12. The NFA Engine

• NFA stands for "Non-Deterministic Finite Automaton".
• (PS. Yes, because it's no longer "deterministic", mathematically [apparently] that means that we are not using a "regular" expression anymore! That's why you'll somtimes see them called "nonregular expressions").
• An NFA regex engine is sometimes called a "regex directed" engine, because this time, it's the regex that controls the way it matches.
• This is the engine that looks like our simplified example engine - it starts at the first character in the target string, and then it tries to match the regex - and if it fails, it bumps along to the next character, backtracking through the regex when required.
• Let's look at the same example as last time, but this time with an NFA engine.