title: "Lecture 6 - Regular Expressions and Closure Properties"
unit: 1
lecture: 6

Lecture 6 - Regular Expressions and Closure Properties

(Skeleton for Fall 2026.)

Closure Properties

TODO: union, concatenation, star, intersection, complement; the product construction; closure proofs as a reusable proof pattern.

Regular Expressions

TODO: syntax and semantics; equivalence with finite automata (both directions, GNFA construction sketch).

Using Closure to Prove Nonregularity

TODO: preview: combine closure with the pumping lemma from Lecture 7 to shortcut nonregularity proofs.