Pure functional programming is a powerful tool. With purity, we can reason through complex code by breaking it up into small composable parts.

But there are some areas that, despite being pure and functional, still puzzle us. In this talk, we’ll navigate the challenging currents of functional streams.

Beginning with basic pure functional programs, we’ll explore effects with cats-effect and concurrency with fs2. Along the way, we’ll encounter different frameworks for reasoning through code and build our own mental model of stream evaluation. We’ll see that functional streams, while inherently complex, are not as murky as they seem.