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Generic information

You can apply for an account and a project using the community server.

Once you have an account and/or a project, you upload a Darcs repository as follows. First, initialize your repository on the server:

 $ ssh community.haskell.org
 you@haskell:~$ cd /srv/code/yourproject
 you@haskell:/srv/code/yourproject$ darcs init

Then, log out and push your repository:

 $ darcs push community.haskell.org:/srv/code/yourproject


If you have a project that you want to work on at the Hackathon, please describe it here.

Since Hackathons are great for teamwork, consider joining one of the projects mentioned below. If you're interested in one of these projects, add your name to the list of hackers under that project.

Haskell Platform 1.0

Finish the construction and roll out of the new Haskell Platform


  • dcoutts
  • dons
  • needed: windows/ macosx packagers.

Darcs Sprint #2


The second Darcs Sprint. Help improve our beloved DVCS! Add your nick to the list.


  • Reinier Lamers (tux_rocker)
  • Eric Kow (kowey)
  • Ben Moseley (benmos)
  • Ganesh Sittampalam (Heffalump)
  • Ian Lynagh (igloo)
  • Arjan Boeijink (arjanb)
  • Benedikt Schmidt (beschmi)
  • Petr Ročkai (mornfall)
  • Thorkil Naur (thorkilnaur)



Grapefruit is a library for Functional Reactive Programming (FRP) with a focus on user interfaces. FRP makes it possible to implement reactive and interactive systems in a declarative style. With Grapefruit, user interfaces are described as networks of communicating widgets and windows. Communication is done via different kinds of signals which describe temporal behavior.

Possible subprojects

  • graphics support
    • Jeff Heard expressed interest in adapting Hieroglyph to work with Grapefruit.
    • The classic version of Grapefruit contains quite a bit of OpenGL-based 3D animation stuff which could be ported to the current Grapefruit version.
    • We should also take a look at RSAGL.
  • improvements of the UI part and the GTK+-based UI backend
  • Qt-based UI backend
    • HQK should be used for this.
  • addition or integration of some kind of physics engine
    • There is, for example, Hpysics from Roman Cheplyaka (Feuerbach)


Grapefruit is BSD3-licensed, so all contributions to Grapefruit should be BSD3-licensed, too. If you don’t like this, please discuss this on the Grapefruit mailing list or contact Wolfgang Jeltsch.


  • Wolfgang Jeltsch (jeltsch)
  • Fraser Wilson
  • Roman Cheplyaka (Feuerbach)
  • Peter Verswyvelen
  • Thomas Davie



leksah is an attempt to develop a Haskell IDE in Haskell. Help adding cool features to this Wannabee IDE, like:

  • Generate export list
  • Code Formatter
  • Infer types
  • ...


  • Jürgen Nicklisch (jutaro)



Scion is a library that aims to provide IDE-like functionality on top of the GHC API. It aims to be front-end agnostic, thus serve as a common middle-layer for various Haskell programming frontends like Emacs, Vim, Yi, Eclipse, etc.

It currently only provides rudimentary functionality, such as loading a project and single-threaded background-typechecking. Currently, Scion's only frontend is Emacs, but a Vim frontend is in the underway. Possible Hackathon projects could be:

* Extend Scion's capabilities.  For example: cross-refs, jump to source, more type information
* Add another Scion frontend.  E.g., hook up Yi or Eclipse with scion 


* Thomas Schilling (nominolo)

Type class aliases


Type class aliases is a much wanted extension to Haskell proposed long ago by John Meacham (John's website, mailing list) that has never been implemented yet. It is time this extension sees the light of day!

GHC will be the target compiler. Perhaps GHC plugins (GHC wiki, The Monad Reader 12) are of help here?

Please have a look at the context alias wiki page and extend it if you can.


from Martijn van Steenbergen

As a starting point we'll focus on supporting the following syntax:

class alias FooBar a = (Foo a, Bar a)

x :: FooBar a => a
x = ...
from Wolfgang Jeltsch

A “class alias” actually doesn’t stand for a class but for a context (or a part of a context). So it might be better to choose a slightly different syntax:

context Foobar a = (Foo a, Bar a)

John Meacham proposes the following syntax for class aliases (context aliases) with superclass constraints:

class alias Num a = Eq a => (Additive a, Multiplicative a)

This is not consistent with the superclass syntax of class declarations. I think, we should use this syntax:

class alias Eq a => Num a = (Additive a, Multiplicative a)

Or better:

context Eq a => Num a = (Additive a, Multiplicative a)



Please list projects with which you are familiar. This way, people know whom to contact for more information or guidance on a particular project.

Name Projects
leather EMGM, multirec
jeltsch Grapefruit, HQK
jutaro leksah
sebas salvia, orchid, filestore
waern GHC (front-end), Haddock
Feuerbach xmonad, Hpysics
npouillard (ertai) yi, xmonad, darcs