35. http://holumbus.fh-wedel.de/blog/?p=21 36. http://physics-dph.blogspot.com/2009/03/recent-activity.html 37. http://blog.codersbase.com/2009/03/25/type-correct-changes-a-safe-approach-… 38. http://www-ps.informatik.uni-kiel.de/~sebf/projects/fair-predicates.html 39. http://lukepalmer.wordpress.com/2009/03/24/certificate-design-pattern/ 40. http://algebraicthunk.net/~dburrows/blog/entry/sometimes-tools-are-useful/ 41. http://ghcsparc.blogspot.com/2009/03/pinning-threads-to-cores.html 42. http://www.galois.com/blog/2009/03/23/one-million-haskell-downloads/ 43. http://tommd.wordpress.com/2009/03/22/yet-another-proposal-for-haskell-the-… 44. http://blog.downstairspeople.org/2009/03/22/twilight-hero/ 45. http://xmonad.wordpress.com/2009/03/22/xmonad-download-statistics/ 46. http://lhc-compiler.blogspot.com/2009/03/ease-of-implementation.html 47. http://blog.darcs.net/2009/03/darcs-weekly-news-22.html 48. http://blog.well-typed.com/2009/03/regression-testing-with-hackage/ 49. http://neilmitchell.blogspot.com/2009/03/concise-generic-queries.html 50. http://thu.selfip.org/entry/first-stab-th.html 51. http://nax.is-a-geek.net/blog/entries/10/hstringtemplate 52. http://www.haskell.org/mailman/listinfo/haskell 53. http://sequence.complete.org/ 54. http://planet.haskell.org/ 55. http://sequence.complete.org/node/feed 56. http://haskell.org/ 57. http://haskell.org/haskellwiki/HWN 58. http://code.haskell.org/~byorgey/code/hwn/

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[FMICS 2009] Fourth Call for Papers
by FMICS 2009 workshop chair 27 Mar '09

