August 2008 - Haskell-Cafe

Re: Is www.haskell.org down?
by Don Stewart 15 Aug '08

15 Aug '08

By the way, for those wondering why Jon Harrop would say such an unusual thing on the Haskell list, have a look at his contributions over on the OCaml list, http://article.gmane.org/gmane.comp.lang.caml.general/43430 Some choice quotes: "almost all of the examples of Haskell's use in industry are fakes" "nobody has ever done anything significant using Haskell" Jon's the primary source of FUD against Haskell and its community, as he goes around promoting his site in other functional programming communities. This kind of behaviour's been going on for a few years now, sadly. It's all rather disappointing. -- Don

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searchmonkey for haskell apis
by brad clawsie 15 Aug '08

15 Aug '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 i've been looking into the possibility of creating some xslt to expose haskell apis to yahoo search via searchmonkey. if you see the java api search plugin, you can see some possibilities. i was wondering if anyone maintaining any the official api docs had considered looking at searchmonkey. from a site owner's perspective, some rdf metadata can be inlined with the api docs which yahoo will automatically crawl to build up a search corpus, which could then be rendered into a display using the searchmonkey tools. this approach would be superior to the xslt approach i suggest above, since it exposes industry standard metadata that any search engine can use. the xslt approach is an option yahoo offers to let third-parties "scrape" sites they want put in ysearch. since two parties approaches might conflict, i thought i would send out a note. thanks. brad -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkigzvsACgkQxRg3RkRK91MwiACeJ66+jYgPfKvoYCDNYsUulnTo 308An3NrwfkGAgfWJud4MaggHf0Zh9vw =n/9o -----END PGP SIGNATURE-----

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Is www.haskell.org down?
by Sean Leather 15 Aug '08

15 Aug '08

I can't reach www.haskell.org , and I'm having withdrawal issues. Sean

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haskell.org is down
by Benjamin L.Russell 15 Aug '08

15 Aug '08

I tried posting a message to the haskell-beginners mailing list about a half-hour ago, but it seems that all of haskell.org has been down for at least the past half-hour. If anybody on this mailing list responsible for server maintenance receives this message, could you please check into this matter? I would like to be able to post messages on the haskell-related mailing lists, but I can't even get the list of mailing lists to come up, much less post. -- Benjamin L. Russell

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Re: [Haskell-cafe] Bug with QuickCheck 1.1 and GHC 6.8.2
by Patrick Perry 15 Aug '08

15 Aug '08

The bug is in the "variant" function in QuickCheck. I replaced variant :: Int -> Gen a -> Gen a variant v (Gen m) = Gen (\n r -> m n (rands r !! (v+1)) where rands r0 = r1 : rands r2 where (r1, r2) = split r0 with variant :: Int -> Gen a -> Gen a variant v (Gen m) = Gen (\n r -> m n (rands r !! v')) where v' = abs (v+1) `mod` 10000 rands r0 = r1 : rands r2 where (r1, r2) = split r0 and now everything works fine. "10000" seems like a reasonable value here, but one could hard-code a lower or higher value as well. Can someone make sure this gets fixed in the next version of QuickCheck? I'm not sure who the maintainer is. Patrick

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Fwd: ANN: Initial release of Language.C
by Benedikt Huber 15 Aug '08

15 Aug '08

Hello, I'm forwarding this to cafe, in case some of you are interested in this as well but not subscribed to libraries. Again, feedback is most welcome. I've almost finished integrating Language.C with c2hs too (fixing a few bugs along the way), so there will be a quite complex example available soon. Thanks for your interest. Begin forwarded message to libraries(a)haskell.org: > From: Benedikt Huber <benjovi(a)gmx.net> > Date: 13. August 2008 15:45:50 GMT+02:00 I'm pleased to announce the first release of Language.C, a library for analysing and generating C code. This release features * A reasonably well tested parser handling and recording all of C99 and most GNU extensions, most notably gcc's attribute syntax. * A pretty printer generating source code from the AST, covering the same language subset as the parser. * A preview of the analysis framework, including functionality for dissecting C's cruel type and variable declarations. Places: * The project's homepage is located at http://www.sivity.net/projects/language.c (Getting Started, Bug Tracker) * The package is available via hackage (language-c-0.3) * darcs repo: http://code.haskell.org/language-c * API docs: http://code.haskell.org/~bhuber/docs/language-c-latest/ The library originated from the C-related code in c2hs (http://www.cse.unsw.edu.au/~chak/haskell/c2hs/ ), and is the topic of my SoC project, mentored by Iavor Diatchki. (Iavor, Don Steward and Duncan Coutts provided great support, thank you) Feedback and suggestions in any form are most welcome, especially because there is a large range of features which could be implemented. The current status and a few ideas for the next releases are summarized at http://www.sivity.net/projects/language.c/wiki/ ProjectPlan. best regards, benedikt

