Aren't specialized lexer/parsers finite state machines? As are encoder/decoders? OK fir complex computation, I left the world of mathematics 7 years ago, and I

Aren't specialized lexer/parsers finite state machines? As are encoder/decoders? OK fir complex computation, I left the world of mathematics 7 years ago, and I wasn't at the edge on that, I trust you, but to be clear, all your examples scream 'FSM' to me. If you have a pattern matching routine of 50+ lines that isn't a finite state machine, you're doing something wrong imho, and should consider changing abstraction (I'm not a big OO guy, but maybe use dynamic dispatch?)