- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Ideas
by Andrew Coppin 26 Aug '07

26 Aug '07

Iain Lane wrote: >> - Blogging software. (Because there isn't enough of it in the world yet.) >> > > In addition (because a little competition can't help ;), I'm going to > be experimenting with writing a blog engine for my final year project > at Uni next year - 2007/08. Hopefully some good will come of it, i.e. > something that people (I) can actually use. It'll probably be more > blog less CMS than Hope. At the minute I'm looking at using HAppS for > most of it. Should be fun! > Good luck with that - should be enjoyable at least. ;-) I'm going to have a go at it myself as well. My current blog uses something called "word press", and I don't like it especially much. (It *insists* on chewing up all my carefully applied formatting. And the people providing it have locked it down so there's loads I can't change...) So I'm hoping to write something nice to replace it with. But we'll see...

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Re: [Haskell-cafe] Ideas
by Andrew Coppin 26 Aug '07

26 Aug '07

Bertram Felgenhauer wrote: > Hi, > > You wrote: > >> - An interactive function plotter. (GNUplot is nice, but it can't plot >> recursive functions...) >> > > Actually you can express a lot of those with the ?: operator. > Ooo... interesting. I don't recall seeing *that* in the manual! > gnuplot> f(x) = x < 1 ? 0 : f(x/2) + 1 > gnuplot> plot f(x) > > works just as expected. Mutually recursive functions defined that > way work, too. > > Still, support could be a lot better here. > OK... so how do I plot a graph of the Fibonacci numbers? Similarly, how do I plot (what Haskell calls) interate f 0?

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newbie - how to call a Haskell interpreter from C
by Brock Peabody 26 Aug '07

26 Aug '07

Hi, I've been trying to find place to use Haskell at work, and I think a good opportunity will be to use it for our scripting language. To do that, I need to be able to invoke an interpreter directly from another language. I've investigated using HaskellScript (too web/ActiveX centric), but really I just want to compile ghci or hugs into my executable/library. It seems like this is something I should be able to figure out easily, but so far I've failed and have not found any reference to others succeeding. any advice? thanks in advance, Brock

3 3

Question of a manual computation on Reader Monad.
by Peter Cai 25 Aug '07

25 Aug '07

Hi all, In order to improve my understanding of monad, I am trying to do some manual computation on "Reader Monad" but I got some problem. The computation is like this: --instance Monad (Reader e) where -- return a = Reader $ \e -> a -- (Reader r) >>= f = Reader $ \e -> f (r e) e runReader (do { b <- Reader $ show; return b } ) -- This is the initial expression, it should equals "show" runReader (Reader $ show >>= \b -> return b) -- remove do notion runReader (Reader $ \e -> return( show e ) e) -- apply the definition of ">>=" runReader (Reader $ \e -> (Reader $ \e1 -> show(e)) e) -- apply the definition of "return" But the last expression is incorrect, and I don't know how to go on. Could anyone explain this for me? Thanks in advance! Reference : http://www.haskell.org/all_about_monads/html/readermonad.html

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RE: [Haskell-cafe] How to fix linker errors when creating a package using cabal
by Peter Verswyvelen 25 Aug '07

25 Aug '07

Indeed, adding the non-exposed modules to the other-modules fixed it. Thanks Allan! Cheers, Peter -----Original Message----- From: Allan Clark [mailto:a.d.clark@ed.ac.uk] Sent: Saturday, August 25, 2007 2:28 PM To: Peter Verswyvelen Subject: Re: [Haskell-cafe] How to fix linker errors when creating a package using cabal Peter Verswyvelen wrote: > I'm trying to make a package of Ben.Lippmeier's very nice ANUPlot graphics > library (http://cs.anu.edu.au/people/Ben.Lippmeier) > > IMHO this would be a great contribution to the Haskell library, it's very > clean code for newbies :) > > I created the following cabal file: > > name: Plot > version: 1.1 > license: AllRightsReserved > maintainer: Ben.Lippmeier(a)anu.edu.au > exposed-modules: > Graphics.Plot.Display, > Graphics.Plot.Picture, > Graphics.Plot.Primitive, > Graphics.Plot.Render, > Graphics.Plot.Colors, > Graphics.Plot.Util, > Graphics.Plot.RenderState, > Graphics.Plot.Animate, > Graphics.Plot.View, > Graphics.Plot.Wrapper, > Graphics.Plot > Build-Depends: base, OpenGL, GLUT > ghc-options: -fglasgow-exts > > and then tried > runhaskell Setup.hs configure > runhaskell Setup.hs build > runhaskell Setup.hs install > > which all seemed to work fine (see log below). > > However, when building an example that uses that package, I get a lot of > linker errors (see log below) > > Is this because I configured the cabal files incorrectly, or do I have to > adjust the module sources so they explicitly export the missing symbols? > > Thanks, > Peter > [ snip ] > Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0x2f1):fak > e: undefined reference to > `Plotzm1zi1_GraphicsziPlotziCallback_Display_con_info' > Hi, I'm not cabal expert, but basically I had a similar problem, and I fixed it by adding a missing module in the 'exposed-modules' part. Basically where is con_info defined, it's probably in a module which isn't exposed. If so then either put it in the 'exposed-modules' section or if you do not wish to expose it then maybe you could try putting it in a 'other-modules' section. regards allan

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Haskellnet could not find network-any dependency.
by Edward Ing 25 Aug '07

25 Aug '07

Hi, I am trying to install Haskellnet. But the configuration breaks on dependency of network-any in GHC 6.6. I thought network-any was part of Hierarchical libraries? If not where do I get it? Edaward.

