A selection of pastries will be served as well as coffee, tea and juices.

GHC translates all of Haskell into a tiny intermediate language called Core, does a lot of optimisations on Core, and then generates executable code. In this talk I’ll take you on a journey into Core, with several goals. First, if you ever do performance-debugging of a Haskell program you may well find yourself staring at Core dumps to understand the program that the computer is executing (it may look nothing like the one you wrote!). Second, one way to extend GHC is to write a Core-to-Core plugin to do some cool optimisation or transformation that you want; and you can only do that if you understand Core.

Lastly, even if you want to do none of these things, I think you may enjoy the adventure. Core is a tiny but super-expressive language that can express all of Haskell, including all the types, and more beside. It pulls off this trick by drawing directly on System F, a mathematical calculus from type theory. Functional programming is amazing: serious theory leads directly to beautiful implementations.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

At Iris Connect we are developing a video sharing platform that is being deployed in over a thousand schools worldwide. As part of this process, the hundreds of gigabytes of videos uploaded from customers every day are a central part of our business. In this talk I will present our approach to video transcoding, and how we are using Haskell to meet our business needs. I will explain how our distributed architecture - inspired to FP desirable properties - allows us to reliably process hundreds of videos every day, dealing with high volume traffic and scaling at need, whilst keeping costs at bay.

Ludwig is a statically typed, declarative data description language. It's main use case is in Fugue, a product which lets you declare your cloud infrastructure in this language and then takes care of the rest. In this talk, we follow the interesting path from YAML to a statically typed data declaration DSL. On our way, we discuss some thoughts and patterns for implementing DSLs in Haskell.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

This is a story of an Infrastructure team at Zalora that implemented DevOps using Haskell and Nix.

The story covers: - picking a dynamically-typed functional language, suffering from it and recovering; - surviving in a cruel stringly-typed world of Unix; - implementing system software in Haskell and operating it; - overcoming challenges of Haskell deployment; - using Haskell to integrate with various 3rd-party services; - successfully abandoning traditional DevOps tooling that plagues the industry.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Haskell programming in the real world involves interacting with myriad legacy systems and libraries, many of which are written in C and require high-performance interop. inline-c is a package for writing mixed C/Haskell source code that seamlessly invokes native and foreign functions from these libraries in the same module. No FFI required.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

In this talk, I will describe the architecture and history of ghc-exactprint. ghc-exactprint is a library which enables programmers to easily specify refactoring operations by directly modifying the GHC AST. By leveraging the GHC parser and a suitable intermediate representation, we can refactor any haskell source file. I will also demonstrate two libraries which are already using ghc-exactprint to directly apply refactorings. HaRe has been rewritten to take advantage of this new machinery which has resulted in a significant reduction in complexity. Secondly, apply-refact automatically applies hlint suggestions. This program demonstrates one method in which the new foundation can be used in tandem with haskell-src-exts.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Idealised versions of board and simple arcade games render beautiful snippets of Haskell code. But real games need to deal with user input and output, animation, sound, asset management, UI plasticity, graphics acceleration, concurrency and networking, all of which involve the outside world and add side effects throughout the program. Most of the problems and patterns that we find in other kinds of software can also be found in some form in game programming. As such, game programming represents Haskell’s ultimate challenge.

There have been multiple attempts at proving that Haskell can be used to write games, but none have been definitive enough to convince those outside the community. Keera Studios was founded as a way to turn this situation around, by creating more and more complex games and demonstrate, by example, the possibilities and benefits of functional programming.

To prove that Haskell is a suitable choice for game programming, we want to do real multimedia and interact with real modern hardware, target (at least some) gaming platforms; and show that FP principles and techniques are beneficial for game development.

