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Problems installing documentation and sources using Cabal on Mac OSX
by Colin Adams 01 Sep '09

01 Sep '09

I noticed today on the train (no internet connection!) that the documentation for packages I had installed with cabal was missing, and that there was no source in .cabal/packages for them. Now I'm in the offiice, I tried --reinstall --enable-documentation. There was a warning about haddock and ghc version mismatch (so much for the haskell platform install), so I did a --reinstall of haddock. Now the message I see is: cabal: can't find source for module Paths_happstack_server (happstack_server is the first package I'm trying to reinstall to get docs). So I think the documentation failure is because haddock can't find the source code (nor can I), but I don't know why there is no source installed in .cabal/packages - what should I do to further track this problem down? -- Colin Adams Preston, Lancashire, ENGLAND

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Re: [Haskell-cafe] Takusen - is anyone currently using it on Win32 - ODBC?
by Günther Schmidt 01 Sep '09

01 Sep '09

Hi Anton, well the problem isn't really accessing the data as such, it's quite easy to use HDBC.ODBC for instance to read in the data in a very comfortable way. I was explicitly asking for Takusen because it make certain guarantees regarding resources, memory consumption and such. One of the files for instance has 298 k lines. A glance over sushi revealed that parsec is involved so I can only presume it is read into memory all at once. That would certainly be a problem. Thanks, Günther Am 31.08.2009, 19:47 Uhr, schrieb Anton van Straaten <anton(a)appsolutions.com>: > Günther Schmidt wrote: >> My app then needs to read in dynamic data, a set of 4 CSV files, and I >> had been using Microsofts ODBC driver with HDBC.ODBC and that worked >> too. >> When I try to swap it for Takusen though I get an >> *** Exception: DBError ("HY","C00") 106 "[Microsoft][ODBC Text >> Driver] >> Optional Feature was not implemented >> Which is a bit of a shame, because using the ODBC text driver was much >> simpler than parsing the CSV files. > > A simple but powerful way to access CSV files is via TxtSushi, which > gives SQL access to CSV files, without needing ODBC: > > Home page: http://keithsheppard.name/txt-sushi/ > Hackage: http://hackage.haskell.org/package/txt-sushi > > You'd have to use it directly, since afaik it won't work with Takusen, > although a Takusen back end for it ought to be possible. > > Anton >

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How to fix such a TYPE problem ?
by zaxis 01 Sep '09

01 Sep '09

>let [y,m,d] = map (\x -> read x::Int) $ splitRegex (mkRegex "-") "2009-08-31" >fromGregorian y m d Couldn't match expected type `Integer' against inferred type `Int' In the first argument of `fromGregorian', namely `y' In the expression: fromGregorian y m d In the definition of `it': it = fromGregorian y m d thanks! -- View this message in context: http://www.nabble.com/How-to-fix-such-a-TYPE-problem---tp25233906p25233906.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Dutch HUG: meeting next week (September 11th) in Utrecht
by Tom Lokhorst 31 Aug '09

31 Aug '09

>From lovely Edinburgh, I'd like to invite functional programmers in The Netherlands to the Dutch Haskell User Group [1, 2] meeting next Friday at 19:00. For the first time, we'll have people giving talks! Thomas (noknok) will be talking about his system for doing propositional logic in Haskell. Pedro will give an introductory talk about generic programming, and Sean will talk about xformat, a library for extensible and type-safe formatting with scanf- and printf-like functions. If you're interested in giving a short 5-minute lighting talk about something related to Haskell or functional programming, we'd very much like to hear from you! The meeting will be in the Booth Hall [3] of the Utrecht University Library. There's free car parking [4] at the library, and it's easily accessible by bike and bus [5]. We have a poll [6] that shows all people who plan to attend. See you next Friday! - Tom Lokhorst [1]: http://www.haskell.org/haskellwiki/Dutch_HUG [2]: http://groups.google.com/group/dutch-hug [3]: http://www.uu.nl/EN/library/contact/university_library/zaalverhuur/Pages/de… [4]: http://www.uu.nl/EN/library/contact/university_library/Parkeren/Pages/defau… [5]: http://www.uu.nl/EN/library/contact/university_library/plattegrondenrou/Pag… [6]: http://doodle.com/a7vx3a6imcue4ghr

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Get data from HTML pages
by José Romildo Malaquias 31 Aug '09

31 Aug '09

Hello. I am porting to Haskell a Java application I have written to manage collections of movies. Currently the application has an option to indirectly import movie data from web pages. For that first the user should access the page in a web browser. Then the user should copy the rendered text in the web browser into an import window in my application and click an "import" button. In response the application parses the given text and collects any relevant data it knows about, using regular expressions. For instance, to get the director information from a movie in the AllCenter web site I use the following regular expression: ^Direção:\s+(.+)$ I want to modify this scheme in order to eliminate the need to copy the rendered text from a web browser. Instead my application should download and parse the HTML page directly. Which libraries are available in Haskell that would make it easy to get content information from a HTML document, in the way described above? Regards, Romildo

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Takusen ODBC - MS Access
by Günther Schmidt 31 Aug '09

