I've once implemented a regular expression engine based directly on https://en.wikipedia.org/wiki/Brzozowski_derivative https://en.wikipedia.org/wiki/Brzozowski

I've once implemented a regular expression engine based directly on https://en.wikipedia.org/wiki/Brzozowski_derivative https://en.wikipedia.org/wiki/Brzozowski_derivative – it's straightforward to implement both intersection and negation this way.