DHD UHac/DHD Program

This is the final program for the Dutch HUG Day.

Time	Title	Speaker
9:30	Coffee and Tea
10:00	Welcome	Sean Leather, Stef Joosten
10:15	Supporting Different Versions of the WebSockets Protocol	Jasper Van der Jeugt
10:45	Building Your Own Haskell Ecosystem	Erik Hesselink
11:15	Model Checking Abstract Syntax Trees	Pascal Hof
11:45	Lightning Talks
	DotFS - or How Fred Solved His Config Clutter	Paul van der Walt, Sjoerd Timmer
	Snap and Gruze	Kevin Jardine
	Invitation to Participate in a Functional Programming Case Study	Jurriaan Hage
12:15	Lunch (provided by Ordina)
13:15	Haskell in Practice: How Haskell Has Been Used in a (Paid) IT Project	Stef Joosten, Martijn Schrage
13:45	fclabels: First Class Record Labels for Haskell	Sebastiaan Visser
14:15	GHC 7.6, More Well-Typed Than Ever	José Pedro Magalhães
14:45	Lightning Talks
	Holes in GHC	Thijs Alkemade
	Applicative Regular Expressions	Roman Cheplyaka
	How I Generate My Homepage	Wouter Swierstra
15:15	Closing	Jurriën Stutterheim
15:30	Depart for UHac

Summaries

Supporting Different Versions of the WebSockets Protocol

Jasper Van der Jeugt (Ghent)

The Haskell websockets library allows you to write WebSocket-enabled servers in Haskell, bidirectional communication with the browser. However, browsers and their related specifications change fast, and there are different versions of the WebSockets protocol. This talk discusses a type-safe technique which disallows the programmer from using primitives not available in the chosen version, while still allowing the latest features.

Building Your Own Haskell ecosystem

Erik Hesselink (Silk)

When you develop a lot of different Haskell packages that work together, managing all these packages and their versions can be difficult. In this talk, I'll explain how we deal with this at Silk. I will show how to use Hackage 2.0 to build your own internal package repository, how to use cabal-dev to manage installed packages, and show a tool for bumping package versions. Together, this makes working on large amounts of packages with multiple people much easier.

• bumper on Hackage
• bumper on GitHub

Model Checking Abstract Syntax Trees

Pascal Hof (TU Dortmund)

Model checking turned out to be a useful tool for the analysis of programs. Usually one transforms abstract syntax trees to control flow graphs, which offer a abstract representation of program behavior. Whenever one is not focused on program behavior but on structural properties of the program (e.g. semantic analysis of a compiler), model checking the abstract syntax tree comes in handy. My talk introduces a problem, which can be solved using model checking abstract syntax trees. Additionally, different approaches for a implementation will be discussed.

DotFS - or How Fred Solved His Config Clutter

Paul van der Walt (UU), Sjoerd Timmer (UU)

Everyone who has more than one account on Linux/Unix/OS X systems knows how hard is can be to keep track of all the different config files in your home directory. .vimrc, .muttrc, .hgrc, .screenrc, .bashrc, and .xinitrc are just a few, but we're sure you can come up with many more yourself. Imagine how wonderful your life could be if you just had an easy tool to keep track of different versions of all these files on all your machines. We argue that traditional version control systems on their own are not up the task and we provide an alternative.

• dotfs on Hackage
• dotfs on GitHub

Snap and Gruze

Kevin Jardine

Developing an astronomy application using Snap and an experimental entity-attribute-value store for Haskell.

• Gruze-Store on GitHub

Invitation to Participate in a Functional Programming Case Study

Jurriaan Hage (UU)

I want to invite you to participate in an experiment in Haskell. In this experiment we are going to pit HaRe (the Haskell Refactorer) against Holmes (my plagiarism detector). The goal is to find out how much time somebody needs to refactor a Haskell program into something that is not recognizable by Holmes as plagiarism. We shall be looking at two groups of study: experienced programmers (we shall pretend they are paid for by newbies to make their assignments for them, and to do so without starting from scratch), and the newbies themselves. This experiment is a collaboration with Simon Thompson of Kent. He will take charge of the newbies, my task is to perform the experiment with experienced Haskell programmers, which is why I am now seeking for participants.

Haskell in Practice: How Haskell Has Been Used in a (Paid) IT Project

Stef Joosten (Ordina), Martijn Schrage (Oblomov Systems)

This presentation shows how new thinking helps the judiciary to gain control over and to reduce cost in a landscape of many different IT systems that serve the courts of law in the Netherlands.

Although Haskell plays a role outside the limelight, the results have become possible because of a tool, Ampersand, which has been built in Haskell.

The presentation is accompanied by a brief demonstration.

fclabels: First Class Record Labels for Haskell

Sebastiaan Visser (Silk)

Haskell's record system for algebraic datatypes uses labels as accessors for fields within constructors. Record labels can be used for both selection and modification of individual fields within value, but only selection can be composed in a natural way. The special syntax for updates makes composing modifications very cumbersome. The fclabels package tries to solve this problem by implementing field accessors as first class Haskell values instead of special syntax. Labels are implemented as lenses and can easily be composed for both selection and modification. To avoid boilerplate labels can be derived using Template Haskell. This talk will give a brief introduction into the usage of the library and will show a bit of the inner workings as a bridge to future extensions.

• fclabels on Hackage
• fclabels on GitHub

GHC 7.6, More Well-Typed Than Ever

José Pedro Magalhães (UU)

With each new version, GHC brings new and exciting type-level features to the Haskell language. In this talk we look at some upcoming features for GHC 7.6: data kinds, kind polymorphism, type-level literals, and deferred type errors. We show through some example programs how to take advantage of the new features, and what possibilities they open for Haskell programmers.

• Slides

Holes in GHC

Thijs Alkemade (UU)

This will be a demonstration of work-in-progress on adding holes for type-based debugging with GHC. See the GHC Trac page for details.

Applicative Regular Expressions

Roman Cheplyaka

In this short talk I am going to describe the regex-applicative project:

• what it is about
• how it compares to other parsing combinator libraries
• its current state and unsolved problems

I'll be glad to accept any help during UHac.