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Haskell equivalent toPerl stat function
by A Smith 15 Aug '08

15 Aug '08

Hi I'm new to Haskell, so correct me if this is the wrong list or the wrong question. I'm looking for a function similar to the Perl stat to provide me with the last modify time of a file. I've been poring over source code entries referencing hfileSize but can't find the specific bit which reads the directory entry, so I could copy the code. Any advice would be welcome. -- Andrew in Edinburgh,Scotland

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Bug with QuickCheck 1.1 and GHC 6.8.2
by Patrick Perry 14 Aug '08

14 Aug '08

I'm running into problems with generating an arbitrary function of type Double -> Double. Specifically, the following code: {-# LANGUAGE PatternSignatures #-} import Test.QuickCheck import Text.Show.Functions prop_ok (f :: Double -> Double) = f (-5.5) `seq` True prop_bug (f :: Double -> Double) = f (-5.6) `seq` True main = do putStr "prop_ok:\t" >> quickCheck prop_ok putStr "prop_bug:\t" >> quickCheck prop_bug On an Intel Core 2 Duo running Mac OS 10.5.4 with GHC 6.8.2 the output I get is prop_ok: OK, passed 100 tests. prop_bug: Test: Prelude.(!!): negative index On Intel Xeon running RedHat with GHC 6.8.2 both tests hang. Has anyone seen this before? Is it fixed in QuickCheck2? Thanks, Patrick

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Haskell Weekly News: Issue 81 - August 13, 2008
by Brent Yorgey 14 Aug '08

