Erik Jonsson School of Engineering and Computer Science

1. Erik Jonsson School of Engineering and Computer Science CS 4384– 001 Automata Theory http://www.utdallas.edu/~pervin Tuesday: Context-Free Languages Chapter Three Thursday3-20-14 FEARLESS Engineering

3. Context-free Languages Chapter Three

6. Palindromes

7. Chomsky Normal Form

8. Other Simplifications Useful variables and productions Left-recursion

10. Useless Example

11. Left-recursion 3-04-14

14. Pushdown Automata Many similar definitions

15. STACK

16. 4. Cohen PDA

18. Odd Palindrome

19. Even Palindrome

21. CFG » PDA

22. PUMPING LEMMA Context-Free

25. NOTE: CFLs are not closed under intersection (or complement)!

33. Martin, P. 218; H&U, P. 115

34. I guess this is really Homework 12

35. Exactly like the regular problem!

37. CS 341 – UT-Austin

38. CS 341 – UT-Austin

40. Informal Verbal PDAs

41. Read and push a’s onto stack if any; read and ignore b’s if any; read and match c’s with stack exactly.

42. Read and push a’s onto the stack; read b’s and match them against the stack until empty; read any additional b’s and push them onto the stack; read and match c’s with stack exactly.

43. For each a read, non-deterministically push ONE or TWO a’s on the stack; then match b’s read exactly with stack.

49. Ambiguity Dangling ELSE Problem