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Re: Exception handling in numeric computations
by John Lato 26 Mar '09

26 Mar '09

> Message: 15 > From: Xiao-Yong Jin <xj2106(a)columbia.edu> > John Lato <jwlato(a)gmail.com> writes: > > So I have another question. Is the following function safe > and legitimate? > >> safeDiv :: (Exception e, Integral a) => >> a -> a -> Either e a >> safeDiv x y = unsafePerformIO . try . evaluate $ div x y > > I believe it should be okay to use this 'safeDiv'. What do > you think? Your question is unclear. Are you asking if this function can be safely used with current Haskell standards and implementations or are you asking should the Haskell specification make a guarantee that this function will do what you want? I would answer "no" either way, but for different reasons. Common to both is: Don't use unsafe* functions unless you can prove that your usage is safe. That is proof as in mathematical usage; it must be rigorous and complete. John Lato

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Copying data files when installing, using Cabal
by Henk-Jan van Tuyl 26 Mar '09

26 Mar '09

L.S., I am trying to install an application with data files (I am developing that application). These data files are mentioned in the .cabal file, after the "Data-files:" keyword. When I give command "runhaskell setup install", the data files are not copied; how can I correct this? -- Regards, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ --

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[ANN] I/O library for Windows
by Felix Martini 26 Mar '09

26 Mar '09

Hi all, winio is an I/O library for Windows using Windows API functions and has I/O completion port support. The main goal of this library is to support Simon Marlow's new Handle API once he has added that to GHC. The library also has a compatibility module for socket functions from the network-bytestring package. Because the library uses IOCP instead of select it is not limited to 1024 open sockets. Try for example the thread-ring program where each Haskell thread passes a UDP message around (Change the MaxUserPort field in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters to 65534 to enable all ports). The winio package is available on Hackage. Notice that it uses a development version of the network package which is available at http://darcs.haskell.org/packages/network/. The library has not been tested much and should be considered experimental so please try it if you use Windows and notify me of any issue or corner case. Kind Regards, Felix

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Fwd: [Haskell-cafe] Re: ANNOUNCE: WinGhci, a GUI for GHCI on Windows
by Pepe Gallardo 26 Mar '09

26 Mar '09

2009/3/23 Andrew Butterfield <Andrew.Butterfield(a)cs.tcd.ie> > Benjamin L.Russell wrote: > >> This is wonderful--just what I was waiting for! The application looks >> beautiful, and I'm very happy that GHCi now has a matching GUI >> application along the lines of WinHugs. >> >> > Indeed - me too ! > >> It would be even better if you could provide some >> installation/uninstallation information. I unzipped the contents of >> WinGhci-1.0-bin.zip into the "C:\Documents and Settings\<username>\My >> Documents\" folder, but there was no README file. >> >> > And version information - I tried it with GHC 6.4 and it died (Not > Responding) > > What version of GHCi does it require? > > And no, I won't upgrade GHC just yet (this is the latest GHC/wxHaskell > combo that works for me with GHCi...) > >> >> >> > I have tested it with GHC 6.10.1. The latest GHC version that I have currently installed is GHC 6.6, and it seems to work too. Do you have GHC bin directory on your path? > > -- > -------------------------------------------------------------------- > Andrew Butterfield Tel: +353-1-896-2517 Fax: +353-1-677-2204 > Foundations and Methods Research Group Director. > School of Computer Science and Statistics, > Room F.13, O'Reilly Institute, Trinity College, University of Dublin > http://www.cs.tcd.ie/Andrew.Butterfield/ > -------------------------------------------------------------------- > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Fwd: [Haskell-cafe] Re: ANNOUNCE: WinGhci, a GUI for GHCI on Windows
by Pepe Gallardo 26 Mar '09

