Programs are getting fat. They're becoming slow. They're taking up more computing resources. They're getting harder to maintain and more complex from the ground up. Layer upon layer of sophistication is causing us to lose our ability to predict what software will do. Where's that bug? Why is everything going so slowly? Am I even using the right data structures? Where's that important point in the documentation again?

What's happened to us? In this meta-dive into the nature of our approach to programming, we will explore some of the dangers of our current approaches to programming and the how/why of our current programming obesity problem. We will look at real case studies and see just how bad the situation can be.

But we will also explore how we can battle these sources of obesity. In this passionate plea for code that we can gain control over again, we will look at examples of how we can return to a state of high-performance on all levels, from code size to code scalability. We will look at the principles that can help us to reach leaner, more efficient, more usable, less buggy code. We will hopefully find some light at the end of the tunnel, and how we can change our outlook on programming to push ourselves towards code that benefits not only ourselves, but also those that will come after us.

This full day workshop will focus on applying Haskell to normal, everyday programming. We'll be focusing on getting comfortable with common tasks, libraries, and paradigms, including:

• Understanding strictness, laziness, and evaluation
• Data structures
• Structuring applications
• Concurrency and mutability
• Library recommendations

By the end of the workshop, you should feel confident in working on production Haskell codebases. While we obviously cannot cover all topics in Haskell in one day, the goal is to empower attendees with sufficient knowledge to continue developing their Haskell skillset through writing real applications.

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.