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AngloHaskell 2010
by Derek Wright 13 Jul '10

13 Jul '10

Are you interested in AngloHaskell 2010? AngloHaskell is a gathering of all people Haskell-related from beginners to seasoned hackers. Previously it has been held in Cambridge (three times) and London (once). Last year I volunteered to organise it but I want know when you can attend. Traditionally it is the first Friday and Saturday in August, which this year is the 6th and 7th August. But we may only have enough time to organise one day so the question for you is: Q) Which day is better for you? Friday, Saturday or either? I am looking for venues in London but if you can suggest or offer a venue then let me know. As well as attendees we are looking for talks on all and any Haskell related subjects. There is a section on the wiki page http://www.haskell.org/haskellwiki/AngloHaskell/2010 for talks. Please go ahead and add your talk to it. Let me know by email, the wiki or the #anglohaskell IRC channel. I planning to have the venue confirmed this week and then a full announcement will be made. Thanks, Derek.

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The site has been exploited (again)
by Christopher Done 13 Jul '10

13 Jul '10

http://haskell.org/ It says "TO BUY Cilamox ONLINE", etc. Whoever has power please fix this and upgrade the bloody wiki. This is ridiculous. Point the domain at tryhaskell.org or something. I'll put a holder page up. Anything. Cheers

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Marshalling
by Phyx 13 Jul '10

13 Jul '10

Hello I'm wondering if anyone ever benchmarked marshalling in Haskell/GHC. No matter how much I optimize my Haskell code my program still seems to run slow, which leads me to beleive that Marshalling is painfully slow. Does anyone know a way I can test this and fix it? Regards, Phyx

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ByteString, zipWith', and rewrite rules
by Thomas M. DuBuisson 13 Jul '10

13 Jul '10

Comments on the zipWith' function inside of Data.ByteString say: -- Rewrite rules -- are used to automatically covert zipWith into zipWith' when a pack is -- performed on the result of zipWith. This is only true internally to Data.ByteString because the zipWith' function could be inlined away by GHC once that module is compiled, right? If I want "pack (zipWith xor bs1 bs2)" to be efficient then I'll have to either get zipWith' exported or write my own lower level zipWith'? If I'm wrong here then the comment needs to be moved to somewhere that will get haddockized, perhaps with zipWith. Cheers, Thomas

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Functional dependencies and Peano numbers
by Oscar Finnsson 13 Jul '10

13 Jul '10

Hi, there is a lot of buzz around functional dependencies on the mailing list and Planet Haskell. I've read some of the tutorials and I think I understand how they work but I still haven't figured out where they can be useful. * Can someone give me a real world (preferably hackagedb) example where functional dependencies are used? * Can someone give me a real world (preferably hackagedb) example where Peano numbers a la "data Zero; data Succ n" are used? Finally... * All the examples involving functional dependencies are on the form > a b c | a b -> c but can they also be on a form similar to > a b c d e f g h| b c -> d e f | b d g -> h (i.e. d,e,f are decided by the b,c-combination while h is decided by the b,d,g-combination)? -- Oscar

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64-bit #const with hsc2hs?
by Dean Herington 13 Jul '10

13 Jul '10

Does anyone know if I can bring a 64-bit (long long or unsigned long long) value from C-land into Haskell via hsc2hs? #const on such a value seems to provide only the low 32 bits, at least in my environment (Haskell Platform 2009.2.0.2 on Windows). I've tried to create a 64-bit variant of #const without success. Dean

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PNG sample on haskellwiki
by C K Kashyap 13 Jul '10

13 Jul '10

Hi, I tried out the code on this page http://haskell.org/haskellwiki/Library/PNGbut the png file that'e emitted does not seem to open properly with image viewing tools. Has anyone tried it out? I added this bit for supplying the data for image creation - count=100 row = take count (cycle [True,False]) rows = take 100 (repeat row) image = png rows main=writeFile "hello.png" image -- Regards, Kashyap

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ghc-6.12 can't works with Cabal-1.8.0.4?
by Andy Stewart 13 Jul '10

