COMS W3261
Computer Science Theory
Lecture 5:September 19, 2012
Pumping Lemma for Regular Languages

Overview

1. Algebraic Laws for Regular Expressions

2. The Pumping Lemma for Regular Languages

3. Practice Problems

  1. Show that the language consisting of all strings of balanced parentheses is not regular.
  2. Prove that the language consisting of all strings of a's and b's that read the same forwards as backwards is not regular.
  3. Prove that the language L = { w | w = aibj where i is not equal to j } is not regular.

4. Reading Assignment



aho@cs.columbia.edu