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ANN: libxkbcommon bindings
by Auke Booij 13 Aug '13

13 Aug '13

There's a lot of work nowadays towards replacing the X11 infrastructure. Notably, wayland intends to replace some of the functionality that X.Org now provides, and it uses libxkbcommon to replace the X11 XKB.h keyboard event parsing code (actually it is not a dependency, but it is the de facto standard). I think it would be great if haskell supports these new libraries as soon as they are being used, which is why I wrote haskell FFI bindings for libxkbcommon. Partly because I am not exactly an experienced haskell developer, and partly because I am unsure how users will use libxkbcommon, at this point haskell-xkbcommon is rather thin. I intend to add a layer of code that makes this look more haskelly based on your feedback. Hence, feedback is MOST welcome in any area, be it code style, documentation, or API preferences. I did not upload haskell-xkbcommon to hackage yet - should I at this stage? https://github.com/tulcod/haskell-xkbcommon PS: If this turns out to be a success, I'd like to develop wayland bindings as well, so if you have anything to say about that feel free to contact me.

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Default query for AcidState?
by Kyle Hanson 12 Aug '13

12 Aug '13

I am looking for something with a type signature like this: grabAcidState :: AcidState as -> IO as basically I just want to return my data from database abstractly or based on a class. The reason for this is because I want to have a class instance of state and then I can implement my library like so: data MyCoolData :: MyCoolData T.Text class HasCoolData a where getCoolDataList :: a -> MyCoolData grabStoredList :: HasCoolData as => AcidState as -> IO [MyCoolData] grabStoredList as = do cs <- grabAcidState as return $ getCoolDataList cs and users could implement it like so: data AppState = AppState { someCoolData :: [MyCoolData] } instance HasCoolData AppState { getCoolDataList = someCoolData } However trying to implement this simple behavior has been proving quite difficult. Maybe I am making this too difficult and I should just have a seperate AcidState datatype for my library. Any help would be appreciated.

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ANN: restricted-workers-0.1
by Daniel F 12 Aug '13

12 Aug '13

Introducing: restricted-workers library, version 0.1.0. This library provides an abstract interface for running various kinds of workers under resource restrictions. It is being developed as part of the interactive-diagrams project and you can read more about the origins of the library in my GSoC report: <http://parenz.wordpress.com/2013/07/15/interactive-diagrams-gsoc-progress-r…> The library provides a convenient way of running worker processes, saving data obtained by the workers at start-up, a simple pool abstraction and a configurable security and resource limitations. Right now there are several kinds of security restrictions that could be applied to the worker process: - RLimits - chroot jail - custom process euid - cgroups - process niceness - SELinux security context You can read more about the library on the wiki: <https://github.com/co-dan/interactive-diagrams/wiki/Restricted-Workers> The library has been uploaded to hackage and you can install it using cabal-install. -- Thanks -- Daniil Frumin

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Value-weak hash tables in Haskell ?
by Aleksey Uymanov 11 Aug '13

11 Aug '13

Hello, haskellers. Is there any package implementing magic hash tables weak in value? I mean when the value is garbage collected, then this key+value authomatically removes from the hash table. -- Aleksey Uymanov <s9gf4ult(a)gmail.com>

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Rank N Kinds
by Wvv 10 Aug '13

10 Aug '13

It was discussed a bit here: http://ghc.haskell.org/trac/ghc/ticket/8090 Rank N Kinds: Main Idea is: If we assume an infinite hierarchy of classifications, we have True :: Bool :: * :: ** :: *** :: **** :: ... Bool = False, True, ... * = Bool, Sting, Maybe Int, ... ** = *, *->Bool, *->(*->*), ... *** = **, **->*, (**->**)->*, ... ... RankNKinds is also a part of lambda-cube. PlyKinds is just type of ** (Rank2Kinds) class Foo (a :: k) where <<==>> class Foo (a :: **) where *** is significant to work with ** data and classes; more general: Rank(N)Kinds is significant to work with Rank(N-1)Kinds First useful use is in Typeable. In GHC 7.8 class Typeable (a::k) where ... <<==>> class Typeable (a ::**) where ... But we can't write data Foo (a::k)->(a::k)->* ... deriving Typeable If we redeclare class Typeable (a ::***) where ... or even class Typeable (a ::******) where ... it becomes far enough for many years I'm asking to find other useful examples -- View this message in context: http://haskell.1045720.n5.nabble.com/Rank-N-Kinds-tp5733482.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Installling Leksah on ghc7.6.3 with haskell-platform 2013?
by Carlo Hamalainen 10 Aug '13