Our work in game programming has demonstrated that Haskell is a worthy contestant. We have created games that interact with Kinect, Wiimotes and Leapmotion, use OpenGL and SDL2 (SDL is used in games such as Angry Birds) for multimedia, target mobile platforms such as Android and are available for purchase on Google Play. We have also explored different ways to take advantage of pure functional programming, either by means of an embedded DSL (like in our Cross-platform Graphical Adventure Game Engine GALE) or using FRP (Keera Magic Cookies, Keera Breakout), and also for game testing and profiling purposes.

In this workshop I will demonstrate, by example, how to write games that combine these features, what to watch for, where the current challenges lie, and how we can, as a community, use the creative and fun process of game programming to bring Haskell to the world and vice versa.

Whoever wants to follow the talk with their own laptops should be able to compile this haskell package:

https://github.com/keera-studios/haskell-game-programming

There's no need to read/process the material ahead. If it compiles, they are good to go.

It usually takes just 2-7 minutes on my machine, so if they can't get it working before the talk, that's ok.

I strongly recommend using a sandbox.

In this talk, we'll take a deep dive into how to write high performance Haskell code, using what we've learned while optimizing the core Haskell libraries. We'll focus on understanding the memory layout of Haskell data types and how it can be optimized to make your program run faster. I'll give you several "rules of thumb" for writing code that performs well from the start, rather than having to be patched up once performance issues arise.

This talk complements Bryan O'Sullivan's 2014 talk on Performance Measurement and Optimization in Haskell, by focusing more on actual optimisations, rather than measuring performance.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Idealised versions of board and simple arcade games render beautiful snippets of Haskell code. But real games need to deal with user input and output, animation, sound, asset management, UI plasticity, graphics acceleration, concurrency and networking, all of which involve the outside world and add side effects throughout the program. Most of the problems and patterns that we find in other kinds of software can also be found in some form in game programming. As such, game programming represents Haskell’s ultimate challenge.

There have been multiple attempts at proving that Haskell can be used to write games, but none have been definitive enough to convince those outside the community. Keera Studios was founded as a way to turn this situation around, by creating more and more complex games and demonstrate, by example, the possibilities and benefits of functional programming.

To prove that Haskell is a suitable choice for game programming, we want to do real multimedia and interact with real modern hardware, target (at least some) gaming platforms; and show that FP principles and techniques are beneficial for game development.

Our work in game programming has demonstrated that Haskell is a worthy contestant. We have created games that interact with Kinect, Wiimotes and Leapmotion, use OpenGL and SDL2 (SDL is used in games such as Angry Birds) for multimedia, target mobile platforms such as Android and are available for purchase on Google Play. We have also explored different ways to take advantage of pure functional programming, either by means of an embedded DSL (like in our Cross-platform Graphical Adventure Game Engine GALE) or using FRP (Keera Magic Cookies, Keera Breakout), and also for game testing and profiling purposes.

In this workshop I will demonstrate, by example, how to write games that combine these features, what to watch for, where the current challenges lie, and how we can, as a community, use the creative and fun process of game programming to bring Haskell to the world and vice versa.

Whoever wants to follow the talk with their own laptops should be able to compile this haskell package:

https://github.com/keera-studios/haskell-game-programming

There's no need to read/process the material ahead. If it compiles, they are good to go.

It usually takes just 2-7 minutes on my machine, so if they can't get it working before the talk, that's ok.

I strongly recommend using a sandbox.

Infinipool produces software to make the process of transporting and storing data more efficient. We exploit the fact that a lot of real-world data is highly redundant. By finding these redundancies explicitly, we are able to avoid transporting and storing a large portion of the data. For our latest program, we chose to use Haskell as the implementation language. So far, the experience has been great. A particularly nice aspect was the abundance of fresh ideas and interesting libraries in the community. Libraries such as Haxl or servant are not only solving concrete problems that we had, but do so in a way that reading the actual papers and understanding the design and implementation is an intellectually rewarding experience. The mathematical feel of the language itself adds to that.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Oliver will be discussing the state of GUI programming in Haskell, briefly talking about the options available for application developers in 2015. He'll also touch on his experiences with building an interactive graphical application and where Haskell shines and where it needs to improve.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

This talk will describe HdpH: A domain specific language and runtime system for distributed parallel computation. We show, by example, the simplicity of the domain specific language and the features required to specify parallel computations. A description of the HdpH runtime system, work-stealing scheduler, and overall system architecture follows.

