10. The DFA Engine

• DFA stands for "Deterministic Finite Automaton".
• A DFA regex engine is sometimes called a "text directed" engine because it is the text that is being searched, as opposed to the regex, that directs the matching.
• The way this works is that the characters in the text being searched are looked at one at a time, in order, and any potential matches in progress, or completed potential matches, are tracked in parallel.
• Yes, this seems to be completely different to the way I was describing how our simplified regex engine worked in the previous slides - that's because the simplified engine was based on the NFA engine - and we'll get to that shortly.
• Let's take a look at an example and work through it using the DFA engine.