10 Aug '13

Hi, I'm trying to install Leksah from hackage on my Debian testing laptop, which has ghc 7.6.3 and the Haskell Platform 2013. I fixed a bunch of errors about "catch" not being exported from the Prelude, but now I'm stuck on these two errors in leksah-server-0.8.0.5: [10 of 13] Compiling IDE.Utils.GHCUtils ( src/IDE/Utils/GHCUtils.hs, dist/build/IDE/Utils/GHCUtils.o ) src/IDE/Utils/GHCUtils.hs:94:40-62: Not in scope: data constructor `Opt_ReadUserPackageConf' src/IDE/Utils/GHCUtils.hs:161:44-50: Not in scope: data constructor `Opt_Cpp' Perhaps you meant one of these: `Opt_CSE' (imported from GHC), `Opt_Pp' (imported from GHC) Where have Opt_ReadUserPackageConf and Opt_Cpp gone in ghc 7.6.3? Cheers, -- Carlo

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Importing more modules by default
by aditya bhargava 10 Aug '13

10 Aug '13

Hi there, It seems like every Haskell program I write imports the following modules: Control.Monad Control.Applicative Data.Maybe Data.List Is there a good reason why these modules aren't imported by default? When I write a simple script usually a 1/4th of the script is just imports, and my code just looks uglier. Adit

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Re: [Haskell-cafe] Some philosophy (Was: Alternative name for return)
by man 09 Aug '13

09 Aug '13

On Fri, Aug 9, 2013 at 5:44 PM, Jerzy Karczmarczuk < jerzy.karczmarczuk(a)unicaen.fr> wrote: > I have the impression that a nice part of our dispute comes from the fact > that despite our ambitions, and a decent /technical/ level of understanding > of what we are talking about, most of us are (and I am one of the worst...) > -- > > -- pitiful philosophers... > I just leave this here, Analytic Philosophy: An Anthology http://www.amazon.com/gp/product/0631216472 -- happy hacking... man

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translate imperative pseudo code into haskell
by Joerg Fritsch 09 Aug '13

09 Aug '13

I would need some help to get to a reasonable function involving the DB read, addition and multiplication. for 0 <= i < row dimension of A for 0 <= j < column dimension of B for 0 <= k < column dimension of A = row dimension of B sum += (read A (i,k))* (read B(k,j)) I started like this but then somehow lost the compass: main = do map my.read (map (\(x,y) -> "matrixA:" ++ show row ++ ":" ++ show column) [ (i, j, k) | i <- [1..50], j <- [1..20], k <- [1..30] ]) Can you pls help? --Joerg

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ANN: hi-0.0.2, a Haskell project generator
by Daisuke Fujimura 09 Aug '13

09 Aug '13

Hello cafe, I'm very happy to announce the release of hi, a Haskell project generator. http://hackage.haskell.org/package/hi This application will generate a scaffold for new Haskell project with given command line argument(or value in configuration file), using git repository as a template. If you frequently create new project which has test suite in hspec, generating new project by hi will be a good alternative to cabal-init. It comes with test suite in hspec and already buildable. A project made by the default configuration is here. https://github.com/fujimura/hi-example More details is in the README: https://github.com/fujimura/hi Hope you enjoy it :-) -- Fujimura Daisuke http://fujimuradaisuke.com/

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