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parsec - source position information
by Ozgur Akgun 07 Apr '11

07 Apr '11

Hi, Is there a way to get source position[1] information from parsec while defining a parser? It surely knows about source positions, as they are used while reporting a parsing error. data Identifier = Identifier String SourcePos pIdentifier :: Parser Identifier pIdentifier = do pos <- ?? s <- pString return (Identifier s pos) [1] http://hackage.haskell.org/packages/archive/parsec/3.0.0/doc/html/Text-Pars… Thanks in advance, Ozgur

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Local copy of hackageDB
by José Pedro Magalhães 07 Apr '11

07 Apr '11

Hi all, I want to use cabal-install on a machine without internet access. I tried downloading http://hackage.haskell.org/cgi-bin/hackage-scripts/archive.tar, unpacking it and setting the local-repo field in the config file to this location but that doesn't work, as cabal-install says that it is missing the package list for the local repo. What should I do? Thanks, Pedro

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ANNOUNCE: swish 0.3.0.0
by Doug Burke 07 Apr '11

07 Apr '11

I am pleased to announce an update of the swish package to version 0.3.0.0 [1]. It is mainly meant to be a maintenance upgrade over the existing version on Hackage [2] by Vasili I. Galchin, but does add additional functionality in that it now supports the NTriples format and the N3 parser and formatter has been updated to better match the current specification. For those not aware of what Swish actually is, it is an experiment by Graham Klyne in writing a "Semantic Web" framework in Haskell [3]. I note that the wonderful machinery behind Hackage has already processed the documentation so you can read more about it at [1] as well as the very-sparsely-documented Wiki at [4]. [1] http://hackage.haskell.org/package/swish-0.3.0.0 [2] http://hackage.haskell.org/package/swish-0.2.1 [3] http://www.ninebynine.org/Software/swish-0.2.1.html [4] https://bitbucket.org/doug_burke/swish/wiki/Home Thanks for reading this far, Doug

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ANNOUNCE: DocTest-0.2.0
by Simon Hengel 07 Apr '11

07 Apr '11

I just uploaded a new version of DocTest[1] to Hackage. WHAT IS DocTest? ================ DocTest is a port of Python's doctest[2] to Haskell. It can be used to verify, that examples in Haddock comments[3] do still work. This also provides you with a simple mechanism to write unit test, without the burden of maintaining a dedicated test suite. A basic example of usage is at [4]. WHAT'S NEW IN THIS VERSION? =========================== Support for blank lines in the result of an expression (analogous to the <BLANKLINE>-feature of Python's doctest). Here is an example of usage: -- | -- Some example: -- -- >>> putStrLn "foo\n\nbar" -- foo -- <BLANKLINE> -- bar Currently this is implemented in DocTest, but we will move it to Haddock with the next release. Cheers, Simon [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/DocTest [2] http://docs.python.org/library/doctest.html [3] http://www.haskell.org/haddock/doc/html/ch03s08.html#id566093 [4] http://haskell.org/haskellwiki/DocTest _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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mtlx has a nice design but is slow
by Sean Leather 07 Apr '11

07 Apr '11

I just refactored my type and transform system prototype (introduced in [1] but changed since then) from using mtlx [2] (type-indexed monad transformers described in [3]) to mtl using RWST. mtlx allowed me to cleanly separate the various monadic components in a convenient way. Unfortunately, I found it to be too slow. The refactoring was an experiment to see how slow. I was rather surprised: Running time of a compiled main with a list of tests: mtlx (7 transformers): 2 min 52 sec mtl (RWST): 0 min 13 sec It's frustrating to see such a huge performance gap for a better design. Regards, Sean [1] http://splonderzoek.blogspot.com/2011/03/draft-type-changing-program-improv… [2] http://hackage.haskell.org/package/mtlx [3] http://www.ittc.ku.edu/~marks/cgi-bin/pubs/monadfactory.pdf

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Haskell Weekly News: Issue 176
by Daniel Santa Cruz 07 Apr '11

