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ANN: hscolour-1.6
by Malcolm Wallace 21 Dec '06

21 Dec '06

hscolour-1.6 ------------ HsColour is a syntax-highlighter for Haskell code. It can generate ANSI terminal colour codes, HTML, and CSS, and can insert hyperlink anchors for function definitions (useful in conjunction with Haddock). HsColour-1.6 is now available. The major addition is a new LaTeX output mode (contributed by Thomas Sutton). Minor fixes include a buffering change to allow you to use HsColour interactively in co-operation with e.g. ghci, on an ANSI terminal. http://www.cs.york.ac.uk/fp/darcs/hscolour Regards, Malcolm

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Haskell Weekly News: December 20, 2006
by dons＠cse.unsw.edu.au 19 Dec '06

19 Dec '06

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20061220 Issue 54 - December 20, 2006 --------------------------------------------------------------------------- Welcome to issue 54 of HWN, a weekly newsletter covering developments in the Haskell community. A new release of the Edison data structures library, along with several other new libraries, and some new Haskell articles in the blogspace. Announcements Edison 1.2.1. Robert Dockins [1]announced the 1.2.1 release of [2]Edison. Edison is a famous library of efficient, purely-functional data structures in Haskell. Notable changes from the previous version include: a new sequence implementation based on finger trees; documentation fixes dealing with the licence; added a few methods to EnumSet for wrapping and unwrapping the underlying Word 1. http://article.gmane.org/gmane.comp.lang.haskell.general/14662 2. http://www.eecs.tufts.edu/~rdocki01/ Basic serialisation library using SYB. Stefan O'Rear [3]announced GenericSerialize, [4]a library for serialization using the existing generic-programming framework. It is often advocated that support for serialization should be added to the compiler (e.g. in the form of a deriving(Binary)). With this project Stefan wants to show that the existing infrastructure is sufficient, and has some advantages over a dedicated serialization interface. GenericSerialize supports multiple serialization modes. 3. http://article.gmane.org/gmane.comp.lang.haskell.general/14656 4. http://members.cox.net/stefanor/genericserialize vty 1.0. Stefan O'Rear [5]announced vty 1.0, a simple [6]terminal interface library. It provides: handling of suspend/resume, window resizes, computation of minimal differences, minimizes repaint area, automatically decodes keyboard keys into (key,modifier) tuples, and more! 5. http://article.gmane.org/gmane.comp.lang.haskell.general/14670 6. http://members.cox.net/stefanor/vty Monad.Reader call for copy. Wouter Swierstra [7]reminded us that its still not too late to write something for the next issue of [8]The Monad.Reader! We have a nice issue slowly shaping up, but your contribution is still very welcome. Get in touch with Wouter if you intend to submit something -- the sooner you let him know what you're up to, the better. 7. http://article.gmane.org/gmane.comp.lang.haskell.general/14638 8. http://www.haskell.org/haskellwiki/TheMonadReader Ranged Sets. Paul Johnson [9]announced that Ranged Sets now have a Monoid instance, and singletons (i.e. a range holding a single value), thanks to Jean-Philippe Bernardy. 9. http://article.gmane.org/gmane.comp.lang.haskell.general/14663 CalDims 1.0 (RC 1). schneegloeckchen [10]announced CalDims, a calculator aware of units. Its available from [11]the Haskell wiki. It includes support for user defined basic units and derrived units; user defined functions; work sheets can be modified/saved via shell; (1/3)*3 == 1 (No rounding errors); built-in feature to simplify units and easy unit-conversion. 10. http://article.gmane.org/gmane.comp.lang.haskell.general/14671 11. http://www.haskell.org/haskellwiki/CalDims JoinCabal. Dougal Stanton [12]announced an alternative to mkcabal, for initialising new cabal projects: [13]JoinCabal, available [14]via darcs. JoinCabal will create stub sources files with a license header, and appropriate license for you code, making it easier to set up a valid cabal build system. 