====== Homework 4 ======
//Out: 30 Nov 2008, Due: 8 Dec 2008//

  - Problem 1.64a
  - Exercises 2.1, 2.4(b,c,e,f), 2.8, 2.12, 2.15, 2.17
  - Problem 2.31
    * Hint: consider 1<sup>p</sup>0<sup>p</sup>0<sup>p</sup>1<sup>p</sup>
  - Bonus: Problem 2.20
    * Hint: Let //P// be a pushdown automaton that recognizes //A// and //D// be a DFA that recognizes //B//.  A pushdown automaton //P//' that recognizes //A/B// consists of essentially two components, one for recognizing the first part //w// and another that simulates the string //x//.  The harder one to design is the second component.  Try to use nondeterminism (e.g., epsilon moves) to simulate //P// that works with **non-existing** string //x// while tracking the states of //D//.
  - Bonus: 1.60, 1.61