I don't think you need to abandon the S. I think FSMs embody the core of functional thinking. Structuring your computation as a FSM splits your code into your c

I don't think you need to abandon the S. I think FSMs embody the core of functional thinking. Structuring your computation as a FSM splits your code into your current state and a combinatorial logic block that takes a current state and outputs a new state along with some optional side-effects. Splitting your computations into pure functions that hold state on their end-points sounds very much like the philosophy behind FP.