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17600 13. http://brokenhut.no-ip.org/~dougal/cgi-bin/darcsweb.cgi?r=JoinCabal;a=summa… 14. http://brokenhut.no-ip.org/~dougal/darcs/joincabal/ Haskell Vim plugin. Arthur van Leeuwen [15]announced a new [16]vim plugin for Haskell providing some preliminary folding support, easy insertion of type signatures into programs, and support for handling .hi files. 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17675 16. http://www.cs.uu.nl/~arthurvl/haskell.vba Haskell' This section covers the [17]Haskell' standardisation process. * [18]Strictly matching monadic let and overloaded Bool 17. http://hackage.haskell.org/trac/haskell-prime 18. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1956/focus=1974 Discussion Automonadization of code. Adam Megacz [19]asked if there any work on automatic translation of code in some tiny imperative language into Haskell code that uses the ST and/or IO monads (or perhaps even pure functional code)? 19. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17326/focus=17326 What are the points in pointfree style?. Steve Downey [20]wondered about the origin of the term 'points' in pointfree style. 20. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17560/focus=17560 Rebinding >>= for restricted monads. David Roundy [21]pondered rebinding the >>= syntax in order to provide a more restricted monad. 21. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17646/focus=17646 #haskell reaches 300 users. Don Stewart [22]noticed that the [23]#haskell IRC channel has now reached the 300 user mark, making it one of the top 15 channels on the freenode network. 22. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17705/focus=17705 23. http://haskell.org/haskellwiki/IRC_channel Blog noise [24]Haskell news from the blogosphere. * [25]Do-notation considered harmful * [26]Reddit discussion considered productive * [27]The Dot-Matrix Printhead: a Haskell Toy * [28]The Revised Dot-Matrix Printhead * [29]The monad laws * [30]On documentation * [31]Software requirements do not change * [32]Haskell and the web: some ideas in progress * [33]Using Haskell in Python: haskellembed * [34]Literate programming * [35]The lambda revolution, Episode V, the deb strikes back * [36]On syntax * [37]Syntax: adding Lisp macros * [38]More on syntax * [39]UCBLogo and the Fibonacci sequence * [40]Linguistic comparisons: string reversal * [41]New Software Technology: Blockage On Line * [42]More silver bullets * [43]Preventing NullPointerExceptions, Maybe * [44]Adventures in Haskell: the Parsec magic weapon * [45]Advertising Haskell * [46]Programming Haskell: part 1 * [47]Programming Haskell: part 2 * [48]Programming Haskell: part 3 * [49]Introductory Haskell Programming in the UNIX Environment * [50]On Haskell, Intuition And Expressive Power * [51]Your order is ready sir * [52]It's alive (the French Haskell community) * [53]Maybe monad in Java * [54]Secret Santas in Haskell I: Preliminaries * [55]Secret Santas in Haskell II: Orbits and Lists * [56]Why Closures in Dolphin is a Good Idea * [57]Haskell Stacks : Two Different Ways * [58]Haskell Golf Scores * [59]Languages * [60]Questions on Haskell Style (and Polynomials redux) * [61]A simple RSS aggregator in 50 lines of Haskell using HXT 24. http://planet.haskell.org/ 25. http://syntaxfree.wordpress.com/2006/12/12/do-notation-considered-harmful/ 26. http://syntaxfree.wordpress.com/2006/12/13/reddit-discussion-considered-pro… 27. http://praisecurseandrecurse.blogspot.com/2006/12/dot-matrix-printhead-hask… 28. http://praisecurseandrecurse.blogspot.com/2006/12/revised-dot-matrix-printh… 29. http://cale.yi.org/index.php/The_Monad_Laws 30. http://blog.milkfarmsoft.com/?p=29 31. http://blog.tmorris.net/software-requirements-do-not-change/ 32. http://haskell-web.blogspot.com/2006/12/some-ideas-in-progress_13.html 33. http://www.kuarepoti-dju.net/index.php?p=86 34. http://benjisimon.blogspot.com/2006/12/programs-as-stories.html 35. http://pupeno.com/blog/the-lambda-revolution-episode-v-the-deb-strikes-back 36. http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/14#on-syntax 37. http://nominolo.blogspot.com/2006/12/syntax.html 38. http://www.cse.unsw.edu.au/~dons/blog/2006/12/15#on-syntax-again 39. http://sob.apotheon.org/?p=171 40. http://sob.apotheon.org/?p=170 41. http://cogito.blogthing.com/2006/12/14/new-software-technology-blockage-on-… 42. http://clabs.org/blogki/blogki.cgi?page=/ComputersAndTechnology/AndTheNomin… 43. http://rickyclarkson.blogspot.com/2006/09/using-strong-typing-to-eliminate.