You mean because they don't consider combinators for parsing? That's the only example I can think of for higher order functions used in compilers. Combinators

You mean because they don't consider combinators for parsing? That's the only example I can think of for higher order functions used in compilers. Combinators are much more powerful (though less efficient) than the construction of automata (which the Dragon book covers). I'm implementing parser combinators with some unusual properties at the moment, and then (hope to!) prove some things about them. I wish the Dragon book had covered this approach in the first place. So your comment is relevant to me.