July 2010 - Haskell-Cafe

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 12 Jul '10

12 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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Float instance of Data.Bits
by Sam Martin 12 Jul '10

12 Jul '10

Hi, Is there a particular reason Float, Double, etc do not have instances of Data.Bits in the standard libraries? I note the Haskell 2010 report doesn't include them either. In fact, I'm not actually sure how you'd implement the instance for floating point types without having some kind of compiler-specific extension, or a c-binding. Could anyone fill in my missing knowledge here? Cheers, Sam

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ANNOUNCE: fgl-5.4.2.3
by Ivan Lazar Miljenovic 12 Jul '10

12 Jul '10

I'm pleased to present the first new release of fgl [1] since Thomas Bereknyei took over maintaining it from Martin Erwig. [1] http://hackage.haskell.org/package/fgl Before people start panicking, rioting, etc., please check the version number: this is just a bug-fix release, and not the complete re-write version which we've been talking about (since we got a little sidetracked, etc.). As such, the API hasn't changed, and this should fit right in to packages already using fgl (sorry to all those people who followed my advice and put "fgl == 5.4.2.2" in the build-depends fields of their packages' .cabal files, but I didn't expect to make another 5.4.y release). The exact change that has been made is to fix a bug pointed out to me by Tristan Allwood, in that Data.Graph.Inductive.PatriciaTree didn't support multiple edges (and furthermore this wasn't specified in the documentation). This has now been rectified. As an indication of what these changes mean, see this sample call graph produced by my SourceGraph program; when using PatriciaTree from fgl-5.4.2.2 the lines were all the same thickness; now there is among other things a loop of width 32 on getExp and a line of width 7 from getExp to maybeEnt. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Equivalence of two expressions
by Grigory Sarnitskiy 12 Jul '10

12 Jul '10

I'm not very familiar with algebra and I have a question. Imagine we have ring K. We also have two expressions formed by elements from K and binary operations (+) (*) from K. Can we decide weather these two expressions are equivalent? If there is such an algorithm, where can I find something in Haskell about it? If there is no such algorithm for a ring, maybe there is for a field?

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haskell on suse?
by gladstein＠gladstein.com 12 Jul '10

12 Jul '10

I've been spoiled by package managers that download and install everything for you, and I've forgotten how RPM works. In particular, I want to install Haskell on suse, and I read that "RPMs are available from openSUSE. " I followed the link, and found a bunch of folders of folders of RPM files. What exactly should I do to install Haskell? Sorry about the newbicity of this request, but I'm totally stumped. If suse isn't a well-supported platform, I'll switch. Thanks in advance.

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ANNOUCE: graphviz-2999.10.0.0
by Ivan Lazar Miljenovic 12 Jul '10

12 Jul '10

I'm pleased to announce a new version of my graphviz [1] library that provides bindings to the Graphviz [2] suite of tools for visualising graphs. [1]: http://hackage.haskell.org/package/graphviz [2]: http://graphviz.org/ Changes in this release: * I followed my own advice and put in bounds on the version of FGL it used... * Conversion of FGL-style graphs to `DotRepr` values is now achieved using the new `GraphvizParams` configuration type. This allows us to define a single parameter that stores all the conversion functions to pass around rather than having to pass around several functions. This also allows all the non-clustered and clustered functions to be collapsed together, whereas what used to be handled by the primed functions is now achieved by using the `setDirectedness` function. There are three default `GraphvizParams` available: - `defaultParams` provides some sensible defaults (no attributes or clustering). - `nonClusteredParams` is an alias of `defaultParams` where the clustering type is explicitly set to be `()` for cases where you don't want any clustering at all (whereas `defaultParams` allows you to set your own clustering functions). - `blankParams` sets all fields to be `undefined`; this is useful for situations where you have functions that will set some values for you and there is no sensible default you can use (mainly for the clustering function). * Expansion of the `DotRepr` class: - More common functions are now defined as methods (`getID`, etc.). - The ability to get more information about the structure of the `DotRepr` graph, as well as where all the `DotNode`s are, etc. - `graphNodes` now returns `DotNode`s defined only as part of `DotEdge`s, and will also merge duplicate `DotNode`s together. - `graphNodes` and `graphEdges` also return `GlobalAttributes` that apply to them. * The `Point` type now only has one constructor: `Point Double Double`. The `Int`-only constructor was present due to historical purposes and I thought that the `Pos` value for a `DotNode` would always be a pair of `Int`s; this turns out not to be the case (and accounted for some bugs in older versions of my SourceGraph tool; it's taken me this long to remember to fix this...). * `SortV` and `PrismOverlap` now only take `Word16` values rather than `Int`s, as they're not meant to allow negative values (the choice of using `Word16` rather than `Word` was arbitrary, and because it's unlikely those values will be large enough to require the larger values available in `Word`). * `NodeCluster` has been generalised to not have to take an `LNode` for the node type; the type alias `LNodeCluster` is available if you still want this. * Several documentation typos fixed, including one spotted by Kevin Quick. * The test-suite now allows running individual tests. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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ANNOUNCE: SourceGraph-0.6.1.1 and Graphalyze-0.10.0.0
by Ivan Lazar Miljenovic 12 Jul '10

12 Jul '10

I'm pleased to announce updated versions of SourceGraph [1] (my graph-theoretic static analysis tool for Haskell) and Graphalyze [2] (a library for graph-theoretic analysis of relationships in discrete data). [1]: http://hackage.haskell.org/package/SourceGraph [2]: http://hackage.haskell.org/package/Graphalyze This version of SourceGraph now (should) only consider executables listed in .cabal files as being buildable, and both packages have been updated to use the latest versions of fgl (as well as following my own advice in putting an upper bound on the version of fgl being used...), graphviz and haskell-src-exts (SourceGraph only). Please note that SourceGraph-0.6.1.0 was a version I forgot to upload (and just realised this when I wondered why it wasn't appearing on Hackage...). The big change that should be apparent with this version of SourceGraph is that thanks to the changes I just made to the newly-uploaded fgl-5.4.2.3, multiple edges are finally being handled/visualised properly; for example see the nice thick lines in http://code.haskell.org/~ivanm/Sample_SourceGraph/SourceGraph/graphs/codeCo… (which represents among other things 32 recursive calls within getExp and 7 calls from getExp to maybeEnt). I forgot to put this in the TODOs, but here are my future plans for these packages. They're rather ambitious and I have no idea when I'll get around to them, but for all intents the only work I'm going to do on them until I do these splitting up goals is bug-fixes, etc. Graphalyze ---------- Graphalyze is going to fade away: I'm going to integrate its data -> graph conversion utilities into either my new graph library I'm going to work on during AusHack or into the successor for fgl Thomas Bereknyei and are working on (whatever we'll end up calling it), the Data.Graph.Analysis.Algorithms modules into graph-algorithms and fgl-algorithms packages and the reporting stuff into its own reporting library with different backends (pandoc, blaze, etc.). SourceGraph ----------- I want to split out and formalise the whole call-graph definitions and concepts into its own library and have sub-libraries for different languages to be able to have their own code -> call-graph conversions (so it can also be used for language-c, language-python, etc.). SourceGraph itself would then be more flexible in terms of what languages it can deal with (so it might even be possible to integrate C source files in a Haskell package into the call graph!). -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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