… 44. http://jpmoresmau.blogspot.com/2006/12/adventures-in-haskell-parsec-magic.h… 45. http://neilmitchell.blogspot.com/2006/12/advertising-haskell.html 46. http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/16#programming-haskell-intro 47. http://www.cse.unsw.edu.au/~dons/blog/2006/12/17#programming-haskell-part-2 48. http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/18#ph-3 49. http://blog.kfish.org/software/haskell/intro-haskell-unix.html 50. http://www.defmacro.org/ramblings/haskell-productivity.html 51. http://lambda-the-ultimate.org/node/1905#comment-23273 52. http://koweycode.blogspot.com/2006/12/its-alive.html 53. http://blog.tmorris.net/maybe-monad-in-java/ 54. http://mult.ifario.us/articles/2006/12/18/secret-santas-in-haskell-i-prelim… 55. http://mult.ifario.us/articles/2006/12/18/secret-santas-in-haskell-ii-orbit… 56. http://rickyclarkson.blogspot.com/2006/12/why-closures-in-dolphin-is-good-i… 57. http://progexpr.blogspot.com/2006/11/haskell-stacks-two-different-ways.html 58. http://progexpr.blogspot.com/2006/11/haskell-golf-scores.html 59. http://computativestylings.blogspot.com/2006/12/languages.html 60. http://sambangu.blogspot.com/2006/12/questions-on-haskell-style-and 61. http://cale.yi.org/index.php/HRSS Quotes of the Week * Cale: I spent a whole summer being paid to write a nondeterministic search program in the list monad * monochrom: 007 titles for Haskellers: fromForeignPtr withCString; You Only lift Twice; Bottoms Are Forever; The Monad with the Pure Function; For Your Types Only; A view to A seq; Licence to killThread; iterate Never Dies; unsafePerformIO Is Not Enough. * DavidRoundy: ... fun of haskell-cafe is that it's where all the cool people hang out * dons: Coding drunk in Haskell is ok though, its like drinking on a passenger plane flight -- the stewards will prevent you from hurting anyone. However, coding drunk in C is just scary, DUI territory, and should not be allowed. * JulianMorrison: Small startup companies are the expendable sensory and feeding apparatus of the mainstream. * droundy: With a higher-kinded monad and phantom existential witness types, darcs would be very fun... * dons: The alien rulers of the galaxy must surely use a statically typed language with type inference * dibblego: Java programmers prefer referential transparency too, they just call it 'design patterns' or something * tessier: After the last newbies head exploded trying to read everything on that monad link there was a lot of paperwork. We'd like to avoid doing that again. Code Watch Fri Dec 8 21:03:34 PST 2006. Andy Gill. [62]Adding tracing support (HPC) 62. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/18263 Wed Dec 13 08:45:38 PST 2006. simonpj. [63]You can now have an MVar with a polymorphic contents 63. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/18279 About the Haskell Weekly News Each week, new editions are posted to [64]the Haskell mailing list as well as to [65]the Haskell Sequence and [66]Planet Haskell. [67]RSS is also available, and headlines appear on [68]haskell.org. Headlines are available as [69]PDF. The Haskell Weekly News is also [70]available in Spanish translation. To help create new editions of this newsletter, please see the [71]contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get [72]http://www.cse.unsw.edu.au/~dons/code/hwn 64. http://www.haskell.org/mailman/listinfo/haskell 65. http://sequence.complete.org/ 66. http://planet.haskell.org/ 67. http://sequence.complete.org/node/feed 68. http://haskell.org/ 69. http://www.cse.unsw.edu.au/~dons/code/hwn/archives/20061220.pdf 70. http://haskell.org/haskellwiki/HWN/es 71. http://haskell.org/haskellwiki/HWN 72. http://www.cse.unsw.edu.au/~dons/code/hwn

