Finite state machines are simple and so useful!
Check out Noel Welsh's talk from Scala Love in the City Conference where you'll see why finite state machines should be be widely used.
Finite State Machines for Functional Software Machinery
Finite state machines (FSMs) are one of the simplest models of computation, but it’s this simplicity that makes them so useful. They are expressive enough to cover a wide range of practical problems while remaining easy to reason about. I believe they should be more widely used, and the only reason they aren’t is because many developers only know them in the context of a dusty theory of computation course. This talk sets out to change this!
I’ll first (re)introduce finite state machines as a model of computation. I’ll show that they are very simple, which makes them easy to understand and therefore create and debug. We’ll then see how finite state machines appear just about everywhere. We’ll see examples in the Scala standard library, and in application code from web services and user interfaces. We’ll finish by discussing implementation techniques and further applications.