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[Announcement] Fedora 12 rpms for leksah 0.8.0.1 now available
by Lakshmi Narasimhan 18 Mar '10

18 Mar '10

Leksah - 0.8.0.1 rpms for Fedora 12 now available http://leksah.org/download.html About Leksah: *Leksah* is the Haskell IDE of choice. It is written in Haskell, uses Gtk, and runs on Linux, Windows and Mac OS X. Leksah is a practical tool to support the Haskell development process. It requires the Glasgow Haskell Compiler (GHC). *Installation Instructions * *Procedure for x86 platform* Before proceeding to install the leksah rpms, Uninstall leksah-0.6.1, ghc-binary-devel packages, incase you have installed them from the leksah download page. Use the following command yum remove leksah ghc-binary-devel Install these dependencies from the following location http://leksah.org/packages/dependencies-0.8.0.1.fc12.i386.tar.gz Extract the rpms from the tar.gz file. Select the rpms, right click and click Install. To install from command line, change into the extracted directory, become superuser and type in this command for x86 yum --nogpgcheck install ghc-binary-devel-0.5.0.2-1.fc12.i386.rpm ghc-deepseq-devel-1.1.0.0-1.fc12.i386.rpm ghc-ltk-devel-0.8-1.fc12.i386.rpm ghc-binary-shared-devel-0.8-1.fc12.i386.rpm ghc-hslogger-devel-1.0.10-1.fc12.i386.rpm haddock-leksah-2.5.0-1.fc12.i386.rpm Download the leksah rpms from this location http://leksah.org/packages/leksah-0.8.0.1-1.fc12.i386.rpm http://leksah.org/packages/leksah-server-0.8.0.1-1.fc12.i386.rpm Use the same procedure used for installing the dependencies. * Procedure for x86_64 platform* Before proceeding to install the leksah rpms, please install these dependencies from the following location http://leksah.org/packages/dependencies-0.8.0.1.fc12.x86_64.tar.gz Extract the rpms from the tar.gz file. Select the rpms, right click and click Install. To install from command line, change into the extracted directory, become superuser and type in this command yum --nogpgcheck install ghc-binary-devel-0.5.0.2-1.fc12.x86_64.rpm ghc-hslogger-devel-1.0.10-1.fc12.x86_64.rpm ghc-binary-shared-devel-0.8-1.fc12.x86_64.rpm ghc-ltk-devel-0.8-1.fc12.x86_64.rpm ghc-deepseq-devel-1.1.0.0-1.fc12.x86_64.rpm haddock-leksah-2.5.0-1.fc12.x86_64.rpm Download leksah rpms from this location http://leksah.org/packages/leksah-0.8.0.1-1.fc12.x86_64.rpm http://leksah.org/packages/leksah-server-0.8.0.1-1.fc12.x86_64.rpm Use the same procedure used for installing the dependencies *Running leksah *Once installation is completed, leksah menu item appears under Applications->Programming (in GNOME). -- Regards Lakshmi Narasimhan T V

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Strange error during compilation/linking
by Erik Quaeghebeur 18 Mar '10

18 Mar '10

Hi, I get the following error while compiling (I guess it's actually the linking step): $ghc -o cmimc cmimc.hs cmimc.o: In function `rP1_info': (.text+0x32a): undefined reference to `containerszm0zi2zi0zi1_DataziMap_zdf2_closure' cmimc.o: In function `rP3_info': (.text+0x396): undefined reference to `containerszm0zi2zi0zi1_DataziMap_zdf2_closure' cmimc.o: In function `rPh_info': (.text+0x666): undefined reference to `containerszm0zi2zi0zi1_DataziMap_fromList_closure' cmimc.o: In function `rPj_info': (.text+0x6ca): undefined reference to `containerszm0zi2zi0zi1_DataziMap_fromList_closure' cmimc.o: In function `sR5_info': (.text+0x1225): undefined reference to `__stginit_containerszm0zi2zi0zi1_DataziMap_' cmimc.o: In function `rP1_srt': (.data+0x90): undefined reference to `containerszm0zi2zi0zi1_DataziMap_zdf2_closure' cmimc.o: In function `rP3_srt': (.data+0xac): undefined reference to `containerszm0zi2zi0zi1_DataziMap_zdf2_closure' cmimc.o: In function `rPh_srt': (.data+0x15c): undefined reference to `containerszm0zi2zi0zi1_DataziMap_fromList_closure' cmimc.o: In function `rPj_srt': (.data+0x174): undefined reference to `containerszm0zi2zi0zi1_DataziMap_fromList_closure' collect2: ld returned 1 exit status However, running the program with ghci: $ghci cmimc.hs Prelude Main> :set args "testinput.txt" Prelude Main> :trace main gives the correct output... Where might there be a problem? In my installation (Kubuntu i386, ghc6.10.4-1ubunbtu2) perhaps? Please tell me if/which additional info I need to provide. TIA, Erik

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Defining 'words' in terms of 'span'
by Roger Whittaker 18 Mar '10

