Zürich Friends of Haskell

The Zürich Friends of Haskell is a club founded to foster the worldwide knowledge of functional programming, and Haskell in particular. We organise meetups and events in the Zürich area.

About us

The HaskellerZ meetup group has been around since 2011. After organising many meetups and events, in particular ZuriHac, which attracts people from all over the world, there was a need to formalise our group a bit more.

In the short term, this allows us to work together better with sponsors for ZuriHac. In the long term, however, we would like to guarantee the long-time success of a Zurich-based Haskell interest group, not dependent on one or two key volunteers.

The rules are set up so that we encourage non-monetary contributions (e.g. giving a talk). Of course, membership is optional and not required to attend any of our events.

Become a member!

For members, we ask a yearly contribution of either:

  1. giving at least one talk at the Zurich HaskellerZ meetup,
  2. helping organize ZuriHac in an official role,
  3. serving on the board of directors for the Zurich Friends of Haskell
  4. providing other voluntary work asked for by the board of directors, or
  5. paying a membership fee of 50 CHF (students 25 CHF).

Sign up for Membership

Last meetup

Simon Meier - Test-Driven Development of a Unification Algorithm

Thursday 20 September, 19:00

"If it type checks, then it works." is a phrase that is true more often for Haskell code than for code written in other languages. Tests are though still needed! In particular for code which depends on conditions not captured by the type system. An example of such code is (first-order) unification [1], a classic algorithm used for example in type checkers, Prolog interpreters, and theorem provers.

In this interactive live-coding talk, we'll together
- revisit the theory of first-order terms, substitutions, and unification;
- explore how to use hedgehog [2] to implement unification in a test-driven fashion; and
- learn how to use ghcid [3] to get live test feedback.

PS: In case you wonder: why unification? Blinded by the ease of writing (mostly) correct Haskell code, past-me was not very big into testing. During my PhD, I've learned the hard way that unification is one of the algorithms that has ample room for subtle mistakes -- and tests are absolutely a must! Back then, I've written a number of regression tests to capture the problems after the fact. This talk is the result of present-me exploring how TDD combined with modern property-based testing fares in detecting these subtle mistakes up-front.

[1] https://en.wikipedia.org/wiki/Unification_(computer_science)#First-order_term
[2] http://hackage.haskell.org/package/hedgehog
[3] http://hackage.haskell.org/package/ghcid

Past meetups


Our main yearly event is the organisation of ZuriHac, a yearly Haskell Hackathon that attracts over 300 attendees. It is probably one of the oldest and definitely the largest Haskell Hackathon currently in existence.

The first ZuriHac was organised in 2010 at the Zürich Google office by Johan Tibell and Christophe Poucet. Currently, we are organising it at the Hochschule für Technik Rapperswil with the help of many Zürich Friends of Haskell members and volunteers.


We try to record all of our meetups and keynotes so Friends of Haskell who are not in the Zürich area can enjoy the content as well.

This playlist contains all our Haskell-related videos.

We have also collected the slides of the presentations in this repository. Unfortunately, the collection is currently incomplete.


The board of the Zürich Friends of Haskell association currently consists of: