January 2007 - Haskell-Cafe

Beta Gtk2Hs Getting Started
by Hans van Thiel 09 Jan '07

09 Jan '07

Hello All, The beta of the 'Gtk2Hs:Getting Started' short tutorial for beginners, Haskell GUI for Dummies, if you like :-) can be viewed at http://j-van-thiel.speedlinq.nl/gtk2hs/gtk2hsGetStart.html It tells what Gtk2Hs is, shows how to write and run 'Hello World', introduces the api and explains how to use it, refers to the Glade tutorials, gives an example of widget layout, and ends with some general pointers. It should take no more than 2,3 hours of the user's time. All feedback very welcome. Regards, Hans van Thiel

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Haskell Weekly News: January 09, 2007
by dons＠cse.unsw.edu.au 08 Jan '07

08 Jan '07

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20070109 Issue 56 - January 09, 2007 --------------------------------------------------------------------------- Welcome to issue 56 of HWN, a weekly newsletter covering developments in the [1]Haskell community. More libraries and applications for the new year, and the Haskell Hackathon gets underway! 1. http://haskell.org/ Announcements Happy: LALR(1) parser generator. Simon Marlow [2]announced version 1.16 of [3]Happy, the parser generator system for Haskell. Changes from version 1.15 to 1.16 include switching to Cabal, a new %error directive, new production forms, and attribute grammar support. Happy version 1.16 is required for building GHC version 6.6 and later. 2. http://article.gmane.org/gmane.comp.lang.haskell.general/14726 3. http://www.haskell.org/happy/ Alex: lexical analyser generator. Simon Marlow [4]announced version 2.1.0 of [5]Alex. Changes in Alex 2.1.0 vs. 2.0.1 include switching to Cabal, and slight changes to the error semantics. 4. http://article.gmane.org/gmane.comp.lang.haskell.general/14728 5. http://www.haskell.org/alex/ rdtsc: reading IA-32 time register. Martin Grabmueller [6]announced version 1.0 of [7]package rdtsc has just been released. This small package contains one module called [8]'Rdtsc.Rdtsc', providing the function 'rdtsc' for accessing the 'rdtsc' machine register on modern IA-32 processors. This is a 64-bit counter which counts the number of processor cycles since the machine has been powered up. Using this instruction, you can make very precise time measurements which are independent of the actual CPU frequency. 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/18095/ 7. http://uebb.cs.tu-berlin.de/~magr/projects/rdtsc/ 8. http://uebb.cs.tu-berlin.de/~magr/darcs/rdtsc/ monadLib 3.0. Iavor Diatchki [9]announced a new version of [10]monadLib, a collection of standard monad implementations. Some of the changes compared to the previous version: the whole library is in a single module MonadLib.hs (~500 lines); simpler and more symmetric API; removed the (generic) monadic combinators; removed the search transformer; rewrote some transformers in the 'traditional' way (exceptions and output); there is an optional module that defines base monads corresponding to each transformer. 9. http://article.gmane.org/gmane.comp.lang.haskell.general/14714 10. http://www.csee.ogi.edu/~diatchki/monadLib Shellac 0.6. Robert Dockins [11]announced a simultaneously release of the following related packages: Shellac 0.6 Shellac-readline 0.3 and Shellac-vty 0.1. [12]Shellac is a framework for building read-eval-print style shells which uses configurable backend plugins. The major new feature of this release is the new Shellac-vty backend package, which uses the [13]new Vty library terminal I/O directly. It currently has basic line editing keybindings, paging, and a command history. The main package and Shellac-readline updates consist of minor API updates. 11. http://article.gmane.org/gmane.comp.lang.haskell.general/14715 12. http://www.eecs.tufts.edu/~rdocki01/shellac.html 13. http://members.cox.net/stefanor/vty/ IntelliJIDEA for Haskell. Tony Morris [14]announced syntax highlighting support for [15]Haskell in IntellijIDEA, released under a BSD licence. 14. http://article.gmane.org/gmane.comp.lang.haskell.general/14719 15. http://www.workingmouse.com/research/IntelliJIdea%2DHaskell/ Yampa + GADT for GHC 6.6. Joel Reymont [16]announced a cabalized [17]version of Yampa + GADT for GHC 6.6. Joel also sought comments on cabalisation, testing and example for this package. 16. http://article.gmane.org/gmane.comp.lang.haskell.cafe/18215 17. http://wagerlabs.com/yampa HNOP. Ashley Yakeley [18]updated the status of [19]HNOP, the Haskell library for doing nothing. It has recently been split into two Cabal packages: 'nop', a library of no-op services, and 'hnop', a program that uses nop to do nothing. Both packages can be found in darcs. The two packages are intended to be templates for Cabal projects, so I'm interested in making them as canonical and 'best practices' for packaging libraries and executables. 18. http://article.gmane.org/gmane.comp.lang.haskell.general/14720 19. http://semantic.org/hnop/ Haskell' This section covers the [20]Haskell' standardisation process. * [21]Rough draft of informal pattern-guard (qualifiers) explanations 20. http://hackage.haskell.org/trac/haskell-prime 21. http://article.gmane.org/gmane.comp.lang.haskell.prime/1982 Discussion instance Monad Set, using GADTs. Roberto Zunino [22]announced a definition of the Set datatype, with the usual operations, such that it can be made a member of the Monad class. 22. http://article.gmane.org/gmane.comp.lang.haskell.cafe/18118 GADTs are expressive. Jim Apple [23]described a data type which holds only those terms of the untyped lambda calculus that are reducible to normal form, using GADTs 23. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/18210/focus=18210 Hackage interface. Ross Paterson [24]set up (temporarily) a simple first cut at an [25]interface to the Hackage package database. On a related note, there was some [26]discussion for home pages for Hackage projects, and collecting statistics. 24. http://article.gmane.org/gmane.comp.lang.haskell.libraries/6025 25. http://ross-paterson.dyndns.org/~ross/hackage/ 26. http://article.gmane.org/gmane.comp.lang.haskell.libraries/6035 Conference roundup The Haskell Hackathon. Hac 2007 [27]is being held this week, January 10-12th, in Oxford, with around 20 Haskell coders from across the world gathering to hack on libraries and practical tools for Haskell. Work is planned for at least hackage, Cabal, bytestrings, binary IO, http, GHC, YHC, Hoogle, DrHaskell, WinHugs, GHCi debugger, crypto, QuickCheck 2, Haddock and more besides. Notably, some graduates from this year's Google Summer of Code projects will be attending, with plans to integrate their work into the main project branches. Happy hacking everyone! 27. http://haskell.org/haskellwiki/Hac_2007 Blog noise [28]Haskell news from the blogosphere. * [29]Liberating Myself from the von Neumann Style * [30]First impressions of Haskell: Whoa! * [31]Comparing Gzip Code Reduction * [32]Simple demonstration of Haskell FFI * [33]Does Functional Programming Matter? * [34]2006 in review * [35]Haskell script to replace tabs * [36]Functional programming is functional * [37]The shock of the forgotten * [38]Category theory * [39]Does Haskell need macros? * [40]On darcs * [41]Learning things * [42]Folds for imperative programmers * [43]Dammit all! I've been blubbed * [44]Getting started with installing third-party Haskell packages * [45]A Nice Way to Learn FP * [46]Learning Haskell * [47]Haskell and Eclipse * [48]Haskell and Eclipse: building a server executable * [49]What makes a programming language more productive? * [50]Composability and Productivity * [51]Arithmetic coding in Haskell * [52]A quick and dirty theorem prover in Haskell * [53]Haskell is Fun! * [54]2007, the year of software reliability? * [55]Haskell, bondage-and-discipline and separation-of-concerns programming * [56]Type systems as safety belts * [57]It's Haskell! * [58]Two promising Haskell projects: Vital and Pivot * [59]Exceptions and interrupts 28. http://planet.haskell.org/ 29. http://blogs.nubgames.com/code/?p=4 30. http://blogs.nubgames.com/code/?p=15 31. http://blogs.nubgames.com/code/?p=16 32. http://blog.acolyte.co.za/articles/2007/01/01/simple-demonstration-of-haske… 33. http://denkspuren.blogspot.com/2007/01/does-functional-programming-matter.h… 34. http://koweynlg.blogspot.com/2006/12/state-of-thesis-2006-12-31.html 35. http://chill-yo.blogspot.com/2007/01/haskell-code-replace-tabs.html 36. http://gearon.blogspot.com/2006/10/functional-programming-is-functional.html 37. http://www.serpentine.com/blog/2007/01/01/the-shock-of-the-forgotten/ 38. http://comblog.net/hnbeck/archive/2007/01/05/2384.aspx 39. http://neilmitchell.blogspot.com/2007/01/does-haskell-need-macros.html 40. http://simulacra.in/2007/01/darcs/ 41. http://koweynlg.blogspot.com/2007/01/zommmmbieeee.html 42. http://blog.tmorris.net/folds-for-imperative-programmers/ 43. http://withoutane.com/rants/2007/01/damn-you-haskell 44. http://www.serpentine.com/blog/2007/01/05/getting-started-with-installing-t… 45. http://monadnation.blogspot.com/2007/01/nice-way-to-learn-fp.html 46. http://www.timeblog.net/2007/01/06/haskell/ 47. http://cohatoe.blogspot.com/2006/12/simple-example-walkthrough-ii.html 48. http://cohatoe.blogspot.com/2007/01/building-server-executable.html 49. http://kawagner.blogspot.com/2007/01/what-makes-programming-language-more.h… 50. http://cogito.blogthing.com/2007/01/07/composablility-and-productivity/ 51. http://vandreev.wordpress.com/2007/01/07/arithmetic-coding/ 52. http://vandreev.wordpress.com/2006/12/24/quick-and-dirty-theorem-prover/ 53. http://onthebalcony.wordpress.com/2007/01/08/haskell-is-fun/ 54. http://jguk.org/2007/01/2007-year-of-software-reliability.html 55. http://syntaxfree.wordpress.com/2007/01/08/haskell-bondage-and-discipline-a… 56. http://programming.reddit.com/info/xbc7/comments/cxfs0 57. http://e-scribe.com/news/322 58. http://factor-language.blogspot.com/2007/01/two-promising-haskell-projects.… 59. http://www.weaselhat.com/2007/01/08/exceptions-and-interrupts/ Quotes of the Week * Eric: The Haskell [code] contains no redundancy. In fact, in all the [Haskell] code I've written, in both production and play, each idea is expressed once and only once. It is the Zen ideal of perfect code. And thats never happened to me before. * nostrademons: Haskell is in a similar position [to Scala] - a complex language with many sustaining innovations - but it has one major disruptive innovation. Purity. Now, the question is whether that can be leveraged in a way that makes it useful in some market that existing imperative languages can't reach. My bets are on concurrency... * Excedrin: Isn't OO deprecated? * dpiponi: [monochrom] Nevermind monads. Use arrows. Come join the Dart Side! [dpiponi] Never mind arrows. Use comonads. Cojoin the other side. * nilsi: #haskell is better than Google * sigfpe: I think Haskell is a great language for short attention spans. You can get so much done in one line before you get bored. * timthelion: Oh wait, I LOVE foldr!! And I have only been learning Haskell for hours * kowey: All the things with guards are just there to siphon off the weirdos * Eric: [Haskell] astonishes me at every turn with its beauty and elegance. I've never felt such power. Haskell has brought back a joy in programming that I didnt even know I was missing. * Paul Johnson: Mutable state is actually another form of manual memory management: every time you over-write a value you are making a decision that the old value is now garbage, regardless of what other part of the program might have been using it. About the Haskell Weekly News Each week, new editions are posted to [60]the Haskell mailing list as well as to [61]the Haskell Sequence and [62]Planet Haskell. [63]RSS is also available, and headlines appear on [64]haskell.org. Headlines are available as [65]PDF. To help create new editions of this newsletter, please see the [66]contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get [67]http://www.cse.unsw.edu.au/~dons/code/hwn 60. http://www.haskell.org/mailman/listinfo/haskell 61. http://sequence.complete.org/ 62. http://planet.haskell.org/ 63. http://sequence.complete.org/node/feed 64. http://haskell.org/ 65. http://www.cse.unsw.edu.au/~dons/code/hwn/archives/20070109.pdf 66. http://haskell.org/haskellwiki/HWN 67. http://www.cse.unsw.edu.au/~dons/code/hwn