27 Mar '09

FMICS 2009 - 4TH CALL FOR PAPERS Please visit: http://users.dsic.upv.es/workshops/fmics2009 ************************************************************ * 14th International Workshop on * * Formal Methods for Industrial Critical Systems * * FMICS 2009 * * * * November 2-3, 2009 * * Eindhoven, The Netherlands * ************************************************************ * ** NEWS ** * * * * >> Invited speakers confirmed * * Dino Distefano Queen Mary, Univ. London, UK * * Diego Latella ISTI-CNR, Italy * * Thierry Lecomte ClearSy, France * * Ken McMillan Cadence, USA * * * ************************************************************ * * * LNCS proceedings * * Springer has confirmed that the proceedings * * will be published in their Lecture Notes in * * Computer Science series. * * * * Price for best paper -- awarded by EASST * * * ************************************************************ IMPORTANT DATES --------------- Deadline for abstracts: 1st April Deadline for papers: 7 April Accept/Reject notification: 15 June Camera-ready version: 15 July Workshop: 2-3 November SCOPE OF THE WORKSHOP --------------------- The aim of the ERCIM FMICS workshop series is to provide a forum for researchers who are interested in the development and application of formal methods in industry. In particular, these workshops bring together scientists and engineers that are active in the area of formal methods and interested in exchanging their experiences in the industrial usage of these methods. These workshops also strive to promote research and development for the improvement of formal methods and tools for industrial applications. Topics include, but are not restricted to: - Design, specification, code generation and testing based on formal methods. - Methods, techniques and tools to support automated analysis, certification, debugging, learning, optimization and transformation of complex, distributed, real-time systems and embedded systems. - Verification and validation methods that address shortcomings of existing methods with respect to their industrial applicability (e.g., scalability and usability issues). - Tools for the development of formal design descriptions. - Case studies and experience reports on industrial applications of formal methods, focusing on lessons learned or identification of new research directions. - Impact of the adoption of formal methods on the development process and associated costs. - Application of formal methods in standardization and industrial forums. INVITED SPEAKERS ---------------- Dino Distefano Queen Mary, Univ. London, UK Diego Latella ISTI-CNR, Italy Thierry Lecomte ClearSy, France Ken McMillan Cadence, USA CO-CHAIRS --------- Maria Alpuente Tech. University Valencia, Spain Byron Cook Microsoft Research, UK PROGRAM COMMITTEE ------------------- Hassan Ait-Kaci Ilog, Canada Maria Alpuente Tech. University Valencia, Spain Thomas Arts IT-Univ. i Goteborg, Sweden Demis Ballis Universita Udine, Italy Josh Berdine Microsoft Research, UK Lubos Brim Masarykova Univ., Czech Republic Darren Cofer Rockwell Collins, USA Byron Cook Microsoft Research, UK Patrick Cousot Ecole Normale Superieure, France Santiago Escobar Tech. University Valencia, Spain Azadeh Farzan University of Toronto, Canada Hubert Garavel INRIA Rhone-Alpes, France Stefania Gnesi ISTI-CNR, Italy Alexey Gotsman University of Cambridge, UK Holger Hermanns Universitat Saarlandes, Germany Christophe Joubert Tech. University Valencia, Spain Daniel Kroening ETH Zurich, Switzerland Michael Leuschel Universitat Dusseldorf, Germany Pedro Merino Universidad de Malaga, Spain Juan Jose Moreno-Navarro Univ. Politecnica Madrid, Spain Corina Pasareanu NASA Ames Research Center, USA Jaco van de Pol Univ. Twente, The Netherlands Murali Rangarajan Honeywell, USA Jakob Rehof Tech. Univ. Dortmund, Germany Andrey Rybalchenko Max-Planck-Gesellschaft, Germany Marcel Verhoef Chess, The Netherlands Martin Wirsing Universitat Munchen, Germany Hongseok Yang University of London, UK Greta Yorsh IBM Watson Research Center, USA ERCIM FMICS WG COORDINATOR -------------------------- Alessandro Fantechi Univ. Firenze, ISTI-CNR, Italy WORKSHOP CHAIR -------------- Christophe Joubert Tech. University Valencia, Spain PAPER SUBMISSIONS ----------------- Submissions must be made electronically through the EasyChair system. Papers should be up to 16 pages in LNCS format, with the names and affiliations of the authors and a clear and informative abstract. Additional details may be included in a clearly marked appendix, which will be read at the discretion of the program committee. All submissions must report on original research. Submitted papers must not have previously appeared in a journal or conference with published proceedings and must not be concurrently submitted to any other peer-reviewed workshop, symposium, conference or archival journal. Any partial overlap with any such published or concurrently submitted paper must be clearly indicated. Case study papers should identify lessons learned, validate theoretical results (such as scalability of methods), or provide specific motivation for further research and development. The workshop proceedings will be published in the Springer series Lecture Notes in Computer Science (LNCS). CO-LOCATION ----------- FMICS 2009 is part of the first Formal Methods Week (FMweek), which will bring together a choice of events in the area, including TESTCOM/FATES (Conference on Testing of Communicating Systems and Workshop on Formal Approaches to Testing of Software), FACS (Formal Aspects of Component Software), PDMC (Parallel and Distributed Methods of verifiCation), FM2009 (Symposium of Formal Methods Europe), CPA (Communicating Process Architectures), FAST (Formal Aspects of Security and Trust), FMCO (Formal Methods for Components and Objects), and the REFINE Workshop. For the latest information on FMweek, see http://www.win.tue.nl/fmweek. ************************************************************ * * * +============================================+ * * | | * * | ** FMweek ** | * * | | * * +============================================+ * * | CPA | FACS | FAST | * * +--------------------------------------------+ * * | FM2009 | FMCO | FMICS | * * +--------------------------------------------+ * * | PDMC | REFINE | TESTCOM/FATES | * * +--------------------------------------------+ * * | http://www.win.tue.nl/fmweek | * * +============================================+ * * * ************************************************************

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jhc dependencies for ghc-6.10.1
by Philip K.F. Hölzenspies 27 Mar '09

27 Mar '09

Dear John, et al. I will be trying jhc out, because it sounds like a good idea for some of my number-crunching apps. I just wanted to tell you how my build with ghc-6.10.1 (out-of-the-box) went, although it's not completely fair, because I may have some things from hackage installed already. Anyhow, I followed your requirement list (binary,zlib,utf8-string) and ran into the following missing dependencies: readline fgl These were removed from ghc and extralibs, resp. You may want to list these on your installation page for 6.10 builds. Also, people may like to be pointed to this ticket (I ran into this): http://hackage.haskell.org/trac/ghc/ticket/2897 Two more things that struck me: - After the installation of jhc, I just had to try it: took a clean directory fresh from the tarball, did ./configure --with-hc=jhc && make. Unfortunately: /home/holzensp/usr/bin/jhc -I./StringTable -I./cbits -I./cbits -optc-std=c99 -optc-O2 -optc-Wall StringTable/StringTable_cbits.c -c -o StringTable/StringTable_cbits.o Error: Module not found: StringTable/StringTable_cbits.c make[1]: *** [StringTable/StringTable_cbits.o] Error 1 - After the initial installation a directory appeared in my $HOME/usr/share, called jhc-0.5. It seems not all version numbers were bumped ;) Regards, Philip

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