2 1

How to fix linker errors when creating a package using cabal
by Peter Verswyvelen 25 Aug '07

25 Aug '07

I'm trying to make a package of Ben.Lippmeier's very nice ANUPlot graphics library (http://cs.anu.edu.au/people/Ben.Lippmeier) IMHO this would be a great contribution to the Haskell library, it's very clean code for newbies :) I created the following cabal file: name: Plot version: 1.1 license: AllRightsReserved maintainer: Ben.Lippmeier(a)anu.edu.au exposed-modules: Graphics.Plot.Display, Graphics.Plot.Picture, Graphics.Plot.Primitive, Graphics.Plot.Render, Graphics.Plot.Colors, Graphics.Plot.Util, Graphics.Plot.RenderState, Graphics.Plot.Animate, Graphics.Plot.View, Graphics.Plot.Wrapper, Graphics.Plot Build-Depends: base, OpenGL, GLUT ghc-options: -fglasgow-exts and then tried runhaskell Setup.hs configure runhaskell Setup.hs build runhaskell Setup.hs install which all seemed to work fine (see log below). However, when building an example that uses that package, I get a lot of linker errors (see log below) Is this because I configured the cabal files incorrectly, or do I have to adjust the module sources so they explicitly export the missing symbols? Thanks, Peter ------------------ LOG ------------------------------- L:\3rdParty\ANUPlot\src>runhaskell Setup.hs unregister Unregistering Plot-1.1... Saving old package config file... done. Writing new package config file... done. L:\3rdParty\ANUPlot\src>runhaskell Setup.hs clean cleaning... L:\3rdParty\ANUPlot\src>runhaskell Setup.hs configure --global Configuring Plot-1.1... configure: Dependency base-any: using base-2.1.1 configure: Dependency OpenGL-any: using OpenGL-2.2.1 configure: Dependency GLUT-any: using GLUT-2.1.1 configure: Using install prefix: C:\Program Files configure: Binaries installed in: C:\Program Files\Haskell\bin configure: Libraries installed in: C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1 configure: Private binaries installed in: C:\Program Files\Plot-1.1 configure: Data files installed in: C:\Program Files\Common Files\Plot-1.1 configure: Using compiler: c:\app\ghc\bin\ghc.exe configure: Compiler flavor: GHC configure: Compiler version: 6.6.1 configure: Using package tool: c:\app\ghc\bin\ghc-pkg.exe configure: Using ar found on system at: c:\app\ghc\bin\ar.exe configure: No haddock found configure: No pfesetup found configure: No ranlib found configure: Using runghc found on system at: c:\app\ghc\bin\runghc.exe configure: No runhugs found configure: No happy found configure: No alex found configure: Using hsc2hs: c:\app\ghc\bin\hsc2hs.exe configure: No c2hs found configure: No cpphs found configure: No greencard found L:\3rdParty\ANUPlot\src>runhaskell Setup.hs build Preprocessing library Plot-1.1... Building Plot-1.1... L:\3rdParty\ANUPlot\src>runhaskell Setup.hs register Registering Plot-1.1... Reading package info from ".installed-pkg-config" ... done. Saving old package config file... done. Writing new package config file... done. L:\3rdParty\ANUPlot\src>runhaskell Setup.hs install Installing: C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1 & C:\Program Files\Haskell\bin Plot-1.1... Registering Plot-1.1... Reading package info from ".installed-pkg-config" ... done. Saving old package config file... done. Writing new package config file... done. Linking AnimClock.exe ... C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0x2f1):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Display_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0xc7c):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0xdcb):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Idle_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0xdfc):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Display_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0xe3b):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Display_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.text+0xe68):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Display_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Wrapper.o)(.rodata+0x54):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.text+0x3d6) :fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.text+0x652) :fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.text+0x8ce) :fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.text+0xb4a) :fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.text+0xdc8) :fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_KeyMouse_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(RenderState.o)(.rodata+0x10 ):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x190b):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x19cc):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x1b9b):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x1c5c):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x20c9):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x21fc):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x22f0):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x2400):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x2e83):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x2f74):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x305c):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x37f9):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x3954):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x3a60):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x3b88):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x3dec):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x3ebc):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x402a):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x43c1):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x45f2):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x4975):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x4c5a):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x4efe):fake: more undefined references to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' follow C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x5b0a):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Reshape_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x5b38):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_Motion_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.text+0x5b65):fake: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_KeyMouse_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x130):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x134):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x144):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x148):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x170):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x174):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x1a4):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(View.o)(.rodata+0x1a8):fake : undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Render.o)(.text+0x1e2b):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziTexture_cacheTexture_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Render.o)(.text+0x2146):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziRaster_withRasterCoords_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Render.o)(.text+0x2484):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziRaster_withRasterCoords_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Render.o)(.rodata+0xc0):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziRaster_withRasterCoords_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Render.o)(.rodata+0xc4):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziTexture_cacheTexture_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x322):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x511):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x75c):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x838):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x908):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x1111):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x1220):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x151a):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x16bc):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziCallback_KeyMouse_con_info' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x17bd):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x18b4):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.text+0x1a24):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.rodata+0x28):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.rodata+0x2c):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.rodata+0x98):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.rodata+0xac):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zhzh_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Animate.o)(.rodata+0xb0):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziUtilOp_zlzhzhzg_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.text+0x766):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpFragmentState_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.text+0x76d):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpFramebufferState_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.text+0x7d7):fak e: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpGlutState_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.rodata+0xa4):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpGlutState_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.rodata+0xa8):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpFramebufferState_closure' C:\Program Files\Haskell\Plot-1.1\ghc-6.6.1/libHSPlot-1.1.a(Display.o)(.rodata+0xac):fa ke: undefined reference to `Plotzm1zi1_GraphicsziPlotziDump_dumpFragmentState_closure' collect2: ld returned 1 exit status