13 Jul '10

Hi all, I upload package http://hackage.haskell.org/package/poppler-0.11.1 I can compile it on my box, but it build failure at hackage with below error: ------------------------------> error start <------------------------------ *** setup configure Reading installed packages... /usr/local/bin/ghc-pkg dump --global /usr/local/bin/ghc-pkg dump --user /usr/local/bin/ghc --print-libdir Creating setup (and its parents) /usr/local/bin/ghc -package Cabal-1.8.0.4 --make Setup.hs -o setup/setup -odir setup -hidir setup <command line>: cannot satisfy -package Cabal-1.8.0.4 (use -v for more information) *** Trying again with preferred-versions *** setup configure Reading installed packages... /usr/local/bin/ghc-pkg dump --global /usr/local/bin/ghc-pkg dump --user /usr/local/bin/ghc --print-libdir Creating setup (and its parents) /usr/local/bin/ghc -package Cabal-1.8.0.4 --make Setup.hs -o setup/setup -odir setup -hidir setup <command line>: cannot satisfy -package Cabal-1.8.0.4 (use -v for more information) ------------------------------> error end <------------------------------ My poppler.cabal is ------------------------------> poppler.cabal start <------------------------------ Name: poppler Version: 0.11.1 License: GPL-2 License-file: COPYING Copyright: (c) 2001-2010 The Gtk2Hs Team Author: Andy Stewart Maintainer: gtk2hs-users(a)sourceforge.net Build-Type: Custom Cabal-Version: >= 1.6 Stability: stable homepage: http://www.haskell.org/gtk2hs/ bug-reports: http://hackage.haskell.org/trac/gtk2hs/ Synopsis: Binding to the Poppler. Description: Poppler is a fork of the xpdf PDF viewer, to provide PDF rendering functionality as a shared library, to centralize the maintenance effort. And move to forward in a number of areas that don't fit within the goals of xpdf. Category: Graphics Tested-With: GHC == 6.12.3 Extra-Source-Files: Gtk2HsSetup.hs hierarchy.list template-hsc-gtk2hs.h x-Types-File: Graphics/UI/Gtk/Poppler/Types.chs x-Types-ModName: Graphics.UI.Gtk.Poppler.Types x-Types-Import: System.Glib.GObject x-Types-Lib: poppler x-Types-Prefix: poppler x-Types-Tag: poppler x-Types-Hierarchy: hierarchy.list Data-Dir: demo Data-Files: PdfViewer.hs Makefile Source-Repository head type: darcs location: http://patch-tag.com/r/AndyStewart/poppler Library build-depends: base >= 4 && < 5, array, containers, haskell98, mtl, bytestring, glib >= 0.11 && < 0.12, cairo >= 0.11 && < 0.12, gtk >= 0.11 && < 0.12 build-tools: gtk2hsC2hs, gtk2hsHookGenerator, gtk2hsTypeGen exposed-modules: Graphics.UI.Gtk.Poppler.Action Graphics.UI.Gtk.Poppler.Attachment Graphics.UI.Gtk.Poppler.Document Graphics.UI.Gtk.Poppler.FormField Graphics.UI.Gtk.Poppler.Layer Graphics.UI.Gtk.Poppler.Page Graphics.UI.Gtk.Poppler.Poppler other-modules: Graphics.UI.Gtk.Poppler.Enums Graphics.UI.Gtk.Poppler.Structs Graphics.UI.Gtk.Poppler.Types extensions: ForeignFunctionInterface include-dirs: . x-c2hs-Header: glib/poppler.h pkgconfig-depends: poppler-glib >= 0.12.4, gobject-2.0, glib-2.0, cairo >= 1.2.0, gdk-2.0, gdk-pixbuf-2.0, pango ------------------------------> poppler.cabal end <------------------------------ Something is wrong? Thanks, -- Andy

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haskell platform questions
by Warren Harris 12 Jul '10

12 Jul '10

I installed haskell platform some time ago, and now I'm wondering what version I have. How do I find out? Also, when the new one comes along on the 21st, is there a way to upgrade? Or if I must first uninstall the one I have now, how do I uninstall it? Is it recommended to periodically upgrade packages that came with the platform (cabal upgrade), or is it recommended that they be left alone to avoid dependency incompatibilities. Similar question for ghc itself -- can/should it be upgraded in the context of haskell platform? (I was hoping to try Leksah, but it dies without ghc 6.12.1. I seem to have 6.10.4.) Apologies in advance if this is all documented somewhere, but I couldn't find it on the haskell platform site/trac. BTW, I'm on Mac/ Leopard -- love the fact that it didn't take hours to build everything! Warren

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darcs 2.5 beta 1 release
by Reinier Lamers 12 Jul '10

12 Jul '10

Hi all, The darcs team would like to announce the immediate availability of darcs 2.5 beta 1. Important changes since darcs 2.4.4 are: * trackdown can now do binary search with the --bisect option * darcs always stores patch metadata encoded with UTF-8 * obliterate has a -o flag to save obliterated patch * amend-record now supports --ask-deps * apply now supports --match * amend-record has a new --keep-date option * inventory-changing commands (like record and pull) now operate in constant time with respect to the number of patches in the repository If you have installed the Haskell Platform or cabal-install, you can install this beta release by doing: $ cabal update $ cabal install darcs-beta Alternatively, you can download the tarball from http://darcs.net/releases/darcs-2.4.98.1.tar.gz and build it by hand as explained in the README file. Kind Regards, the darcs release manager, Reinier Lamers

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