Conver to using \ for member variables in classes. In structs just use the name.

fsm.hpp

@@ -12,17 +12,17 @@ template<typename S, typename E>
 class DeadSimpleFSM {
 protected:
   // BUG: don't put this in your class because state() won't work
- S _state = S::START;
+ S $state = S::START;
 
 public:
   template<typename... Types>
   void event(E event, Types... args);
 
   void state(S next_state) {
-    _state = next_state;
+    $state = next_state;
   }
 
   bool in_state(S state) {
-    return _state == state;
+    return $state == state;
   }
 };