2 2

Remember the future
by Andrew Coppin 25 Aug '07

25 Aug '07

I've seen comments in various places that monads allow you to "borrow things from the future". That sounds completely absurd to me... can anybody explain?

8 12

Re: [Haskell-cafe] Style
by Marc A. Ziegert 25 Aug '07

25 Aug '07

whops... i did check it, but that was a copypaste mistake. buggy: > tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives > where fives = iterate (*5) 1 should be: > tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives > where fives = iterate (*5) 5 - marc Am Freitag, 24. August 2007 schrieben Sie: > Hi Marc > > First off, thanks for your reply. > >> tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives > >> where fives = iterate (*5) 1 > Did you check this one? IMHO I think it's producing the 'wrong' answer. > > *Main> tm_parallelizable_v1 100 > 124 > (0.00 secs, 0 bytes) > > *Main> tm 100 > 24 > (0.00 secs, 0 bytes) > > If comparing the result to the other variants is accepted as a sort > of proof. ;-) > > But calculating the number of trailing zero's of n! is a matter of > counting powers of five in the factorized n!: f.e.: > > 10! = 1 2 3 2^2 5 2*3 7 2^3 3^2 2*5 > --> 5^2 --> picking up enough powers of 2 --> (2*5)^2 = 100 > > So you will have to correct your 'fives' to f.e. > > fives = tail $ iterate (*5) 1 > > > > Regards > > > @@i > > >

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Help using CGIT
by Rich Neswold 25 Aug '07

25 Aug '07

Hello! I've been having a tough time trying to use the CGI monad transformer (CGIT). Hopefully someone can show me my misstep(s). I have a CGI script that's evolving. Early on, it needed a single database access. Now it's doing two accesses (and it looks like I'll be adding more.) Rather than making a connection for each access, the script needs to connect once. To do this, I want to combine the CGI monad with the Reader monad. This version compiles cleanly: > module AppMonad (App (..), runApp) > where > > import Control.Exception (bracket) > import Control.Monad.Reader > import Network.CGI.Monad > import Network.CGI.Protocol > import System.IO (stdin, stdout) > import Database.HSQL.PostgreSQL > > newtype App a = App (ReaderT Connection (CGIT IO) a) > deriving (Monad, MonadIO, MonadReader Connection) > > runApp :: App CGIResult -> IO () > runApp (App a) = > bracket (connect "host" "dbname" "user" "password") > disconnect > (\c -> do { env <- getCGIVars > ; hRunCGI env stdin stdout (runCGIT (runReaderT a c)) > ; return () } ) Unfortunately, when another module tries to actually use the monad, I get warnings about "No instance for (MonadCGI App)". I tried making an instance: > instance MonadCGI App where > cgiAddHeader = ? > cgiGet = ? But I don't know how to define these functions. I tried various 'lift'ing combinations, but couldn't come up with a solution that would compile. I'm also disappointed that I had to break apart 'runCGI' (by cut-and-pasting its source) because I couldn't make it believe my monad looked enough like MonadCGI. My previous experiment with monad transformers was successful. It didn't use CGIT, however, so the 'run*' functions were simpler. Does anyone have an example of using CGIT (I didn't find any from Google)? Shouldn't I be able to use 'runCGI' with my monad? CGIT users shouldn't be required to re-implement 'runCGI", right? Any help or ideas is appreciated! -- Rich JID: rich(a)neswold.homeunix.net AIM: rnezzy

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