14 Aug '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20080813 Issue 81 - August 13, 2008 --------------------------------------------------------------------------- Welcome to issue 81 of HWN, a newsletter covering developments in the [1]Haskell community. This week saw some interesting talks at [2]AngloHaskell, and some cool new packages to hit Hackage, like [3]Language.C, [4]AERN-Real, [5]FTGL, and [6]Hoogle. What are you waiting for? Get out there and build something! Announcements Initial release of Language.C (language-c-0.3). Benedikt Huber [7]announced the [8]first release of [9]Language.C, a library for analysing and generating C code. This release features a reasonably well tested parser, a pretty printer, and a preview of the analysis framework. darcs roadmap. Jason Dagit [10]wrote to the list to thank everyone for their support for darcs, and to announce a webpage with a [11]roadmap for future darcs features. Darcs is alive and well! Anglo Haskell 2008 -- slides and audio. Matthew Sackman [12]announced that [13]slides and audio from Anglo Haskell 2008 are now available. BLAS bindings for haskell, version 0.5. Patrick Perry [14]announced a new release of the Haskell BLAS bindings, including a number of new features and improvements. Tutorial on information visualization and visual analytics in Haskell. Jefferson Heard [15]announced the [16]tutorial he will be presenting at DEFUN 2008, to give everyone a sneak peek at the long version of the tutorial before he's done with it. Comments and questions are welcome and encouraged. interval and polynomial enclosure arithmetics. Michal Konecny [17]announced the release of the [18]AERN-Real and [19]AERN-RnToRm packages, which model and reasonably efficiently implement exact real arithmetic. FTGL 1.0. Portable truetype font rendering in OpenGL. Jefferson Heard [20]announced the release of [21]Haskell bindings to FTGL, an easy to use library for portable rendering of TrueType fonts in OpenGL. Google Summer of Code Progress updates from participants in the 2008 [22]Google Summer of Code. GHC plugins. Max Bolingbroke is working on dynamically loaded plugins for GHC. [23]This week, he gave [24]a talk at AngloHaskell. Language.C. Benedikt Huber (visq) is [25]working on Language.C, a standalone parser/pretty printer library for C99. This week, he [26]announced the [27]first release of the [28]Language.C package. Hoogle 4. Neil Mitchell (ndm) is working on [29]Hoogle 4. [30]This week, he released several [31]command-line versions and a [32]web version of Hoogle 4, updated the manual, and gave [33]a talk at AngloHaskell. Next week, he plans to work on generating better Hoogle databases, and some bug fixes. DPH physics engine. Roman Cheplyaka (Feuerbach) is working on a [34]physics engine using [35]Data Parallel Haskell. [36]This week, he added complete support for general polyhedra, and fixed some bugs in the collision handler. He also added support for bounding spheres, although the results so far are disappointing, due to delays in the GHC implementation of parallel arrays. Next week, he plans to implement static bodies and BSP trees. Generic tries. Jamie Brandon is working on a library for efficient maps using generalized tries. GHC API. Thomas Schilling (nominolo) is working on [37]improvements to the GHC API. Cabal dependency framework. Andrea Vezzosi (Saizan) is working on a [38]make-like dependency analysis framework for Cabal. Blog noise [39]Haskell news from the [40]blogosphere. * >>> Nicholas Lativy: [41]Haskell in less than five minutes. Nicholas refreshes his memory of Haskell. * Douglas M. Auclair (geophf): [42]Monoid use. * Roman Cheplyaka: [43]Status report: week 11-12. * Douglas M. Auclair (geophf): [44]Combinatory Birds as Types. * Douglas M. Auclair (geophf): [45]Getting Better, part ][. * Neil Mitchell: [46]GSoC Hoogle: Week 11. * Max Bolingbroke: [47]Compiler Plugins AngloHaskell Talk. * London Haskell Users Group: [48]Video: Paradise, a DSEL for Derivatives Pricing. * Roman Cheplyaka (Feuerbach): [49]Compiling GHC. Roman records his experiences building the latest development version of GHC. * Luke Palmer: [50]Mindfuck: The Reverse State Monad. * Dan Piponi (sigfpe): [51]Untangling with Continued Fractions: Part 0. * Joachim Breitner: [52]Xmonad on my mobile phone. * Luke Palmer: [53]Composable Input for Fruit. * >>> Louis: [54]A Gentle Introduction to Haskell. Louis is learning Haskell by working through the Gentle Introduction. * >>> Bryan St. Amour: [55]Some Project Euler. Bryan learns some Haskell the good old-fashioned way---by solving Project Euler problems. * Magnus Therning: [56]TagSoup, meet Parsec!. Magnus uses Parsec to parse streams of tags. * Thomas M. DuBuisson: [57]hsXenCtrl and pureMD5. * Alpheccar: [58]Haskell, iPhone and Biotech. * >>> codeflow: [59]About AI and neural networks. codeflow implements neural networks in Haskell for some soccer-playing AI software. * >>> Vincent Kriek: [60]And the winner is.... Vincent decides to stick with xmonad. * >>> Matthew Trinneer: [61]A New Paradigm - Haskell and HAppS. Quotes of the Week * Anatoly Yakovenko: theory doesn't scare me. i am using haskell after all, so i am used to reading long winded papers. * bwr: mapM_ putStrLn$reverse[(++)([1..y-30]>>" ")$concat$map([" "," /", " -", " \\"]!!)[(foldr(.)(scanl(+)1)([1..y]>>[scanl(+)0])[2..]!!(2*(1+y)+x) )`mod`4|x<-[-y-2..59-y*2]]|y<-[30..61]] About the Haskell Weekly News New editions are posted to [62]the Haskell mailing list as well as to [63]the Haskell Sequence and [64]Planet Haskell. [65]RSS is also available, and headlines appear on [66]haskell.org. To help create new editions of this newsletter, please see the information on [67]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [68]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://www.wellquite.org/anglohaskell2008/ 3. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/language%2Dc 4. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/AERN-Real 5. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/FTGL 6. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hoogle 7. http://article.gmane.org/gmane.comp.lang.haskell.libraries/9809 8. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/language%2Dc 9. http://www.sivity.net/projects/language.c 10. http://www.haskell.org//pipermail/haskell-cafe/2008-August/045959.html 11. http://wiki.darcs.net/DarcsWiki/Roadmap 12. http://www.haskell.org//pipermail/haskell-cafe/2008-August/045986.html 13. http://www.wellquite.org/anglohaskell2008/ 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/43036 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/42994 16. http://bluheron.europa.renci.org/docs/BeautifulCode.pdf 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16368 18. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/AERN-Real 19. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/AERN-RnToRm 20. http://article.gmane.org/gmane.comp.lang.haskell.cafe/42955 21. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/FTGL 22. http://hackage.haskell.org/trac/summer-of-code/wiki/SoC2008 23. http://blog.omega-prime.co.uk/2008/08/11/compiler-plugins-anglohaskell-talk/ 24. http://www.wellquite.org/anglohaskell2008/ 25. http://www.sivity.net/projects/language.c/wiki/ 26. http://article.gmane.org/gmane.comp.lang.haskell.libraries/9809 27. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/language%2Dc 28. http://www.sivity.net/projects/language.c 29. http://code.haskell.org/hoogle/ 30. http://neilmitchell.blogspot.com/2008/08/gsoc-hoogle-week-11.html 31. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hoogle 32. http://haskell.org/hoogle/beta/ 33. http://www.wellquite.org/anglohaskell2008/ 34. http://haskell.org/haskellwiki/Hpysics 35. http://www.haskell.org/haskellwiki/GHC/Data_Parallel_Haskell 36. http://physics-dph.blogspot.com/2008/08/status-report-week-11-12.html 37. http://hackage.haskell.org/trac/ghc/wiki/GhcApiStatus 38. http://code.haskell.org/~Saizan/cabal 39. http://planet.haskell.org/ 40. http://haskell.org/haskellwiki/Blog_articles 41. http://blog.lativy.org/2008/08/13/haskell-in-less-than-five-minutes/ 42. http://logicaltypes.blogspot.com/2008/05/monoid-use.html 43. http://physics-dph.blogspot.com/2008/08/status-report-week-11-12.html 44. http://logicaltypes.blogspot.com/2008/08/combinatory-birds-as-types.html 45. http://logicaltypes.blogspot.com/2008/08/getting-better-part.html 46. http://neilmitchell.blogspot.com/2008/08/gsoc-hoogle-week-11.html 47. http://blog.omega-prime.co.uk/2008/08/11/compiler-plugins-anglohaskell-talk/ 48. http://www.londonhug.net/2008/08/11/video-paradise-a-dsel-for-derivatives-p… 49. http://ro-che.blogspot.com/2008/08/compiling-ghc.html 50. http://luqui.org/blog/archives/2008/08/10/mindfuck-the-reverse-state-monad/ 51. http://sigfpe.blogspot.com/2008/08/untangling-with-continued-fractions.html 52. https://www.joachim-breitner.de/blog/archives/300-Xmonad-on-my-mobile-phone… 53. http://luqui.org/blog/archives/2008/08/09/composable-input-for-fruit/ 54. http://lbks23.wordpress.com/2008/08/09/a-gentle-introduction-to-haskell/ 55. http://bryanstamour.com/?p=46 56. http://therning.org/magnus/archives/367 57. http://tommd.wordpress.com/2008/08/07/hsxenctrl-and-puremd5/ 58. http://www.alpheccar.org/en/posts/show/92 59. http://codeflow.wordpress.com/2008/08/03/about-ai-and-neural-networks/ 60. http://www.vincentkriek.nl/post/and-the-winner-is/ 61. http://thespohtexperiment.blogspot.com/2008/08/new-paradigm.html 62. http://www.haskell.org/mailman/listinfo/haskell 63. http://sequence.complete.org/ 64. http://planet.haskell.org/ 65. http://sequence.complete.org/node/feed 66. http://haskell.org/ 67. http://haskell.org/haskellwiki/HWN 68. http://code.haskell.org/~byorgey/code/hwn/

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Re: ``Orphan instances'' should be avoided anyway.
by Yitzchak Gale 13 Aug '08

13 Aug '08

<Moving from libraries to haskell-cafe...> I wrote: >> ...there must be some >> way to control the import and export of instances, just as we can >> now control the import and export of every other kind of symbol >> binding. Henning Thielemann wrote: > For me it's most often the case that an instance is missing. > If there is no way to change existing instance definitions, > then you must use 'newtype'. Yes, in that case newtype is a work-around, often messy. > Generalized newtype deriving simplifies to adapt the instances you want. That's only one part of it. Using a newtype can sometimes spew wreckage all over the place. But a more difficult case is when you need to use two libraries that already define conflicting instances. That requires a newtype plus however many adaptor functions you need, all inside a wrapper module. What a mess. These cases are likely to arise most often in large software projects. So there hasn't been a big enough demand yet for this feature to be implemented in any compiler, resulting in it being rejected from Haskell', unfortunately. But for large projects it has to work the other way around - the language features need to be there already for the language to be adopted for the project. Or to keep project managers from cursing themselves later on if they do choose Haskell. Anyway, I find the current behavior to be ugly and unintuitive. Why is it that when I say import Control.Monad.Error (throwError, runErrorT) there is no way to prevent also getting a surprising Monad Either instance? Never mind how things should have been named in Control.Monad.Error - that's the way it is right now. I need to be able to import the module without getting the instance. Regards, Yitz

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