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why can't you surround (+) in backticks and have it be infix?
by tpledger＠ihug.co.nz 08 Jan '07

08 Jan '07

David House wrote: : | You can fake this: | | (-!) = ($) | (!-) = flip ($) | | foo -! liftM2 (,) !- bar | | Not perfect, but it's interesting nonetheless. | | And yes, this was a product of some #haskell | brainstorming and algorithm tennis. :) :-) Was anyone in that brainstorm thinking of Chung-chieh Shan's -: and :- (http://www.haskell.org/pipermail/haskell-cafe/2002-July/003215.html) or was the similarity just a really cool coincidence? Regards, Tom

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trivial function application question
by brad clawsie 08 Jan '07

08 Jan '07

greetings to this helpful and informative list i have a small problem that will be certainly trivial for almost everyone reading this, i would appreciate a little help lets say i have a string s = "abcdefg" now i have two lists of strings, one a list of patterns to match, and a list of replacement strings: patterns = ["a","b"] replace = ["Z","Y"] from which my intent is that "a" be replaced by "Z", "b" by "Y" etc now using the replace function from MissingH.Str (which i know is now renamed), i wish to apply replace to s using (pattern[0], replace[0]), (pattern[1], replace[1])...(pattern[N], replace[N]). i am sure there is an elegant way to apply replace to s for all of these argument pairs without composing replace N times myself, but the solution escapes me. thanks in advance for any help you can provide for this trivial issue brad

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why can't you surround (+) in backticks and have it be infix?
by tphyahoo 08 Jan '07

08 Jan '07

"Issues: In Haskell, any function or constructor can be enclosed in backticks and then used as an infix operator. " from http://www-users.cs.york.ac.uk/~mfn/hacle/issues/node2.html But this seems to be contradicted by... from #haskell -- 09:19 < tphyahoo> > let func = (+) in 1 `func` 2 -- 09:19 < lambdabot> 3 -- 09:20 < tphyahoo> but ...... -- 09:20 < tphyahoo> 1 `(+)` 2 -- 09:20 < tphyahoo> > 1 `(+)` 2 -- 09:20 < lambdabot> Parse error (+) is a function, is it not? Where's the rub? thomas. -- View this message in context: http://www.nabble.com/why-can%27t-you-surround-%28%2B%29-in-backticks-and-h… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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hsffig build problem
by Jeff Polakow 08 Jan '07

08 Jan '07

Hello, I am trying to install hsffig and I get the following error: bash$ make : : Linking cabal-setup.exe ... Distribution/Simple/Configure.o:fake:(.text+0x74fd): undefined reference to `SHGetFolderPath@20' collect2: ld returned 1 exit status make: *** [cabal-setup] Error 1 I am using ghc6.6 in cygwin on windows XP. Has anyone else encountered and/or overcome this? thanks, Jeff --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

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Re: [Haskell-cafe] no end to the build errors! (wxhaskell, afrp)
by Yang 07 Jan '07

07 Jan '07

thanks, now wxhaskell is installed. (i recommend adding this detail to the docs - i didn't see the message at the end of the make job at all because of the tools i use to automate this process.) now the error i get from wxfruit is: $ ghc --make WXFruit.hs [1 of 1] Compiling WXFruit ( WXFruit.hs, WXFruit.o ) WXFruit.hs:81:31: parse error on input `->' On 1/7/07, Brandon S. Allbery KF8NH allbery-at-ece.cmu.edu |haskell-cafe| <...> wrote: > > On Jan 7, 2007, at 20:54 , Yang wrote: > > > WXFruit.hs:12:17: > > Could not find module `Graphics.UI.WX': > > Hm. Did you install the whole thing? You need to do "make; make > install; make wx; make wx-install" to get all of it --- and > Graphics.UI.WX is in the latter group, IIRC. If you do only the > first part then you only get wxcore, which isn't so useful. > > -- > brandon s. allbery [linux,solaris,freebsd,perl] allbery(a)kf8nh.com > system administrator [openafs,heimdal,too many hats] allbery(a)ece.cmu.edu > electrical and computer engineering, carnegie mellon university KF8NH > > > >

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no end to the build errors! (wxhaskell, afrp)
by Yang 07 Jan '07

