February 2009 - Haskell-Cafe

Question re: denotational semantics in SPJ's "Implementation of FPLs" book
by Devin Mullins 01 Feb '09

01 Feb '09

I'm reading SPJ's "The Implementation of Functional Programming Languages," and on page 32, it defines the multiplication operator in its extended lambda calculus as: Eval[[ * ]] a b = a x b Eval[[ * ]] _|_ b = _|_ Eval[[ * ]] a _|_ = _|_ Is that complete? What are the denotational semantics of * applied to things not in the domain of the multiplication operator x, such as TRUE (in the extended lambda defined by this book) and functions (in normal lambda calc)? Do these things just eval to bottom? Or is this just to be ignored, since the extended calculus will only be applied to properly "typed" expressions in the context of this book?

2 1

Takusen 0.8.3 install problems
by Praki Prakash 01 Feb '09

01 Feb '09

I am trying to install Takusen 0.8.3 with ghc 6.10.1 on Ubuntu 8.04 (same issue on Win XP as well). I get the following complaint from cabal. Module `Distribution.PackageDescription' does not export `writeHookedBuildInfo' cabal: Error: some packages failed to install: Takusen-0.8.3 failed during the configure step. The exception was: exit: ExitFailure 1 Any suggestions on how to fix this issue? Thanks, Praki

4 6

Howto debug erros occuring just by linking to non-Haskell libraries
by Mads Lindstrøm 01 Feb '09

01 Feb '09

Hi Haskeleers I am trying to track down the cause of an error occurring in the Linux version of wxHaskell. The error occurs before the main function is executed. That is, it occurs if one imports the wxHaskell libraries, and it occurs even if one do not execute any wxHaskell function. Specifically, GLib complains that a initialization-function has not been called. My guess is, that it has something to do with the wxWidgets (and gtk or glib) libraries wxHaskell links to. Some people have suggested it may be an error in the way GHC links with C libraries. But that is all guesswork, I would need something more solid if I were to file GHC bugreport. Here is a simple Haskell program to illustrate the problem: module Main where import Graphics.UI.WX main = print "sdfjkl" and when we compile and execute this program we get: (process:13986): GLib-GObject-CRITICAL **: gtype.c:2240: initialization assertion failed, use IA__g_type_init() prior to this function (process:13986): Gdk-CRITICAL **: gdk_cursor_new_for_display: assertion `GDK_IS_DISPLAY (display)' failed (process:13986): GLib-GObject-CRITICAL **: gtype.c:2240: initialization assertion failed, use IA__g_type_init() prior to this function (process:13986): Gdk-CRITICAL **: gdk_cursor_new_for_display: assertion `GDK_IS_DISPLAY (display)' failed "sdfjkl" So even if I do not call any wxHaskell functions, just by linking to wxHaskell, I get these errors. As Jeroen Janssen reports here http://www.mail-archive.com/wxhaskell-users@lists.sourceforge.net/msg00540.… , he is experiencing the same error, but his wxPython programs works. Thus, wxHaskell (or GHC or ...) must do something different. Could this error be related to the order which external libraries are loaded in? If so, do anybody know how to specify the load order? Can anybody help med with a good approach for debugging this error? Greetings, Mads Lindstrøm

1 0

Panic with GTK2HS 0.10.0 RC under Vista with GHCi 6.10.1; GHCi or GTK bug?
by Peter Verswyvelen 01 Feb '09

01 Feb '09

Often when trying to run my GTK2HS application the first time with GHCi I get : panic! (the 'impossible' happened) (GHC version 6.10.1 for i386-unknown-mingw32): loadObj: failed Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug This only occurs when I forgot to set my current directory correctly; then GHCi gives an error since it can't find modules GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Boxes.hs:23:17: Could not find module `NM8.GUI.Layout': Use -v to see a list of the files searched for. Failed, modules loaded: none. If I then correctly set my current directory using the :cd command, and try again, I get the panic crash. When I start GHCi again and immediately set the correct current directory, it works fine. I haven't tried to isolate the problem, but maybe others have experienced this problem? It's not really a show-stopper, just but a bit annoying

