Category theory can be thought of as being "very abstract algebra". It is thought of as "too abstract" by some people, and as "abstract nonsense" by some others. In this talk I will show that while it is abstract, it is far from being nonsense. I will argue that the abstraction has a purpose and that broad applicability is one of the powerful consequences. To demonstrate this, I will show how I apply concepts of category theory to important questions of life such as prejudice, privilege, blame and responsibility. I will introduce the category theory concepts from scratch so no prior knowledge is needed. These concepts will include objects and morphisms, isomorphisms and universal properties.

Back in the 80's, one approach to compiling functional programming languages was to compile down to combinators such as SKI. John Hughes' initial work on supercombinators changed the way folks thought about compiling functional languages and caused folks to turn away from this approach by customizing the combinator set to your particular program. Then Lennart Augustsson's work on implementing supercombinators more efficiently sealed the deal. GHC's compilation technique is a descendant of this school of thought.

But what did we give up to get to where we are? Let's explore a bit of alternate history.

Three years ago, I quit my job to bet everything on the proposition that Haskell could excel not just for specialized, high-assurance software, but for the kinds of software that millions of engineers work on every day. I had previously built backends with Haskell, with the wonderful experience of code that works reliably, a team that doesn't step on each others' toes, and an ease of refactoring that let us keep the codebase clean without risking regressions. But now, GHCJS and FRP had finally become reliable enough to trust in the real world. It was a game changer: Haskell could now build world-class graphical user interfaces, too, and deploy them as single page web apps — in theory.

In practice, there were many obstacles along the way. However, I found that even with the need to blaze new trails from time to time, our overall pace was far faster than anything I had seen in the imperative tech stacks I'd worked with before. Strong types and pure values decreased bug counts and made code much more readable. Some former backend developers who had scrupulously avoided frontend development told me that they now enjoyed working on the frontend, too.

Since then, I've worked with the community to continue building infrastructure to expand the areas where we can use Haskell to get real work done. Enabling mobile development required bug fixes to GHC, a rearchitected approach to cross-compilation in Nixpkgs, and bindings to native APIs. To scale up to larger projects, we've improved existing tools and created new tools that make developer workflows simpler, faster, and more discoverable. And to make Haskell app development more accessible to beginners and professionals without Haskell experience, we've made more and more functionality available out of the box.

In this talk, I'll show you the tools that are available today and the challenges that lie ahead. I hope you'll come away with a broadened understanding of how Haskell can be applied in your own professional projects — and how the theory of functional programming can be a potent practical tool.

Let's Lens presents a series of exercises, in a similar format to the Data61 functional programming course material. The subject of the exercises is around the concept of lenses, initially proposed by Foster et al., to solve the view-update problem of relational databases.

The theories around lenses have been advanced significantly in recent years, resulting in a library, implemented in Haskell, called lens.

This workshop will take you through the basic definition of the lens data structure and its related structures such as traversals and prisms. Following this we implement some of the low-level lens library, then go on to discuss and solve a practical problem that uses all of these structures.

Functional programming has become inevitable. New programming languages draw inspiration from the functional paradigm; old programming languages retrofit support for functional programming; and development teams change their coding style to adopt the best functional programming idioms. We are clearly experiencing a paradigm shift in our industry.

Due to its academic roots, functional programming sometimes seems unapproachable, with unfamiliar jargon, obscure concepts, and bewildering theories. It doesn’t have to be like that.

In this one-day series of lectures and hands-on workshops, we will translate the jargon, demystify the concepts, and put the theories into practice. There is nothing inherently difficult about functional programming. In fact, its main aim is to simplify programming and to make it more widely accessible. Functional programming is about being able to understand one function without the million lines of code it is a part of. It is about code reuse. It is about modularity and keeping code easy to change and refactor. These are all goals of good program design that every developer appreciates. Based on this common ground, we will explore functional programming together and see how it can help us to achieve these design goals. In fact, by learning the fundamentals of functional programming in Haskell, we can improve program design in mainstream languages, such as Javascript and C++, and even more so, in hybrid languages, such as Scala and Swift.

Throughout the day, we will explain the most commonly used functional programming terminology. You will learn the fundamentals of Haskell, one of the most popular functional programming languages. In the process, we will look at a lot of concrete code to understand what functional programming is all about and how to use it in your own programs. In the workshops, you will have plenty of opportunity to write code yourself, experiment, and ask questions. It’ll be fun!

Bring your laptop and your curiosity and by the end of the day, functional programming will be another tool in your toolbox, and you will be ready to enjoy the main YOW! Lambda Jam conference.