07 Jan '07

argh, still more build errors on various fronts. i'm using ghc-6.6 on fedora core 5 unless otherwise noted. thanks in advance for help on any of these. a lot of this is part of my attempt to learn more about and play with a high-level functional gui library (and, of course, for getting a better grasp on what frp and arrows are all about) after realizing that i would never ever be able to get fruit working. i have so far found wxfruit (built on wxhaskell) and FG (built on gtk). i am interested in implementing a similarly 'highly-declarative' ui library built on hscurses.widgets. == wxhaskell-0.9.4 == $ make ... wx/src/Graphics/UI/WX/Types.hs:94:0: Bad interface file: out/wx/imports/Graphics/UI/WXCore/Types.hi Something is amiss; requested module wx:Graphics.UI.WXCore.Types differs from name found in the interface file wxcore:Graphics.UI.WXCore.Types make: *** [out/wx/imports/Graphics/UI/WX/Types.o] Error 1 == afrp-0.4 == after removing all references to packages 'lang' and 'concurrent' and changing all "import IORef" to "import Data.IORef as IORef": ghc -c -fglasgow-exts -O -o AFRPUtilities.o AFRPUtilities.hs AFRPUtilities.hs:169:46: Ambiguous occurrence `>>^' It could refer to either `>>^', defined at AFRPUtilities.hs:106:2 or `>>^', imported from AFRP at AFRPUtilities.hs:90:0-10 AFRPUtilities.hs:178:27: Ambiguous occurrence `>>^' It could refer to either `>>^', defined at AFRPUtilities.hs:106:2 or `>>^', imported from AFRP at AFRPUtilities.hs:90:0-10 AFRPUtilities.hs:184:46: Ambiguous occurrence `>>^' It could refer to either `>>^', defined at AFRPUtilities.hs:106:2 or `>>^', imported from AFRP at AFRPUtilities.hs:90:0-10 AFRPUtilities.hs:246:32: Ambiguous occurrence `^>>' It could refer to either `^>>', defined at AFRPUtilities.hs:103:2 or `^>>', imported from AFRP at AFRPUtilities.hs:90:0-10 AFRPUtilities.hs:247:33: Ambiguous occurrence `^>>' It could refer to either `^>>', defined at AFRPUtilities.hs:103:2 or `^>>', imported from AFRP at AFRPUtilities.hs:90:0-10 AFRPUtilities.hs:304:62: Ambiguous occurrence `>>^' It could refer to either `>>^', defined at AFRPUtilities.hs:106:2 or `>>^', imported from AFRP at AFRPUtilities.hs:90:0-10 == FG == $ ghc --make FG.hs [1 of 1] Compiling FG ( FG.hs, FG.o ) FG.hs:115:31: Module `Graphics.UI.Gtk' does not export `button' FG.hs:115:39: Module `Graphics.UI.Gtk' does not export `visible' when removing those two `hiding` params: [1 of 1] Compiling FG ( FG.hs, FG.o ) FG.hs:562:69: Couldn't match expected type `w' (a rigid variable) against inferred type `Bool' `w' is bound by the polymorphic type `forall w. (ToggleButtonClass w) => w -> IO ()' at FG.hs:562:54-92 Expected type: w -> IO () Inferred type: Bool -> IO () In the first argument of `ToggleButtonP', namely `(toggleButtonSetActive p)' In the expression: ToggleButtonP (toggleButtonSetActive p) FG.hs:587:67: Couldn't match expected type `w' (a rigid variable) against inferred type `Bool' `w' is bound by the polymorphic type `forall w. (CheckButtonClass w) => w -> IO ()' at FG.hs:587:53-90 Expected type: w -> IO () Inferred type: Bool -> IO () In the first argument of `CheckButtonP', namely `(toggleButtonSetActive p)' In the expression: CheckButtonP (toggleButtonSetActive p)

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ANN: Yampa + GADT for ghc 6.6
by Joel Reymont 07 Jan '07

07 Jan '07

Folks, This is a raw version of cabalized Yampa + GADT for ghc 6.6. darcs get http://wagerlabs.com/yampa I would like to change the layout of the directory tree and I think there should be a single Cabal file that builds the source, tests and examples. I'm not sure if this is possible, though, as examples and tests depend on the library itself. Regardless, please send your comments and patches and in the meantime just follow the regular Cabal procedure in src, tests and examples. Thanks, Joel -- http://wagerlabs.com/

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Literate Haskell source files. How do I turn them into something I can read?
by Michael T. Richter 07 Jan '07

07 Jan '07

I'm trying to wrap my mind around the darcs source code as a preliminary to looking into GHC's guts. All of darcs is written as .lhs files which have bizarre mark-up in them which distracts me from the actual Haskell source I'm trying to figure out and get used to. Apparently the GHC compiler can take .lhs files, strip them with "unlit" (a utility which I finally found buried deep in the GHC installation -- off-path) and then compile them normally. The problem I have is that unlit leaves behind instead these huge gaping (and highly distracting) stretches of whitespace while it takes out the markup. Are there any tools which I can use to render .lhs files readable? I'm fine with having them converted into documented source (i.e. source code embedded in documentation) or as pure Haskell source (but without the huge whitespace gaps) -- but I can't figure out how to get either. -- Michael T. Richter Email: ttmrichter(a)gmail.com, mtr1966(a)hotpop.com MSN: ttmrichter(a)hotmail.com, mtr1966(a)hotmail.com; YIM: michael_richter_1966; AIM: YanJiahua1966; ICQ: 241960658; Jabber: mtr1966(a)jabber.cn "I think it is very beautiful for the poor to accept their lot [...]. I think the world is being much helped by the suffering of the poor people." --Mother Theresa

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