07 Apr '11

Welcome to issue 176 of the HWN, a newsletter covering developments in the [1]Haskell community. This release covers the week of March 27 to April 02, 2011. You can find the HTML version at: http://bit.ly/fEdQka Announcements Wren Ng Thornton [2]announced the release of version 0.3.4 of unix-bytestring. Ian Lynagh and the GHC team [3]announced version 7.0.3 of GHC, containing a handful of bugfixes. Jose A. Ortega Ruiz [4]annouced the release of version 0.13 of xmobar. Might want to check it out specially if you are using xmonad! Jason Dagit [5]annouced release 0.2.0 of the nehe-tuts package, tutorials for using OpenGL. David Sorokin [6]annouced the release of his new library aivika: a multi-paradigm simulation library. Tom Hawkins [7]annouced version 0.3.1 of ImProve: an imperative DSL for hard realtime embedded applications. Eric Y. Kow [8]introduced the first issue of Parallel Haskell Digest, "a newsletter aiming to show off all the work that's going on using parallelism and concurrency in the Haskell community." Here is to hoping we get more of these! George Giorgidze [9]announced version 0.5.5 of DSH (Database Supported Haskell). Jasper Van der Jeugt [10]annouced the 7th Ghent Functional Programming Group meeting on Tuesday, April 26, in celebration of the group's first year of existance. The meetup will be at the Technicum building of Ghent University at 19:30. Quotes of the Week * lispy: [in response to "C++ is a huge language, the type system is complex"] real and imaginary components :) the imaginary bits are the type safety * gwern: amazing `catch` (how sweet the type), that saved an exception like me! I once was thrown, but now am caught; was impure, but now pure be * hpc: appEndo sounds like a harry potter spell * monochrom: yeah, get out of Turing tarpit, provable termination, only to get into Godel tarpit * xplat: to me, the great thing about pointfree programming is you don't have to let variable names get in the way of your logic. and the great thing about pointful programming is you don't have to let '(flip .) . (.) . (flip flip . join)' get in the way of your logic. it's nice to have multiple tools in your toolbox * lispy: I've never looked at the gtk2hs source. I'm not sure I can muster the intestinal fortitude * kmc: time to play "transfinite ordinal or asian emoticon" * killing-joke: rip oop. "Object-oriented programming is eliminated entirely from the introductory curriculum, because it is both anti-modular and anti-parallel by its very nature, and hence unsuitable for a modern CS curriculum." Top Reddit Stories * Promo code to get Learn You a Haskell 40% off + e- book for free + swag From (learnyouahaskell.com) scored 68 with 25 comments. Read on [11]reddit. Read the [12]original post. * Real Time Edge Detection in Parallel Haskell From (disciple-devel.blogspot.com) scored 39 with 9 comments. Read on [13]reddit. Read the [14]original post. * Modern OpenGL with Haskell From (arcadianvisions.com) scored 39 with 10 comments. Read on [15]reddit. Read the [16]original post. * GHC migration to Git complete From (haskell.org) scored 37 with 15 comments. Read on [17]reddit. Read the [18]original post. * Haskell is 21 years old today! From (twitter.com) scored 37 with 8 comments. Read on [19]reddit. Read the [20]original post. * Re-implementing XMonad's core in Coq : Wouter Swiestra :: PDF From (cs.ru.nl), scored 34 with 13 comments. Read on [21]reddit. Read the [22]original post. * GHC 7.0.3 released From (haskell.org) scored 33 with 9 comments. Read on [23]reddit. Read the [24]original post. * "Reactive-banana and the essence of FRP". I implemented a small FRP library that can be mixed freely with imperative code. From (apfelmus.nfshost.com) scored 30 with 7 comments. Read on [25]reddit. Read the [26]original post. * New release of OpenGL NeHe tutorials in Haskell From (self.haskell), scored 27 with 22 comments. Read on [27]reddit. * Do you read academic papers on a Kindle? From (dmwit.com) scored 26 with 27 comments. Read on [28]reddit. Read the [29]original post. Top StackOverflow Questions * [30]Implementing lazy functional languages votes: 19, answers: 3 * [31]Is it possible to roll your own syntax sugar (like do-notation, or arrow-notation) in Haskell? votes: 12, answers: 2 * [32]Are there any LL Parser Generators for Functional Languages such as Haskell or Scala? votes: 11, answers: 4 * [33]Programming language for functional parallelism: F# vs Haskell votes: 10, answers: 6 * [34]easy "undo" in functional data structures votes: 8, answers: 2 About the Haskell Weekly News If you have any comments/thoughts on the newsletter, don't hesitate to contact me at dstcruz(a)gmail.com. Happy coding! Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.libraries/15521 3. http://article.gmane.org/gmane.comp.lang.haskell.general/18607 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87583 5. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87584 6. http://article.gmane.org/gmane.comp.lang.haskell.general/18612 7. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87628 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87709 9. http://article.gmane.org/gmane.comp.lang.haskell.general/18635 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87752 11. http://www.reddit.com/r/haskell/comments/ge10y/promo_code_to_get_learn_you_… 12. http://learnyouahaskell.com/ 13. http://www.reddit.com/r/haskell/comments/gdudz/real_time_edge_detection_in_… 14. http://disciple-devel.blogspot.com/2011/03/real-time-edge-detection-in-hask… 15. http://www.reddit.com/r/haskell/comments/gepfm/modern_opengl_with_haskell/ 16. http://www.arcadianvisions.com/blog/?p=224 17. http://www.reddit.com/r/haskell/comments/ggu2r/ghc_migrati%C3%B6n_t%C3%B6_g… 18. http://www.haskell.org/pipermail/cvs-ghc/2011-April/060798.html 19. http://www.reddit.com/r/haskell/comments/ggwv3/haskell_is_21_years_old_toda… 20. http://twitter.com/donsbot/status/54026417721188352 21. http://www.reddit.com/r/haskell/comments/gf3sb/reimplementing_xmonads_core_… 22. http://www.cs.ru.nl/~wouters/Talks/BrouwerExtraction.pdf 23. http://www.reddit.com/r/haskell/comments/gcmsz/ghc_703_released/ 24. http://www.haskell.org/pipermail/haskell/2011-March/022673.html 25. http://www.reddit.com/r/haskell/comments/gd46d/reactivebanana_and_the_essen… 26. http://apfelmus.nfshost.com/blog/2011/03/28-essence-frp.html 27. http://www.reddit.com/r/haskell/comments/gcsi1/new_release_of_opengl_nehe_t… 28. http://www.reddit.com/r/haskell/comments/gfz5k/do_you_read_academic_papers_… 29. http://dmwit.com/pdfsplit 30. http://stackoverflow.com/questions/5451645/implementing-lazy-functional-lan… 31. http://stackoverflow.com/questions/5450003/is-it-possible-to-roll-your-own-… 32. http://stackoverflow.com/questions/5507665/are-there-any-ll-parser-generato… 33. http://stackoverflow.com/questions/5492930/programming-language-for-functio… 34. http://stackoverflow.com/questions/5447054/easy-undo-in-functional-data-str…

