December 2011 - Haskell-Cafe

Where threadSleep is defined?
by dokondr 06 Dec '11

06 Dec '11

Hi, I need to make the current process (executing thread) go to sleep for a given amount of time. Can't find where threadSleep is defined. Thanks!

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List x ByteString x Lazy Bytestring
by John Sneer 06 Dec '11

06 Dec '11

Hello Café, I've used Haskell and GHC to solve particular real life application. 4 tools were developed and their function is almost the same - they modify textual input according to patterns found in the text. Thus, it is something like a compiler, the result is also a text and it is not parsed to tokens as patterns appear on a different level. The tools differ in tasks and number of modifications performed, otherwise, in principal, they are very much similar. I used lists (Prelude, Data.List) to develop the tools. After successfully completing the development, I've started to optimize the code to make the tools faster. After modification of some algorithms (which dropped the processing time notably), I started to change data structures. I swapped lists with lazy bytestrings. Nevertheless, what an unpleasant surprise, the processing speed dropped down, significantly / more then 30% time needed). So my questions follow: - What kind of application is lazy bytestring suitable for? - Would it be worth using strict bytestring even if input files may be large? (They would fit in memory, but may consume whole) - If bytestring is not suitable for text manipulation, is there something faster than lists? - It would be nice to have native sort for lazy bytestring - would it be slower than pack $ Data.List.sort $ unpack ? - If bytestring is suitable for text manipulation could we have some hGetTextualContents which translates Windows EOL (CR+LF) to LF? I'm sorry if the answers are obvious. Could anyone point me to some article/pages I could read about? Thanks and regards, John -- http://www.fastmail.fm - A fast, anti-spam email service.

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Complete package description list
by Shakthi Kannan 06 Dec '11

06 Dec '11

Hi, I would like to know: 1. The correct source to get the complete list of available Haskell package descriptions 2. Any feed or notification mechanism to get newer updates on packages How often does the 00-index.tar.gz file from: http://hackage.haskell.org/packages/archive/00-index.tar.gz get updated? Or if there is a newer version, where is it made available? Given 00-index.tar.gz, and using the following RSS feed: http://hackage.haskell.org/packages/archive/recent.rss give me the complete list of available packages? Appreciate any suggestions in this regard, Thanks! SK -- Shakthi Kannan http://www.shakthimaan.com

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ANNOUNCE: monad-control-0.3
by Bas van Dijk 06 Dec '11

06 Dec '11

Hello, I just released monad-control-0.3. The package for lifting control operations (like catch, bracket, mask, alloca, timeout, forkIO, modifyMVar, etc.) through monad transformers: http://hackage.haskell.org/package/monad-control-0.3 It has a new and improved API which is: * easier to understand by explicitly representing the monadic state using type families. * 60 times faster than the previous release! * more general because control operations can now, not only be lifted from IO, but from any base monad (ST, STM, etc.) I also released a new package: lifted-base: http://hackage.haskell.org/package/lifted-base-0.1 It provides lifted versions of functions from the base library. Currently it exports the following modules: * Control.Exception.Lifted * Control.Concurrent.Lifted * Control.Concurrent.MVar.Lifted * System.Timeout.Lifted These are just modules which people have needed in the past. If you need a lifted version of some function, just ask me to add it or send me a patch. Note that Peter Simons just discovered that these packages don't build with GHC-7.0.4 (https://github.com/basvandijk/monad-control/issues/3) I just committed some fixes which enable them to be build on GHC >= 6.12.3. Hopefully I can release these fixes this weekend. Regards, Bas

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Re: [Haskell-cafe] How to get a file path to the program invoked?
by Greg Weber 06 Dec '11

06 Dec '11

In addition to argv[0] http://hackage.haskell.org/packages/archive/system-argv0/0.1/doc/html/Syste… There is also this package: http://hackage.haskell.org/packages/archive/FindBin/0.0.5/doc/html/System-E… System-Argv0 has special cases for windows- FindBin may not work there.

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GHCi and Cairo on Windows
by smeltzek＠eecs.oregonstate.edu 05 Dec '11

05 Dec '11

In effort to keep my work cross-platform, I am trying to get GHCi and Cairo working together nicely on Windows (as a back-end to Diagrams, if it matters.) When loading the library in GHCi I get the following error: Loading package cairo-0.12.2 ... linking ... ghc: unable to load package `cairo-0.12.2' I am able to build, link, and execute successfully using 'ghc --make' so I know the libraries are installed correctly. I'm using GHC as packaged in the most recent version of the Haskell Platform and the most recent all-in-one Windows bundle of GTK. I've seen quite similar errors reported months ago with no apparent solution. Any help would be appreciated! --Karl