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Announce: CalDims 1.0 (RC 1) - A calculator aware of units
by mm 19 Dec '06

19 Dec '06

Hello, i'd like to inform you about the first announced version of CalDims. Its website is in the haskellwiki: http://www.haskell.org/haskellwiki/CalDims CalDims is a calculation tool with the following features: * Support for user defined basic units and derrived units * user defined functions * work sheets can be modified/saved via shell * (1/3)*3 == 1 (No rounding errors) * built-in feature to simplify units * easy unit-conversion Useful hints: * to compile just type `make` and then (optionally) 'make install' as superuser. * to read documentation, start the program and then enter `\?` Future: Short term goal is to provide a stable release so please report all bugs and quirks. For the next major release I am planning to write a worksheet GUI for CalDims + support more datatypes. Here's an example session: /home/schneegloeckchen# caldims CalDims 1.0-rc1 Version: GPL 2 (see the LICENSE file) Type in `\?' to read the inline help. > # A 60 Watt electric light is burning 2 hours a day. How much energy is consumed in one week? > 60 W * 2 h / d * 7 d 3024000.0 J > # What's that in Watt hours? > 60 W * 2 h / d * 7 d | W h 840.0 W h > #How much kWh is it in a year (we derrive `year` and `kW` first) > year := 365 d New unit year:d ok. > kW := 1000 W New unit kW:W ok. > 60 W * 2 h / d * 1 year | kW h 43.8 h kW > #Define new basic dimension for currency + variable for energy price > \u USD Added basic unit `USD'. > energy_price = 0.2 USD / kW / h New function energy_price:USD / kW / h ok. > 43.8 kW h * energy_price 8.76 USD > #A simple function for energy costs > energy_costs (t : s, e:W) = t*e*energy_price New function energy_costs:USD W s / kW / h ok. > energy_costs (20 min, 60 kW) 4.0 USD > #Save everything (units, functions) to a file > \s my_calculation.cal schneegloeckchen

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ANN: vty 1.0: simple terminal interface library
by Stefan O'Rear 18 Dec '06

18 Dec '06

Announcing vty, a very simple terminal interface library. In <150 non-blank non-comment lines of Haskell (and 7 lines of C) vty provides: * Automatic handling of suspend/resume (SIGTSTP+SIGCONT) * Automatic handling of window resizes * Automatic computation of minimal differences * Minimizes repaint area, thus virtually eliminating the flicker problem that plagues ncurses programs * Automatically decodes keyboard keys into (key,[modifier]) tuples * Automatically supports refresh on Ctrl-L. * Automatically supports timeout after 50ms for lone ESC (a barely noticable delay) * Interface is designed for relatively easy compatible extension. Current disadvantages: * No current support for non-ANSI terminals. * Minimal support for special keys on terminals other than the linux-console. (F1-5 and arrow keys should work, but anything shifted isn't likely to.) * Uses the TIOCGWINSZ ioctl to find the current window size, which appears to be limited to Linux and *BSD. darcs get --tag=rel-1.0 http://members.cox.net/stefanor/vty http://members.cox.net/stefanor/vty/dist/vty-1.0.tar.gz To compile the demonstration program: ghc --make Test.hs gwinsz.c

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ANNOUNCE: Visual Haskell 0.2 final
by Krasimir Angelov 18 Dec '06

18 Dec '06

Hello Haskellers, The final version of Visual Haskell 0.2 is ready: http://www.haskell.org/visualhaskell This is the first version that is: - available for both VStudio 2003 and VStudio 2005 - distributed with a stable GHC version (6.6) - the plugin itself is much more stable than its first 0.0 version There were important changes after the prerelease version so it is recommended to upgrade you installation. Many thanks to Simon Marlow, Brian Smith, Wayne Vucenic, Jared Updike and Pepe Iborra that helped me with the preparation of this new release. Cheers, Krasimir

