[galangalalgol]

As another comment below points out, any non trivial software contains FSMs but they can express it in any number of ways. Haskell trying to avoid mutable state would probably pass around a constant data structure recursively through a series of pure functions. I find explicit FSMs difficult to reason about and find pure functions operating on complicated data structures much easier to reason about. It is irrational to conclude there is one clearest representation for everyone even within a single problem space. Experiment, find the one that suits you and show understanding to those who think and learn in other ways.

[ArkyBeagle]

The mechanism for learning to think in state machines is message sequence charts. For each state there is usually a short list of Things That Can Go Wrong ( timeout, race condition, garble, inappropriate message ).

Ya gotta think like a clockmaker.

[im_down_w_otp]

Erlang is doing exactly what you're saying here.