1 0

ANN: regex-xmlschema
by Uwe Schmidt 01 Feb '09

01 Feb '09

I'm pleased to announce (yet another) package for processing text with regular expressions: regex-xmlschema The W3C XML Schema specification (http://www.w3.org/TR/xmlschema11-2/#regexs) defines a language for regular expressions. This language is used in the XML Schema spec when defining the data type library part. This regex-xmlschema package contains a complete implementation of this spec. It is implemented with the technique of derivations of regular expression. Main features are: * full support of Unicode including all Unicode code blocks and character properties * a purely functional interface * 100% Haskell, no other packages except parsec needed * cabal build file * extensions for intersection, set difference, exclusive or and interleave of regular sets (regular expressions), * extensions for subexpression matches * functions for matching, for grep like searching, for stream like editing (sed like) and for tokenizing. With this package, it becomes rather easy to build lightweight tokenizers e.g. for colourizing arbitrary programming languages, like hscolor does it for Haskell. The package is available from Hackage: "http://hackage.haskell.org/cgi-bin/hackage-scripts/package/regex-xmlschema", there's a darcs repo for the latest source: "http://darcs2.fh-wedel.de/hxt/regex/" and a wiki page, describing the extension and giving some examples for using the library: "http://www.haskell.org/haskellwiki/Regular_expressions_for_XML_Schema" Cheers, Uwe -- Uwe Schmidt FH Wedel http://www.fh-wedel.de/~si/

1 0

can't build testpack
by Ezekiel Smithburg 31 Jan '09

31 Jan '09

this is the error message i get: ezekiel-smithburgs-macbook-pro-15% runhaskell Setup.* build Preprocessing library testpack-1.0.0... Building testpack-1.0.0... [1 of 3] Compiling Test.QuickCheck.Instances ( src/Test/QuickCheck/Instances.hs, dist/build/Test/QuickCheck/Instances.o ) [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, dist/build/Test/QuickCheck/Tools.o ) [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, dist/build/Test/HUnit/Tools.o ) src/Test/HUnit/Tools.hs:28:36: Class `Control.Exception.Exception' used as a type In the type `Control.Exception.Exception' In the type `Control.Exception.Exception -> IO a -> IO ()' In the type `String -> Control.Exception.Exception -> IO a -> IO ()' what should i do? need this in order to build hdbc 2.0, which i'm hoping solves a problem i was having earlier (memory leak).