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Simple variable-state `monad'
by oleg＠pobox.com 17 Dec '06

17 Dec '06

The familiar State monad lets us represent computation with a state that can be queried and updated during the computation. The state must have the same type during the entire computation however. One sometimes wants to express a computation where not only the value but the type of the state can be updated as well -- while maintaining static typing. David Roundy has recently suggested a similar `restricted monad' > class WitnessMonad wm where > (>>=) :: wm w w' a -> (a -> wm w' w'' b) -> wm w w'' b > (>>) :: wm w w' a -> wm w' w'' b -> wm w w'' b > return :: a -> wm w w' a > fail :: String -> wm w w' a > > which obviously just adds a couple of phantom types indicating the monad > state prior to and after each operation. I actually rather like this > redefined monad, as it seems like it'd be useful in lots of places (e.g. a > restricted IO monad that disallows use of a file handle after it's > closed). To nitpick, such a `restricted monad' no longer can be called `monad' because the type of the bind operation does not satisfy the signature m a -> (a -> m b) -> m b. Proper naming is important so we can understand what kind of animal we're dealing with and so can chose the right way to domesticate it. The problem indeed shows up in many contexts, like ensuring that a file cannot be used after it is closed, or that the lock is properly released. The most common solution to these problems (expressing control-flow proiperties) involves using monad in a contra-variant position. One recent example http://pobox.com/~oleg/ftp/Haskell/yield.hs is ensuring a locking property (a lock can be unlocked only when it is held; one can acquire the same lock several times but must release that many times; no `yield' may be invoked while holding a lock). However, this style is a bit ugly. One wonders if a more direct expression of this `variable style monad' is possible. It seems it is, as the following code demonstrates. It runs with GHC 6.4 and Hugs. {-# OPTIONS -fglasgow-exts #-} -- Variable state monad module EM1 where import Control.Monad.State class Monadish m where gret :: a -> m p p a gbind :: m p q a -> (a -> m q r b) -> m p r b -- Inject regular monads to be monadish things too newtype MW m p q a = MW{ unMW:: m a } instance Monad m => Monadish (MW m) where gret = MW . return gbind (MW m) f = MW (m >>= unMW . f) -- As a warm-up, we write the regular State computation, with the same -- type of state throughout -- First, use the regular Monad.State test1 = runState c (0::Int) where c = do v <- get put (succ v) return v -- (0,1) -- Now, wrap in MW test2 = runState (unMW c) (0::Int) where c = gget `gbind` ( \v -> gput (succ v) `gbind` ( \_ -> gret v)) gget :: (MonadState s m) => MW m s s s gget = MW get gput :: (MonadState s m) => s -> MW m s s () gput = MW . put -- (0,1) -- Introduce the variable-type state newtype VST m si so v = VST{runVST:: si -> m (so,v)} instance Monad m => Monadish (VST m) where gret x = VST (\si -> return (si,x)) gbind (VST m) f = VST (\si -> m si >>= (\ (sm,x) -> runVST (f x) sm)) vsget :: Monad m => VST m si si si vsget = VST (\si -> return (si,si)) vsput :: Monad m => so -> VST m si so () vsput x = VST (\si -> return (x,())) -- Repeat test2 via VST: the type of the state is the same test3 = runVST c (0::Int) >>= print where c = vsget `gbind` ( \v -> vsput (succ v) `gbind` ( \_ -> gret v)) -- (1,0) -- Now, we vary the type of the state, from Int to a Char test4 = runVST c (0::Int) >>= print where c = vsget `gbind` ( \v -> vsput ((toEnum (65+v))::Char) `gbind` ( \_ -> vsget `gbind` ( \v' -> gret (v,v')))) -- ('A',(0,'A')) {- -- The following is an error: Couldn't match `Char' against `Int' Expected type: VST m Char r b Inferred type: VST m Int Int Bool test4' = runVST c (0::Int) >>= print where c = vsget `gbind` ( \v -> vsput ((toEnum (65+v))::Char) `gbind` ( \_ -> vsget `gbind` ( \v' -> gret (v==v')))) -} -- Try polymorphic recursion, over the state. -- crec1 invokes itself, and changes the type of the state from -- some si to Bool. crec1 :: (Enum si, Monad m) => VST m si si Int crec1 = vsget `gbind` (\s1 -> case fromEnum s1 of 0 -> gret 0 1 -> vsput (pred s1) `gbind` (\_ -> gret 1) _ -> vsput True `gbind` (\_ -> crec1 `gbind` (\v -> (vsput s1 `gbind` -- restore state type to si (\_ -> gret (v + 10)))))) test5 = runVST crec1 'a' >>= print -- ('a',11)