Time permitting we will discuss future directions for HdpH and show how it relates to other distributed frameworks such as Cloud Haskell, Eden and Gum/GpH.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Sometimes you cannot use Haskell to solve a problem because of external constraints. Despair not! You can still use it to develop your solution. I will talk about my experience designing solution and doing mini proof of concepts in Haskell in order to implement it with some other technology. This might seem like a waste of time at first but it yields very elegant solutions as it gives you another perspective on your problem

JsonGrammar is a combinator library for expressing bidrectional transformations between JSON expression trees (we use Aeson's Value datatype) and your own custom Haskell datatypes. Instead of writing separate fromJSON and toJSON functions, you write a single expression (a grammar) that expresses the conversions in both directions. You have full control over the mapping; for example, the property names in JSON and the Haskell record field names don't have to be the same, and the trees don't even have to be the same shape. This lightning talk will explain the building blocks of the API and how to combine them into full-fledged parsers/formatters.

Find out more about JsonGrammar here.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Tooling for Haskell development is a hot topic, since one of the biggest grievances in Haskell development is the issue of managing dependencies. Enter Docker, a tool that makes defining and running containers easy. Docker allows you to easily create reproducible environments across different architectures and operating systems, while being much more lightweight than full-fledged virtual machines. It brings testing and production environments a lot closer together, giving developers much more confidence to release new code.

Since Docker is a fairly new technology, there is still room for exploration to find the best way to set up development environments. In this talk I will give a short introduction to Docker and I will show how I set up my development environment using Docker containers. The main benefits of this setup will be portability across dev machines and isolating the development environment. To underline these benefits, I will demonstrate how I created and deployed a chat bot using Haskell.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

In this talk, Lennart will show how to design a strongly typed interface to an external library. The external library has some rather complex, dynamically checked, types. Making a strongly typed, easy-to-use version of the API uses several Haskell type system extensions, e.g., type level strings, closed type families, kind definitions. It even uses some extensions that are not quite in ghc yet.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

A selection of pastries will be served as well as coffee, tea and juices.

Haxl is a small framework for automatically batching and overlapping data-fetching. It was open-sourced by Facebook in 2014, and is in large-scale production use as part of Facebook's spam-filtering infrastructure. In this talk I'd like to explore some of the ways we can use Haxl to express not just data-fetching concurrency, but other kinds of concurrency too. I'll also take a look at the internals of Haxl, and explore whether we can generalize the simple model of round-based scheduling to allow more flexible scheduling strategies.

Shake, like Make, is a tool for writing build systems. However, unlike Make, Shake features monadic dependencies (your dependencies themselves can depend on the results of previous dependencies), polymorphic dependencies (your dependencies don't have to be files) and stable dependencies (if something rebuilds but doesn't change things that depend on it don't have to rebuild). These features make it much easier to define build systems that have accurate dependencies. Additionally, these features let you define your own custom build system, and then implement a Shake-based interpreter for it. It is often said that the easiest way to solve a problem is to define the perfect language for solving the problem, then write an interpreter. In this talk we'll see how to use Shake to apply that advice to build systems.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Servant (http://haskell-servant.github.io/) is a recent library for writing web applications with a quite novel approach: users describe web APIs with a type-level DSL. The library then uses that description, which can be inspected and transformed for great good to: - provide very strong type safety guarantees on your request handlers, - derive Haskell or Javascript functions to query the aforementionned API, - automatically generate the API documentation, - overall make the code as boilerplate-free as possible, by having all the important information about your API in the same place. This very hands-on talk hopes to demonstrate what the every day web application developer can get out of servant as-is but also how one can extend the (unopinionated) library in every possible direction to get an opinionated, tailor-made web framework.