3 8

Re: [Haskell-cafe] can't build testpack
by Ezekiel Smithburg 31 Jan '09

31 Jan '09

tried that version, it gets rid of that error message but now i have this one: ezekiel-smithburgs-macbook-pro-15% cabal --flag=split-base configure -p Configuring testpack-1.0.0... ezekiel-smithburgs-macbook-pro-15% cabal build Preprocessing library testpack-1.0.0... Building testpack-1.0.0... [1 of 3] Compiling Test.QuickCheck.Instances ( src/Test/QuickCheck/Instances.hs, dist/build/Test/QuickCheck/Instances.o ) [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, dist/build/Test/QuickCheck/Tools.o ) [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, dist/build/Test/HUnit/Tools.o ) src/Test/HUnit/Tools.hs:23:7: Could not find module `System.Random': Perhaps you haven't installed the profiling libraries for package random-1.0.0.1? Use -v to see a list of the files searched for. i'll start reading the cabal user guide and see if i can figure it out on my own, but i figure progress on this should be up on the list so if someone else has this problem, they can find this and solve it on their own. also, if someone else can figure it out before i do, that's cool too. thanks for your help so far! On Sat, Jan 31, 2009 at 8:14 PM, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: > Ok, sorry for the confusion, I should have checked it before: testpack > doesn't really need base-4, it needs base-3.The right dependency line is > (for both 6.10.1 and 6.8.3): > > Build-Depends: base >= 3 && < 4 , containers, random > > I really need to get some sleep... > > All best > > Christopher Skrzętnicki > > > On Sun, Feb 1, 2009 at 03:07, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: > >> Trying to follow Ezekiel's steps I bumped into this: >> >> >>> >> D:\biblioteki\testpack-1.0.0>cabal configure >> Configuring testpack-1.0.0... >> >> D:\biblioteki\testpack-1.0.0>cabal build >> Preprocessing library testpack-1.0.0... >> Building testpack-1.0.0... >> [1 of 3] Compiling Test.QuickCheck.Instances ( >> src\Test\QuickCheck\Instances.hs, dist\build\Test\QuickCheck\Instances.o ) >> [2 of 3] Compiling Test.QuickCheck.Tools ( src\Test\QuickCheck\Tools.hs, >> dist\build\Test\QuickCheck\Tools.o ) >> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >> dist\build\Test\HUnit\Tools.o ) >> >> src\Test\HUnit\Tools.hs:28:36: >> Class `Control.Exception.Exception' used as a type >> In the type `Control.Exception.Exception' >> In the type `Control.Exception.Exception -> IO a -> IO ()' >> In the type `String >> -> Control.Exception.Exception -> IO a -> IO ()' >> >> D:\biblioteki\testpack-1.0.0>cabal install >> Resolving dependencies... >> Configuring testpack-1.0.0... >> Preprocessing library testpack-1.0.0... >> Building testpack-1.0.0... >> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >> dist\build\Test\HUnit\Tools.o ) >> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.10.1 >> Registering testpack-1.0.0... >> Reading package info from "dist\\installed-pkg-config" ... done. >> Writing new package config file... done. >> <<< >> >> In short: "cabal configure && cabal build" fails, whereas "cabal install" >> builds fine. Looks like a bug in cabal-install. Am I right? >> >> All best >> >> Christopher Skrzętnicki >> >> >> >> On Sun, Feb 1, 2009 at 03:01, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: >> >>> testpack builds fine for me. In the original .cabal file there are >>> following lines: >>> >>> >>> >>> If flag(splitBase) >>> Build-Depends: base >= 3, containers, random >>> Else >>> Build-Depends: base < 3 >>> <<< >>> >>> Now that I think about it you didn't actually said what is your GHC >>> version. >>> Knowing that you can replace lines above with one line that matches your >>> specific configuration. >>> >>> GHC 6.8.3 : >>> Build-Depends: base >= 4, containers, random >>> GHC 6.10.1 : >>> Build-Depends: base >= 3, containers, random >>> >>> Please take care to restore and modify the original file. >>> >>> I think you should read Cabal user guide. This will save your time in the >>> future: >>> http://www.haskell.org/ghc/docs/latest/html/Cabal/index.html >>> >>> I *hope* those changes will fix your installation. I can't really test >>> it, because testpack build fine with my version of cabal: >>> >>> C:\Documents and Settings\Metharius>cabal install testpack --reinstall >>> Resolving dependencies... >>> 'testpack-1.0.0' is cached. >>> Configuring testpack-1.0.0... >>> Preprocessing library testpack-1.0.0... >>> Building testpack-1.0.0... >>> [1 of 3] Compiling Test.QuickCheck.Instances ( >>> src\Test\QuickCheck\Instances.hs, dist\build\Test\QuickCheck\Instances.o ) >>> [2 of 3] Compiling Test.QuickCheck.Tools ( src\Test\QuickCheck\Tools.hs, >>> dist\build\Test\QuickCheck\Tools.o ) >>> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >>> dist\build\Test\HUnit\Tools.o ) >>> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >>> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.10.1 >>> Registering testpack-1.0.0... >>> Reading package info from "dist\\installed-pkg-config" ... done. >>> Writing new package config file... done. >>> >>> C:\Documents and Settings\Metharius>cabal install -w >>> c:\ghc\ghc-6.8.3\bin\ghc testpack --reinstall >>> Resolving dependencies... >>> 'testpack-1.0.0' is cached. >>> Configuring testpack-1.0.0... >>> Preprocessing library testpack-1.0.0... >>> Building testpack-1.0.0... >>> [1 of 3] Compiling Test.QuickCheck.Instances ( >>> src/Test/QuickCheck/Instances.hs, dist\build/Test/QuickCheck/Instances.o ) >>> [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, >>> dist\build/Test/QuickCheck/Tools.o ) >>> [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, >>> dist\build/Test/HUnit/Tools.o ) >>> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >>> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.8.3 >>> Registering testpack-1.0.0... >>> Reading package info from "dist\\installed-pkg-config" ... done. >>> Saving old package config file... done. >>> Writing new package config file... done. >>> >>> Perhaps it may also be the difference of installing with "cabal install" >>> and "runhaskell Setup build". >>> >>> All best >>> >>> Christopher Skrzętnicki >>> >>> >>> 2009/2/1 Ezekiel Smithburg <tehgeekmeister(a)gmail.com> >>> >>>> oddly, when i do that, i'm back to the original error message. and >>>> sorry, i didn't understand what you meant, apparently. >>>> >>>> >>>> On Sat, Jan 31, 2009 at 7:41 PM, Krzysztof Skrzętnicki < >>>> gtener(a)gmail.com> wrote: >>>> >>>>> >>>>> 2009/2/1 Ezekiel Smithburg <tehgeekmeister(a)gmail.com> >>>>> >>>>>> solution to that problem: >>>>>> >>>>>> deleted the lines from "If flag(splitBase)" on and changed base in >>>>>> Build-Depends to base >= 4. >>>>>> >>>>> >>>>> Well, this is exactly what I suggested in the first place: >>>>> >>>>> > This error is due to usage of old base package in version 3.> In >>>>> .cabal file add dependency on base-4, in form "base >= 4". >>>>> >>>>> Regarding second qustion: >>>>> >>>>> > random 1.0.0.1 is installed, i've verified that. what does this >>>>> error mean? >>>>> >>>>> It means that .cabal file fails to specify dependancy on random >>>>> package. Add dependancy on "random" package next to "base>=4". This should >>>>> help. >>>>> >>>>> All best >>>>> >>>>> Christopher Skrzętnicki >>>>> >>>> >>>> >>> >> >

2 2