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Re: [Haskell-cafe] mtlx has a nice design but is slow
by Mark Snyder 06 Apr '11

06 Apr '11

I'm the author for mtlx, and admittedly I didn't do anything about efficiency when I implemented it. Is there any initial place I ought to look for tips on inlining? I'll start with the pragmas page (http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/pragmas.html) I suppose. I'm happy for any suggestions--optimizing hasn't been one of my focuses, so it's time for me to learn I suppose! I did switch to newtype definitions in the most recent version (0.1.5), which probably helped a lot compared to data definitions, but there are no inline pragmas in use, so perhaps there are some good opportunities for optimization. ~Mark Snyder > >Is the package missing some obvious inlining in the instances? > >> I just refactored my type and transform system prototype (introduced in [1] >> but changed since then) from using mtlx [2] (type-indexed monad transformers >> described in [3]) to mtl using RWST. mtlx allowed me to cleanly separate the >> various monadic components in a convenient way. Unfortunately, I found it to >> be too slow. The refactoring was an experiment to see how slow. I was rather >> surprised: >> >> Running time of a compiled main with a list of tests: >> ? mtlx (7 transformers): 2 min 52 sec >> ? mtl (RWST): 0 min 13 sec >> >> It's frustrating to see such a huge performance gap for a better design. >> >> Regards, >> Sean >>

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Re: [Haskell-cafe] How to contact OpenGL package maintainer (where is Sven?)
by Jason Dagit 06 Apr '11