18 Mar '10

I found some exam papers linked from this page: http://www.cs.chalmers.se/Cs/Grundutb/Kurser/d1pt/d1pta/external.html And I have been trying some questions from them. I'm currently baffled by question 2(b) on this one: http://www.cs.chalmers.se/Cs/Grundutb/Kurser/d1pt/d1pta/tenta2000-04.ps A word is a sequence of alphabetic characters, which you can recognise using the standard function isAlpha :: Char -> Bool Using span, define a function words :: String -> [String] which finds a list of the words occurring in a string. For example, words "Now is the winter of our discontent!" == ["Now","is","the","winter","of","our","discontent"] words "2+3" == [] words "1 by 1" == ["by"] Can anyone give me a clue how to start? -- ======================== Roger Whittaker roger(a)disruptive.org.uk http://disruptive.org.uk ========================

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about installation of Haskell
by love_pku 17 Mar '10

17 Mar '10

Dear Sir or Madam:: Sorry to trouble you! I am a beginner of Haskell and I just run into problems to install it. So I hope if you can tell me which version of Haskell should I use for Ubuntu 8.04 operating system.. Thank you very much! Best wishes, Yours juan

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generating by mapping
by Szilveszter Juhos 17 Mar '10

17 Mar '10

Hi, I have something like: data Stuff = Stuff { aNum :: Int , anStr :: String } deriving (Show) let first = Stuff 123 "qwe" let second = Stuff 321 "asd" print first print second and works fine. What is the right "map" statement if I want to generate these stuff using lists like: let strs = [ "qwe", "asd", "zxc" ] let nums = [ 123, 321, 345] ? Cheers: Szilva

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Reading in the contents of a variable number of files
by Tim Perry 17 Mar '10

17 Mar '10

I need to read in and then combine a variable number of files. I am trying to figure out how to get the contents of all the files into an array. let fileContentsArray = getData ["dataFile1.txt", "dataFile2.txt"] getData :: [String] -> [String] getData [] = [] getData (f:files) = do fileData <- readFile f fileData : (getData files) I figured I could use readFile to open the files. But, I need to use <- to get the data out of the IO Action and into a value. I thought I could write a function like the following, but I'm getting no-where. I suspect I'm missing something basic about IO in Haskell. Can anybody point me to a good resource.... Thanks, Tim

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Parsec 3.0
by Tim Perry 16 Mar '10

16 Mar '10

When I install Parsec using Cabal, I get version 2.1.0.1. Is there a way to get version 3.1? Or do I have to build it by hand? Thanks, Tim C:\Documents and Settings\perry\haskell>cabal upgrade parsec --reinstall Resolving dependencies... Configuring parsec-2.1.0.1... Preprocessing library parsec-2.1.0.1... Building parsec-2.1.0.1... ....

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Struct-like syntax issues
by Sergey Mironov 15 Mar '10

15 Mar '10

Hi. I have definitions like data MyData = MyData { a :: A, b :: B, c :: C, d :: D, ... z :: Z } makeMyData :: A -> B -> MyData makeMyData a' b' = MyData { a = a', b = b', c = default_c, ... z = default_z } The goal is to use it like myData1 = set_x x' . set_m m' . set_c c' $ makeMyData my_a my_b myData2 = set_z z' . $ makeMyData my_a my_b But. Writing set_* functions is a problem - MyData is loong and things like set_d :: D -> MyData -> MyData set_d val struct = struct{d=val} will form that boilerplate. Is there any _right_ way of doing it? myData3 = (makeMyData my_a my_b) {x=x', z=z'} approach is not working.. -- Thanks, Sergey

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Randomly selecting a data constructor
by Evgenij Merenkov 14 Mar '10

14 Mar '10

Hello. I have the following data and it's constructors: FigType = TR1 | TR2 | TR3 | TR4 | SQ | L1 | L2 | Z1 | Z2 | Z3 | Z4 | NoFigure I need to randomly return one of them in a function. The obvious solution to me, is simply using a random number generator and case statement, where each value generated is associated with each data constructor. Like this: import System.Random randomFigType :: IO FigType randomFigure = do x <- randomRIO (1::Int,11::Int) return $ case x of 1 -> TR1 2 -> TR2 3 -> TR3 e t.c. But is there a more direct way to do this? _________________________________________________________________ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. https://signup.live.com/signup.aspx?id=60969

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homogeneous value list
by Luca Ciciriello 14 Mar '10

14 Mar '10

Hi. I know, this is a very basic question but I've had some trouble with it. I've a list and I want to write a function isHomogeneous :: [String] -> Bool returning True is all the elements of the list are equals and False otherwise. In my first ugly test I've used a list-comprehension method, but I'm sure that exists a more elegant/short way to obtain the same result. Thanks in advance for any answer. Luca _________________________________________________________________ Tell us your greatest, weirdest and funniest Hotmail stories http://clk.atdmt.com/UKM/go/195013117/direct/01/

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