Are the logical foundations of your favourite programming language not entirely satisfactory? Is your everyday programming work far too useful and practical? Have I got the talk for you! We’ll learn how parametric higher-order abstract syntax (PHOAS) makes it simple and easy to embed a logic in your favourite programming language — as long as it’s Haskell, Agda, or Idris. Then, by Jove, we’re going to prove some theorems!

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

The opinions about Scala in the Haskell community differ widely. Most will immediately point out reasons why they think Scala is complex and that Haskell is so much better. But is it really? In this talk, we will take a radically different approach: We will outline what Haskell can learn from Scala and depart from the usual narrative that it is just a “lesser Haskell for the JVM”. Topics will include dependent types and computations at the type level, composability and modularity, and compile-time reflection and generic programming. We will also compare and contrast the appearance of several popular “design patterns” in Haskell and Scala. If you’re interested in hearing about “Hasochism”, “shapeless”, and how to make the Scala compiler cry, you should definitely attend this session.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

Often, categorists will speak about "universal properties" when discussing basic constructions. Understanding what these are can be one of the more confusing aspects of coming to terms with category theory. But it turns out that there is one weird trick that lets us take universal properties and translate them directly into executable code. In doing so, we can better understand just what it means for something to be a universal property, and for that matter, how to think of the relationship between functions and data. The insights from this sort of approach are broadly applicable to real-world practice when we think about how to structure our data to capture just what it should, and nothing else. This talk will start from the very basics, and hopefully leave the audience with a taste of practical categorical intuition, summarized in the slogan "Asking what and asking how are asking the same thing."

The "Hands-on introduction to Opaleye" workshop will be led by Tom Ellis, Opaleye's principal developer. The workshop will last a couple of hours and will teach developers to write Opaleye code on their own machines as they follow the lesson. A shared instance of Postgres will be provided for everyone to use and the aim is to complete a small analytical web app by the end of the session. Templates for anything non-Opaleye-related will be provided so participants can spend all their time learning about Opaleye.

Participants should have a working installation of GHC and Cabal.

Effect handlers have recently been proposed as a new means of working with compositional effects, and threaten to replace monad transformers. Their key advantage is a cleaner way of expressing semantics since they are defined in terms of algebras. An often misunderstood aspect is how they compare to monad transformers with respect to compositionality of effects. This talk will introduce both methodologies and show how they relate.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!

The "Hands-on introduction to Opaleye" workshop will be led by Tom Ellis, Opaleye's principal developer. The workshop will last a couple of hours and will teach developers to write Opaleye code on their own machines as they follow the lesson. A shared instance of Postgres will be provided for everyone to use and the aim is to complete a small analytical web app by the end of the session. Templates for anything non-Opaleye-related will be provided so participants can spend all their time learning about Opaleye.

Participants should have a working installation of GHC and Cabal.

GHCJS is a Haskell to JavaScript compiler based on GHC. Among the improvements in the past year are official Cabal integration, support for CPU profiling and an overhaul of the ghcjs-base library. A recent addition is an experimental REPL, making it easier than ever to interact with Haskell in a browser or node.js environment. I will discuss the current state of the project, and explain what impact recent developments like ECMAScript 6 will have on how various Haskell concepts are translated to JavaScript. I'll demonstrate the GHCJS development tools and libraries with some examples of interacting with the JavaScript environment, with a focus on concurrency and event handling.

A panel discussion featuring several speakers of the #HaskellX 2015.

Join us at the Haskell eXchange in 2016!

Want to learn about the latest innovations in Haskell? Join 200+ Haskell and functional programmers to learn and share skills with some of the world's top Haskell experts at the Haskell eXchange 2016 in London. Find out all about Haskell's infrastructure roadmap, learn how Haskell is used in academia and enterprise and discover how Haskell is changing the way our industry tackles complex engineering problems. Early bird tickets already available!