06 Apr '11

No response yet from Sven after about a month and no one seems to have heard from him in over a year. I'm going to take over for now under the assumption that Sven is missing. == My plans for moving forward == * Assemble an opengl taskforce, a few people have already mentioned an interest in being on the team * clean up the current cabal files (I already wrote patches for that) * put the repos on github to make team collaboration easier * add the RULES that Andy Gill suggested for realToFrac * look at adding instances for MArray so that GLfloat et al can be stored in IOUArrays * add support for opengl 4.x * look at adding deprecation pragmas for deprecated opengl calls * new hackage releases * anything else that comes up Thanks, Jason On Sun, Mar 27, 2011 at 2:11 PM, Jason Dagit <dagitj(a)gmail.com> wrote: > I sent the message below to Haskell-Cafe about a week ago. I got one > response saying that Sven has disappeared in the past but reappeared when > updates were necessary. I still haven't heard from Sven. Now I'm widening > my search. My original email to Sven was on March 11th. > > It looks like the OpenGL packages on hackage[1,2,3,4] have not been > updated in some time. No updates later than Oct 2009. I tried to email > Sven directly using the email address listed on hackage but after over two > weeks I still haven't heard from him. I sent some patches to the opengl list > about a week ago but I noticed that Sven hasn't posted on that list since > Oct 2009 when he released the current version of OpenGLRaw. None of the > public darcs repos have patches newer than Oct 2009. Also, the homepage url > listed in the packages is a 404: > http://www.haskell.org/HOpenGL/ > > My concern is that Sven has disappeared for some reason. I hope he's well. > He has always done top notch work in the past maintaining these libraries. > Perhaps he's simply busy or lost interest? > > Does anyone know if he was looking for a new maintainer? Perhaps you've > heard from him more recently than Oct 2009? > > If a new maintainer is needed, I would consider nominating myself :) > > Thanks, > Jason > > [1] http://hackage.haskell.org/package/OpenGLRaw > [2] http://hackage.haskell.org/package/OpenGL > [3] http://hackage.haskell.org/package/GLURaw > [4] http://hackage.haskell.org/package/GLUT >

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ANN: Hakyll 3.1
by Jasper Van der Jeugt 06 Apr '11

06 Apr '11

Hello all, I've just uploaded Hakyll 3.1.0.0 [1] to Hackage. It contains some backwards-incompatible changes (but they are really for the greater good). The most important change is the matching done in the rules DSL. What used to be written as: route "posts/*" someRoute compile "posts/*" someCompiler Is now written as: match "posts/*" $ do route someRoute compile someCompiler This new style is way more expressive, as you can define custom predicates such as: match (predicate (\i -> matches "foo/*" i && not (matches "foo/bar" i))) $ do ... For more information, see the Pattern documentation [2]. Another slight change is that the `Hakyll.Web.Tags` [3] module now uses an association list instead of a `Data.Map` -- in case you want to change the order in which tags are displayed. If you have any questions or trouble migrating, feel free to drop a mail to me or here [4] or visit us in #hakyll on Freenode. [1]: http://hackage.haskell.org/package/hakyll [2]: http://jaspervdj.be/hakyll/reference/Hakyll-Core-Identifier-Pattern.html [3]: http://jaspervdj.be/hakyll/reference/Hakyll-Web-Tags.html [4]: https://groups.google.com/forum/#!forum/hakyll Cheers, Jasper

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ncurses trouble
by Andrew Pennebaker 06 Apr '11