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Re: [Haskell-cafe] Poll: Do you want a mascot? -- please stop this
by Giovanni Tirloni 05 Dec '11

05 Dec '11

On Wed, Nov 23, 2011 at 5:52 PM, heathmatlock <heathmatlock(a)gmail.com>wrote: > On Wed, Nov 23, 2011 at 1:40 PM, Alexander Bernauer < > alex-haskell(a)copton.net> wrote: > >> Yes >> >> PS: Why not using Doodle for the poll? >> > > Email is an easy way to make sure nobody votes twice. > 1. It's unlikely to get feedback from the larger Haskell community 2. It floods people with email they don't care (unless they care to keep track of the results) 3. One can just as easily create throw-away emails, subscribe to the list and answer the poll 4. etc... My suggestion is to create a poll somewhere else and let it run for at least a month. Or a more elaborated survey with additional questions trying to capture the community's feeling toward a masket and what kind. I don't think we are in a hurry to get a mascot here so let's take the time and do it properly. -- Giovanni

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Re: [Haskell-cafe] "could not create compact unwind"
by Mark Lentczner 05 Dec '11

05 Dec '11

The ld warning is benign. You can safely ignore it. It is a known issue with GHC and the latest Mac OS X tool chain, and we are stuck with it for awhile: http://hackage.haskell.org/trac/ghc/ticket/5019 The best way to remove versions of Haskell on a Mac is now my shiny new Mac uninstaller! I just put out a "release candidate" yesterday. You can find it here: Source: UninstallHS.hs (just runhaskell this)Executable: uninstall-hs.tgz (unpack and run if your ghc is broken) Running without will just list what's there and suggest what to do next. It is "dry-run" by default. - Mark PS.: "rm -rf ~/.ghc" only removes the package databases, not the packages themselves. It also removes your ghci configuration, so I don't recommend it.

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Re: [Haskell-cafe] How to get a file path to the program invoked?
by dokondr 05 Dec '11

05 Dec '11

Balazs, thanks for your comments! The first comment works just fine. With </> operator I get this: Main System.Environment.Executable System.FilePath> "/abc" </> "/" "/" Instead of getting "/abc/" I get "/". What am I doing wrong? On Mon, Dec 5, 2011 at 6:03 PM, Balazs Komuves <bkomuves(a)gmail.com> wrote: > > Two small comments: > > 1) This should work on Windows too, if you just leave out the word "Posix" > from the source: > import System.FilePath (splitFileName) > > 2) In general when dealing with paths, use the </> operator (from > System.FilePath) > instead of ++ "/" ++ > > Balazs > > > On Mon, Dec 5, 2011 at 1:44 PM, dokondr <dokondr(a)gmail.com> wrote: > >> This is how I finally solved this problem for POSIX complaint system: >> >> -- >> -- TestRun >> -- >> module Main where >> import System.Cmd (rawSystem) >> import System.Directory (getCurrentDirectory) >> import System.Environment.Executable (ScriptPath(..), getScriptPath) >> import System.FilePath.Posix (splitFileName) >> >> main = do >> >> path <- getMyPath >> putStrLn $ "myPath = " ++ path >> let cmdLine = path ++ "args.sh" >> rawSystem cmdLine ["iphone", "test-twitts.txt"] >> >> {-- >> data ScriptPath Source >> >> Constructors: >> Executable FilePath it was (probably) a proper compiled executable >> RunGHC FilePath it was a script run by runghc/runhaskell >> Interactive we are in GHCi >> --} >> >> getMyPath = do >> curDir <- getCurrentDirectory -- from System.Directory >> scriptPath <- getScriptPath -- from System.Environment.Executable >> let path = getMyPath' scriptPath curDir >> return path >> >> getMyPath' (Executable path) _ = fst (splitFileName path) >> getMyPath' (RunGHC path) _ = fst (splitFileName path) >> getMyPath' Interactive curDir = curDir++"/" >> >> >>

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writeFile: commitBuffer: invalid argument (Illegal byte sequence)
by dokondr 05 Dec '11

05 Dec '11

Hi, In GHC 7.0.3 / Mac OS X when trying to: writeFile "someFile" "(Hoping You Have A iPhone When I Do This) Lol Sleep Is When You Close These ---> \55357\56384" I get: commitBuffer: invalid argument (Illegal byte sequence) The string I am trying to write can also be seen here: http://twitter.com/#!/search/Hoping%20You%20Have%20A%20iPhone%20When%20I%20…<http://twitter.com/#%21/search/Hoping%20You%20Have%20A%20iPhone%20When%20I%…> It looks like 'writeFile' can not write unicode characters. Any workarounds? Thanks! Dmitri

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