26 Mar '09

---------- Forwarded message ---------- From: Pepe Gallardo <pepe.haskell(a)gmail.com> Date: 2009/3/25 Subject: Re: [Haskell-cafe] Re: ANNOUNCE: WinGhci, a GUI for GHCI on Windows To: "Benjamin L.Russell" <DekuDekuplex(a)yahoo.com> Hi Benjamin*,* ** The only requirement to run WinGhci is to have GHC installed and to have GHC bin directory on your path. The way to start the application is by executing winghci.exe. Install.exe is an small program that associates .hs files with WinGhci (it should be run from the same directory where WinGhci is installed). Note that this association is optional. I have added a wiki page on this. 2009/3/23 Benjamin L.Russell <DekuDekuplex(a)yahoo.com> > Just another couple of thoughts for possible additional improvement: > > 1. It would be even nicer if WinGhci added a menu entry to the > "Start" menu automatically, as WinHugs does. > > 2. For the proposed menu entry, it would also probably be a good idea > if WinGhci added a folder for that menu entry, and included a link to > a "README" file in there, as WinHugs does also. > > 3. In order to distinguish WinGhci from GHCi, it might also be > helpful if WinGhci had a different icon; the current WinGhci icon is > identical to the one for GHCi (perhaps use the forthcoming official > Haskell logo here?). > WinGhci icon is different (although quite similar) from GHCi icon, at least for medium to large icon sizes. > > Just my two cents for now.... > > -- Benjamin L. Russell > -- > Benjamin L. Russell / DekuDekuplex at Yahoo dot com > http://dekudekuplex.wordpress.com/ > Translator/Interpreter / Mobile: +011 81 80-3603-6725 > "Furuike ya, kawazu tobikomu mizu no oto." > -- Matsuo Basho^ > > _______________________________________________ > Haskell-Cafe mailing list > Haskell <Haskell-Cafe(a)haskell.org>-Cafe(a)haskell.org<Haskell-Cafe(a)haskell.org> > http://www.haskell.org/mailman/listinfo/haskell-cafe > <Haskell-Cafe(a)haskell.org> >

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a cabal package with both a library and executable programs
by Manlio Perillo 26 Mar '09

26 Mar '09

Hi. This example is taken from the Cabal documentation: Name: TestPackage ... Library Build-Depends: HUnit Exposed-Modules: A, B, C Executable program1 Main-Is: Main.hs Hs-Source-Dirs: prog1 Other-Modules: A, B Executable program2 Main-Is: Main.hs Hs-Source-Dirs: prog2 Other-Modules: A, C, Utils Here I see a small problem. Why should I explicitly declare modules from the library that are used in the executables? I would like to do, instead ... Executable program1 Main-Is: Main.hs Hs-Source-Dirs: prog1 build-depends: TestPackage Executable program2 Main-Is: Main.hs Hs-Source-Dirs: prog2 build-depends: TestPackag Other-Modules: Utils I tried this, but configuration fails, since Cabal does not find the TestPackage. It is true that it does not yet exists, but we are going to build it! Should I fill a feature request ticket, or this is how it is supposed to work? Thanks Manlio

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Learning Haskell
by Tom.Amundsen 25 Mar '09

25 Mar '09

How long did it take you to become proficient in Haskell? By that, I mean - how long until you were just as comfortable with Haskell as you were with your strongest language at that time? -- View this message in context: http://www.nabble.com/Learning-Haskell-tp22673552p22673552.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Re: How to increment an Int in Haskell (stack overflow issue)
by John Lato 25 Mar '09

25 Mar '09

> From: Tim Bauer <bauertim(a)eecs.orst.edu> > > I have a program that is currently blowing out the stack, > Stack space overflow: current size 8388608 bytes. > Use `+RTS -Ksize' to increase it. > I am pretty sure I get to the end of the computation that > increments various statistic counters (lazily?) and only > when I go to print them out at the end, do things fail. > In addition to the excellent advice provided by others on this topic, you may want to look at using GHC's heap profiler if you can't track down the source of a memory issue. I've found it helpful in the past. Keep in mind that there are several different modes that may or may not be helpful for a particular problem, so you should try them all to see if you get any useful information. John

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Data Structures with Haskell
by Rohit Agrawalla 25 Mar '09

25 Mar '09

I am a beginner haskell programmer. I am interested in data structures implementation (all from basic ones like stack, queues etc. to advance ones like balanced binary trees, graphs etc.) in haskell. It would be really helpful if someone can point some good references for the same. Regards , Rohit

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ANNOUNCE: WinGhci, a GUI for GHCI on Windows
by Pepe Gallardo 25 Mar '09

25 Mar '09

Hi, I am pleased to announce the first release of WinGhci. WinGhci is a simple GUI for GHCI on Windows. It is closely based on WinHugs, and provides similar functionality. WinGhci project web page: http://code.google.com/p/winghci/<mhtml:{5097F7F7-AA40-4661-A7CF-D5EEC38F084A}mid://00000003/!x-usc:http://co…> Binaries: http://winghci.googlecode.com/files/WinGhci-1.0-bin.zip<mhtml:{5097F7F7-AA40-4661-A7CF-D5EEC38F084A}mid://00000003/!x-usc:http://wi…> Sources: http://winghci.googlecode.com/files/WinGhci-1.0-src.zip<mhtml:{5097F7F7-AA40-4661-A7CF-D5EEC38F084A}mid://00000003/!x-usc:http://wi…> Acknowledgements Much of the code in WinGhci was taken from the Winhugs project. Many thanks to Neil Mitchell for giving us permission to use his code. <mhtml:{5097F7F7-AA40-4661-A7CF-D5EEC38F084A}mid://00000003/!x-usc:http://wi…> Pepe Gallardo

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