06 Apr '11

I'm having trouble using Haskell and ncurses Mac OS X (10.6.6 to be precise). GHC 6.12.3 gives me a lot of trouble, and GHC 7.0.2 even more. rogue.hs, is a text adventure game in the works. $ cat rogue.hs {-# LANGUAGE OverloadedStrings #-} import Data.Text import UI.NCurses main :: IO () main = runCurses $ do win <- defaultWindow updateWindow win $ do moveCursor 10 10 drawText "Hello world! Hit 'q' to exit" render waitForQ win waitForQ :: Window -> Curses () waitForQ win = do ev <- getEvent win Nothing case ev of Just (EventCharacter 'q') -> return () _ -> waitForQ win $ sudo port install ncurses ncursesw $ cabal install ncurses Resolving dependencies... Configuring ncurses-0.2... cabal: c2hs version >=0.15 is required but it could not be found. cabal: Error: some packages failed to install: ncurses-0.2 failed during the configure step. The exception was: ExitFailure 1 Hmm. Cabal couldn't find a solution to the c2hs dependency. So I install it manually. $ cabal install c2hs $ cabal install ncurses Resolving dependencies... Configuring ncurses-0.2... cabal: Missing dependency on a foreign library: * Missing C library: ncursesw This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. cabal: Error: some packages failed to install: ncurses-0.2 failed during the configure step. The exception was: ExitFailure 1 MacPorts' ncurses isn't detected by Haskell, so I use Homebrew's. $ brew install ncursesw $ ghc --make -o rogue rogue.hs [2 of 2] Compiling Main ( rogue.hs, rogue.o ) Linking rogue ... ld: warning: in /usr/local/lib/libncursesw.dylib, file was built for unsupported file format which is not the architecture being linked (i386) It appears that the Homebrew ncurses library is x86, and GHC is x86_64, or vice-versa. $ sudo port install ncurses +universal $ sudo port install ncursesw +universal $ brew install --universal ncursesw These don't visibly improve compilation in any way. I thought updating Haskell would fix the problem. $ wget http://lambda.galois.com/hp-tmp/2011.2.0.0/Haskell%20Platform%202011.2.0.0-… $ sudo installer -pkg "Haskell Platform 2011.2.0.0-i386.pkg" -target / $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library But it only made the problem worse. Now ncurses won't even build. $ cabal install ncurses Resolving dependencies... Configuring ncurses-0.2... Preprocessing library ncurses-0.2... Building ncurses-0.2... [1 of 4] Compiling UI.NCurses.Enums ( dist/build/UI/NCurses/Enums.hs, dist/build/UI/NCurses/Enums.o ) [2 of 4] Compiling UI.NCurses.Types ( UI/NCurses/Types.hs, dist/build/UI/NCurses/Types.o ) [3 of 4] Compiling UI.NCurses ( dist/build/UI/NCurses.hs, dist/build/UI/NCurses.o ) [4 of 4] Compiling UI.NCurses.Panel ( dist/build/UI/NCurses/Panel.hs, dist/build/UI/NCurses/Panel.o ) UI/NCurses/Panel.chs:49:1: Warning: The import of `UI.NCurses' is redundant except perhaps to import instances from `UI.NCurses' To import instances alone, use: import UI.NCurses() hsncurses-shim.c:5:29: error: ncursesw/curses.h: No such file or directory cabal: Error: some packages failed to install: ncurses-0.2 failed during the building phase. The exception was: ExitFailure 1 I'd settle for using hscurses, but it won't compile with GHC 7, and it has its own internal bugs besides. $ cabal install hscurses Resolving dependencies... Configuring hscurses-1.4.0.0... configure: WARNING: unrecognized options: --with-gcc checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking for addnstr in -lcurses... yes checking for addnstr in -lncurses... yes checking for waddnwstr in -lncursesw... yes checking for iconv in -liconv... yes checking for libiconv in -liconv... yes checking for libiconv... yes checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /usr/bin/grep checking for egrep... /usr/bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking iconv.h usability... yes checking iconv.h presence... yes checking for iconv.h... yes checking curses.h usability... yes checking curses.h presence... yes checking for curses.h... yes checking ncurses.h usability... yes checking ncurses.h presence... yes checking for ncurses.h... yes checking ncursesw/ncurses.h usability... no checking ncursesw/ncurses.h presence... yes configure: WARNING: ncursesw/ncurses.h: present but cannot be compiled configure: WARNING: ncursesw/ncurses.h: check for missing prerequisite headers? configure: WARNING: ncursesw/ncurses.h: see the Autoconf documentation configure: WARNING: ncursesw/ncurses.h: section "Present But Cannot Be Compiled" configure: WARNING: ncursesw/ncurses.h: proceeding with the preprocessor's result configure: WARNING: ncursesw/ncurses.h: in the future, the compiler will take precedence checking for ncursesw/ncurses.h... yes checking locale.h usability... yes checking locale.h presence... yes checking for locale.h... yes checking langinfo.h usability... yes checking langinfo.h presence... yes checking for langinfo.h... yes checking wchar.h usability... yes checking wchar.h presence... yes checking for wchar.h... yes checking limits.h usability... yes checking limits.h presence... yes checking for limits.h... yes checking signal.h usability... yes checking signal.h presence... yes checking for signal.h... yes configure: creating ./config.status config.status: creating hscurses.buildinfo config.status: creating cbits/config.h configure: WARNING: unrecognized options: --with-gcc cabal: Missing dependency on a foreign library: * Missing (or bad) header file: HSCurses.h This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. If the header file does exist, it may contain errors that are caught by the C compiler at the preprocessing stage. In this case you can re-run configure with the verbosity flag -v3 to see the error messages. cabal: Error: some packages failed to install: hscurses-1.4.0.0 failed during the configure step. The exception was: ExitFailure 1 Cheers, Andrew Pennebaker www.yellosoft.us

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