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(LGtk: GUI framework in Haskell)

Revision as of 20:07, 4 June 2014

These are some of the projects that ZuriHac 2014 attendees will be working on:


1 Aeson


  • Bas van Dijk (Faster JSON encoder)

2 Scion / Lambdachine

  • Thomas Schilling

3 Hakyll


  • Jasper van der Jeugt
  • David Wagner

4 Haskell: the Gathering

Implementation of Magic: the Gathering in Haskell. We will work on the rules engine, card implementations (both in Haskell) and the web client (TypeScript/HTML). Help is welcome in all three areas.

  • Martijn van Steenbergen

5 T-Digest

Persistent implementation of the T-Digest ( quantile estimation data structure, for use in ekg.

  • Johan Tibell

6 Nomyx

Nomyx is a game where you can change the rules while playing:

  • Corentin Dupont (I'll work on new features and bugs . Help/advices are welcome :))

7 Snap


  • Alfredo Di Napoli - I have in mind a couple of interesting features I would like to see in snap.

8 Hackage


  • Ian Ross (tags interface)
  • Alp Mestanogullari (most likely a nice statistics page)

9 GHC bug squashing

I plan to fix a few random GHC bugs and I’m more than happy to guide GHC-newbies in doing the same. Planning and coordination will happen at I started to collect some suitable tickets, feel free to add some.

  • Joachim Breitner
  • Lorenzo Tabacchini

10 Oauth-provider


  • Gerolf Seitz (I would like to have a RFC / code-review on oauth-provider)

11 Math Symbols in Diagrams

I'd like to be able to label diagrams with mats symbols and fonts: There has been some discussion of this on #diagrams and I need to write up an approach. NB I have used diagrams a lot but never hacked on the package itself.

  • Dominic Steinitz
  • David Wagner

12 Propellor


  • David Wagner (I would like to add monit support to propellor).

13 Rest

We have recently open sourced our rest framework which Erik Hesselink gave a presentation about at last years ZuriHac. It provides a declarative way to define REST resources (rest-core) which can be used to run the api on different web servers (rest-happstack, rest-snap) and to automatically generate clients for different languages along with documentation and usage examples (rest-gen). We want to write introductory materials to get people started. We'd appreciate help and we'd be happy to sit down with anyone wanting to get started with rest.

  • Adam Bergmark
  • Erik Hesselink
  • Sebastiaan Visser

Project ideas:

  • Write tutorials based on the rest-example blog application
  • Refactor the rest-gen haskell client generation to use haskell-src-exts
  • Write a test-framework that runs an api and uses its generated client

14 Erlang Interpreter in Haskell

This is my learning project for Haskell, and since I come from Erlang background I have chosen to combine both things into one.

  • Gleb Peregud
  • Felipe Zapata

15 LGtk: GUI framework in Haskell

See and I would like to work on a browser backend with GHCJS and improving documentation (writing a tutorial especially).

  • Péter Diviánszky
  • Pék Dániel

16 LambdaCube 3D - Stunts game

LambdaCube 3D is a domain specific language and library that makes it possible to program GPUs in a purely functional style. During ZuriHac I'll implement FRP based menu for Stunts demo. If you are interested in game development join! :)

  • Csaba Hruska

17 extensible-effects

Revise the package's API and prepare the 2.0 version.

WIP is at

  • Roman Cheplyaka

18 complexity

Complexity is a tool to measure the emprical complexity of functions. During Zurihac we want to rewrite complexity so that it makes use of the excellent Criterion package. We also want to rewrite the reporting part. Perhaps not depend on any GUI toolkits but instead generate a static HTML report.

  • Roel van Dijk
  • Tim Schwarte

19 Binding for librabbitmq


  • Mikael Brockman

20 The `psqueues` package

Help creating a
package providing performant implementations of priority search queues. These are data structures that manage a set of triples of the form
(key, priority, value)
and allow efficient lookup by key and efficient lookup and removal of the element with minimal priority. More precisely, I imagine that the package should provide
, and
data structures whose requirements and API are analogous to
s, and general

The implementation plan is as follows.

  • The APIs are structured analogously to the existing
    APIs extended with additional functions inspired by the
  • The implementation of
    is based on Hinze's construction and the code already provided in the
  • The implementation of
    s uses a radix-tree that stores
    (key, priority, value)
    triples in inner nodes and enforces the min-heap property. There is a draft of this structure in TODO URL, which significantly outperforms the
    package specialized to
    s (see [1]).
  • The implementation of the
    s uses an
    over the hash values of the keys and manages the collisions using a
    to guarantee logarithmic worst-case performance for
    s and

The two main use cases of the structures provided by this package are the GHC IO manager and pure LRU caches, which are used in many web application backends to speedup data storage access. However, I'm sure there are more use cases for efficient priority search queues.

There is a branch in my fork of containers that contains a minimal, but working and well-performing IntPSQ. The work that remains to be done is to

  • incorporate and modernize the
    from the
  • combine
    s and
    s to form a
  • implement extensive tests
  • implement more realistic benchmarks for the above two usecases

This project is well-suited for a group of Haskellers starting at intermediate level, as the work can be parallelized well and the individual tasks are small and well-defined.

Project lead: Simon Meier


  • Alex Sayers
  • Jasper Van der Jeugt

21 The `th-versions` package

The goal of this package would be to implement Template Haskell functions to look around in the environment for build time information: timestamp, git commit hash (and info on dirtiness maybe), content of VERSION file while walking upwards from the current directory, path of compilation, hostname of compilation, architecture, etc.

Then we would embed this to the program/library being compiled with a splice.

Template Haskell may not be everyone's favorite extension, but it's definitely better than CPP. :)

This project is well-suited for some advanced beginners who want to learn about TemplateHaskell and already create some useful new hackage package in the process.

If you have questions, feel free to ask:

  • Gergely Risko
  • Mihaly Barasz

22 GHC `--make-link-only` flag

At nilcons we use makefiles to drive Haskell compilation for various reasons. The final linking has to be done with `ghc --make`, because that's the easiest way to call the linker with all the necessary packages correctly passed.

But we want to assert that this `ghc --make` shouldn't do any compilations at all, because previous parts of the makefile should have taken care of that. If GHC detects that compilations are needed and linking is not enough, that's a serious mistake somewhere in our system.

Currently this check is implemented by grepping for "Compiling" in the output of `ghc --make`, which is a bit kludgy.

Therefore we would like to implement the `--make-link-only` mode (open to better names) that will do the same thing as `--make` linking wise, but if compilations are needed it will issue a fatal error.

  • Gergely Risko
  • Mihaly Barasz

23 GHC: selectively ignore some warnings

`-fwarn-name-shadowing` is a very useful warning that can uncover a lot of hard to catch bugs. But it's annoying when a short name is used locally in a small let that is otherwise defined in the Prelude or in lens: e.g. `map`, `to`, `view`.

Therefore we would like to add annotations that can be used to ignore name shadowing for the binding, something like this:

f = ...
    let {-# SHADOWS #-} map = defaultMapWhatever
    in gameWithAnotherMap map

We're not sure about the syntax here, so we're happy to hear your opinions!

A similar request for `-fwarn-unused-binds` is already in trac under #3283, we'll try to handle that too.

  • Gergely Risko
  • Mihaly Barasz