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Composing monads
by Maurício 24 Nov '07

24 Nov '07

Hi, If I have two computations a->IO b and b->IO c, can I join them to get an a->IO c computation? I imagine something like a liftM dot operator. Thanks, Maurício

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Polymorphic dynamic typing
by Paulo Silva 23 Nov '07

23 Nov '07

Hello, Type representations using GADTs are being used to achieve dynamic typing in Haskell. However, representing polymorphic types is problematic. Does anyone know any work about including polymorphism in dynamic typing? Best regards, Paulo

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very elementary "import" problem .. help
by Galchin Vasili 23 Nov '07

23 Nov '07

Hello, import System.Posix --import Network import System.Process --import Directory import STM I am loading the above script in ghci. However, System.Posix, System.Processand STM cannot be found. Network and Directory are found. I assume when ghc is installed on Windows that the Windows registry get populated with paths to GHC 'library" directory paths. Please someone tell me why I am having trouble importing these modules/libraries. Kind regards, vasya

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Interrupting threads and ualarm
by ROBERT DOUGLAS HOELZ 23 Nov '07

23 Nov '07

Hello Haskellers, I have two questions for you: * Is there a Haskell binding to the ualarm() function in unistd.h? I looked in System.Posix.Signals, but there's just a binding for alarm(). * Is there a way to interrupt a blocking operation on another thread? I thought about throwTo, but that seems like overkill. Here's some example code: import Control.Concurrent main :: IO () main = do tid <- myThreadId forkIO $ interruptMain tid getChar interruptMain :: ThreadId -> IO () interruptMain mainThreadId = do threadDelay 5000000 interrupt mainThreadId -- This is probably going to end up being throwTo, isn't it?

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c2hs on Windows?
by Alex Young 23 Nov '07

23 Nov '07

Hi all, Does anyone know if c2hs should be working on Windows? I'm trying to build it under ghc 6.8.0, but this happens: C:\Users\Alex\Documents\Plugins\c2hs\c2hs-0.15.0>runghc Setup.hs configure Configuring c2hs-0.15.0... Setup.hs: Error: Non-empty library, but empty exposed modules list. Cabal may not build this library correctly C:\Users\Alex\Documents\Plugins\c2hs\c2hs-0.15.0>runghc Setup.hs build Setup.hs: error reading dist\setup-config; run "setup configure" command? Apologies if I'm being dense... Thanks, -- Alex

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http/ftp library
by Bulat Ziganshin 23 Nov '07

23 Nov '07

Hello Haskell-Cafe, i write a file-processing utility and want to allow users open URLs like the usual files. for this, i need a library with minimum the following http functionality: getFileSize url readBuf url bufPtr offset size ideally, it should also support ftp and allow to create ftp files: h <- create url writeBuf h bufPtr size close h what libraries can i use? ghc 6.6.1, if it's important -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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ANN: Dimensional 0.7.1 (GHC 6.8.1 compatibility)
by Bjorn Buckwalter 23 Nov '07

23 Nov '07

Dear all, The Dimensional library has been ported to GHC 6.8.1 (it remains backwards-compatible with GHC 6.6.1, and also with Cabal 1.1.6 I believe). The new version number is 0.7.1. Due to a GHC 6.8.1 bug (#1919) the CGS module will not compile and has been disabled. Thanks, Bjorn Buckwalter http://dimensional.googlecode.com http://hackage.haskell.org/cgi-bin/hackage-scripts/package/dimensional http://hackage.haskell.org/trac/ghc/ticket/1919

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Digest size
by Simon Marlow 23 Nov '07

23 Nov '07

[ with mailing list maintainer's hat on ] Someone asked me if they could get fewer digests per day from haskell-cafe. The threshold for sending out a digest is currently 30k, which is probably the default, but seems a bit small to me. Any objections to bumping it, to say 100k? Cheers, Simon

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Source code for Visual Haskell
by Felix Martini 23 Nov '07

23 Nov '07

Hi all, The documentation of Visual Haskell mentions that the source code is available under a BSD license. The code is not available from the download page (http://www.haskell.org/visualhaskell/downloads.html) Does anone know where to get it?

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Tetris
by Andrew Coppin 23 Nov '07

23 Nov '07

If you were going to implement Tetris in Haskell, how would you do it? (For that matter, has anybody already *done* it? It would probably make a nice example program...) I'm particularly interested to know 1. How exactly would you do the graphical components? (Presumably there's some deep trickery with Gtk2hs that can draw free-form stuff like this.) 2. How do you implement a program that is fundamentally about state mutation in a programming language which abhors state mutation?

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