31 Aug '09

Hi all, recently I had problems getting Takusen ODBC to work with MS-Access on Win32. It seems, that the problems originated from Takusens UTF8 code, the path of the Access Database contains an Umlaut. This even causes problems when one does not specify a connection String but merely a DSN, no further problems occured when I moved the Access file directly to C:\. I also could not get takusen to work with MS Text / CSV ODBC driver, irregardless of Umlauts, the exception was about some optional feature not implemented (on MS's ODBC site). Could anyone suggest a work around? I notice that when you're a haskeller on Win32 *and* German (the Umlauts), things become a bit more difficult than for the English / linux haskellers. Günther

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Takusen - is anyone currently using it on Win32 - ODBC?
by Günther Schmidt 31 Aug '09

31 Aug '09

Hi all, is anyone currently using takusen with odbc on Win32? In particular with MS Access? I'm asking because I noticed that when database libraries are declared to work with ODBC no one seems to mean Win32 ODBC, but rather Unix ODBC. Günther

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Re: How to use dyre relaunch/restore State of Gtk2hs Object?
by Will Donnelly 31 Aug '09

31 Aug '09

Hi Andy, Your program didn't compile as given, so I cut out some of the event handling fanciness you were doing. Also, my modified version restarts whenever the 'r' key is pressed. I figure those changes aren't important to the problem at hand. Anyway, I don't think it's ever going to be possible to define a Binary instance for a TextView, since all of the functions which can yield information about it are impure. I would recommend extracting the relevant data beforehand, and then persisting it in a tuple. You could use some 'marshal<WIDGET>' and 'recreate<WIDGET>' functions if you need to persist many different widget types. Saving just the text can be done as follows: <code> module DyreExample where import Graphics.UI.Gtk hiding (get) import qualified Graphics.UI.Gtk.Gdk.Events as E import qualified Config.Dyre as Dyre import Config.Dyre.Relaunch import System.IO import Data.Binary data Config = Config { message :: String, errorMsg :: Maybe String } defaultConfig :: Config defaultConfig = Config "Dyre Example v0.1" Nothing showError :: Config -> String -> Config showError cfg msg = cfg { errorMsg = Just msg } realMain Config{message = message, errorMsg = errorMsg } = do initGUI textView <- textViewNew textBuffer <- textViewGetBuffer textView text <- restoreBinaryState "" putStrLn $ "Restored state: " ++ text textBufferSetText textBuffer text rootWindow <- windowNew rootWindow `onDestroy` mainQuit windowFullscreen rootWindow rootWindow `containerAdd` textView widgetShowAll rootWindow rootWindow `onKeyPress` (\event -> dyreKeyTest event textView) mainGUI dyreExample = Dyre.wrapMain $ Dyre.defaultParams { Dyre.projectName = "Main" , Dyre.realMain = realMain , Dyre.showError = showError } dyreKeyTest :: E.Event -> TextView -> IO Bool dyreKeyTest ev textView = do case E.eventKeyName ev of "r" -> do textBuffer <- textViewGetBuffer textView sI <- textBufferGetStartIter textBuffer eI <- textBufferGetEndIter textBuffer text <- textBufferGetText textBuffer sI eI True putStrLn $ "Relaunching with state: " ++ text relaunchWithBinaryState text Nothing return True _ -> return False </code> Other comments: 1. It isn't necessary to explicitly tell Dyre to do a custom compile. It will take care of figuring that out once you restart it. 2. Instead of manually setting paths in the code, you can use the '--dyre-debug' command-line flag, which will cause Dyre to look for configurations in the current directory, and store temporary files in a 'cache' subdirectory. 3. Giving a project name of 'Main' causes Dyre to see the file 'Main.hs' as a custom configuration. I'm not sure if that's what you intended, but it will make testing custom configurations harder than it needs to be. 4. Good luck with the rest of your project! - Will Donnelly

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Edinburgh Hackathon round-up
by Dougal Stanton 31 Aug '09

31 Aug '09

Hello Haskellers, On Saturday & Sunday (28th & 29th August) we held a Hackathon in Edinburgh, before the ICFP got fully underway. If you were there, thank you for coming. We'll be writing a summary of what happened soon, and we'd love to hear what you did. If you started a new project or fixed some insidious bug, identified a major bottleneck or just enriched the testing structure around your chosen project, it would be great to know. Just a line or two is all we need! I am hoping that everyone who attended will see this message, as they must have seen Eric's original advertising emails. But please pass this message along if you know there's someone we missed. Cheers, Dougal -- Dougal Stanton dougal(a)dougalstanton.net // http://www.dougalstanton.net

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specialised monad transformers
by Alberto G. Corona 31 Aug '09

31 Aug '09

Hi all I want to define a partial monad transformer i.e not defined for all kinds of data but the ones that have instances of certain classes. That is because in my lift instance code there are some hidden use of these classes. But because in the MonadTrans definition does not refers to the data, no specialised lift seems possible: class MonadTrans t where lift :: Monad m => m a -> t m a Is that true? A possible adition could be to define (note: I did not test it, it is just an idea): class SpecialisedMonadTrans (t m a) where lift :: Monad m => m a -> t m a liftMN :: Monad m => m a -> t a The whole problem has certain relation with effect control. This kind of definition permits a more fine control of effect handling when passing from a monad to other depending on the idiosyncrasy of the monad m and the kind of a.

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