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PhD Position, the University of Nottingham
by Henrik Nilsson 17 Dec '06

17 Dec '06

Postgraduate Research in Functional Hybrid Modelling School of Computer Science and IT University of Nottingham The University of Nottingham has an open position for a PhD student to work on EPSRC-funded project called Functional Hybrid Modelling, running for three years. This is a project at the intersection of, on the one hand, programming language semantics, design, and implementation, and, on the other, hybrid modelling and simulation. The ideal applicant would have a first- or upper-second class honours degree or equivalent in Computer Science (or possibly other area of direct relevance to the project), along with expertise in one or more of the following: * functional programming; * semantics, design, and implementation of (declarative) languages; * techniques for (hybrid) modelling and simulation, and related fields of mathematics (numerical methods, numerical analysis, calculus, linear algebra); * modelling and simulation of physical systems. The position is open to UK and EU applicants, but particularly strong applicants from outside the EU may also be considered, subject to the possibilities of securing additional funding. The successful applicant will work within the Foundations of Programming group at the School of Computer Science and IT: http://www.cs.nott.ac.uk/Research/fop/ The group currently comprise 7 academic staff, 5 research staff, and 14 research students. The research areas of the group include Algebra of Programming, Functional Programming (theory and practice), and Logic in Computer Science. The group is a founder member of the Midlands Graduate School in the Foundations of Computer Science, which provides postgraduate courses for PhD students in theoretical computer science. For further information on the studentship and the project, please contact Henrik Nilsson: nhn(a)cs.nott.ac.uk http://www.cs.nott.ac.uk/~nhn -- Henrik Nilsson School of Computer Science and Information Technology The University of Nottingham nhn(a)cs.nott.ac.uk 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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An haskell-fr community ?!
by Olivier Thauvin 17 Dec '06

17 Dec '06

Hi, I just setup a web site, a mailing list and an irc channel on freenode as it seems few people were interested (like me) by an haskell-fr community. Honnestly, I am not sure this website will have a big success, but trying is often better than nothing. I am myself an haskell beginner, but I hope I'll use haskell soon so easilly than I use perl, and so providing many contributions and modules. Any comments and contributions are of course welcome ! OOpppps, the url: http://haskell-fr.zarb.org/ Regards.

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Ranged Sets 0.0.4
by Paul Johnson 17 Dec '06

17 Dec '06

Ranged Sets now have a Monoid instance, and singletons (i.e. a range holding a single value). Thanks to Jean-Philippe Bernardy for the patch. Paul.

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[ANN] Edison 1.2.1
by Robert Dockins 16 Dec '06

16 Dec '06

Fellow Haskellers, I am pleased to announce the 1.2.1 release of Edison. Edison is a library of efficient, purely-functional data structures in Haskell. Notable changes from version 1.2.0.1: * A new sequence implementation based on finger trees (similar to Data.Sequence in the base libs). * Documenation fixes dealing with the licence (the docs previously and incorrectly claimed Edison was under the BSD licence, when it is in fact the MIT license). * Added a few methods to EnumSet for wrapping and unwrapping the underlying Word The project home page is: http://www.eecs.tufts.edu/~rdocki01/ edison.html From here you can find source tarballs, online Haddock docs and the darcs repository. Rob Dockins Speak softly and drive a Sherman tank. Laugh hard; it's a long way to the bank. -- TMBG

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