Extract the FSM before beginning to use it.

fsm.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+template<typename S, typename E>
+class DeadSimpleFSM {
+protected:
+  S _state = S::START;
+
+public:
+  virtual void event(E event) = 0;
+
+  void state(S next_state) {
+    _state = next_state;
+  }
+};
+
+#define FSM_T(S, F) case S: F(); break