Slides for my talk at Scala Italy 2019, in Bologna. You can look at them online at https://systemfw.org/scala-italy-2019/#/ (use the spacebar to advance). Video coming soon. Have a look at Examples.scala for the code.
fs2 and cats-effect offer a very powerful and composable set of concurrent combinators and data structures, which are all built out of two deceptively simple primitives: Ref and Deferred.
This talk will explain what they are, the design principles behind them, and how to use them to build your own business logic abstractions. In the process, we will discover a general pattern in the form of concurrent state machines, and see how it integrates with final tagless on one hand, and streaming control flow on the other.