1. Top-Down parsing LL(1) parsing

2. Overview of Top-Down  There are only two actions 1.Replace 2.Match

3. Overview of Top-Down  e.g. with grammar

4. LL(k) parsing  L stands for left-to-right parse of input  L stands for leftmost-derivation  k stands for k-token look-ahead

5. LL(1) Parsing  At top of Parsing stack  For Non-terminal  Replace: a decision must be made, based on the current input token.  For terminal  Match: no decision is to be made but need to see if it is the same as the current input token, if not, an error occurs.

6. LL(1) Parsing : First Sets  First Sets  Let X be a grammar symbol (a terminal or non-terminal) or ε. Then the set First(X) consisting of terminals, and possibly ε, is defined as follows

7. LL(1) Parsing : First Sets  e.g. for the grammar

8. LL(1) Parsing : Follow Sets  Follow Sets  Given a non-terminal A, the set Follow(A), consisting of terminals, and possibly $, is defined as follows.  ε is never an element of Follow set

9. LL(1) Parsing : Follow Sets  e.g. for the grammar

10. First & Follow set Non-terminalnullableFirstFollow SYes($, )

11. LL(1) Parsing table  How to construct LL(1) parsing table

12. LL(1) Parsing table M[N,T]()$ S(S)Sεε

13. LL(1) Parsing table M[N,T]()$ S(S)Sεε

14. LL(1) grammar  A grammar is LL(1) if the following conditions are satisfied.  That is the LL(1) parsing table has at most one production in each table entry.

15. Mentioned issues  Left Recursion removal  Left Factoring

16. References  COMPILER CONSTRUCTION: Principles and Practice,  Kenneth C. Louden  Chapter 4  http://www.cs.sjsu.edu/faculty/louden/cm ptext/ http://www.cs.sjsu.edu/faculty/louden/cm ptext/ http://www.cs.sjsu.edu/faculty/louden/cm ptext/  http://www.course.com/isbn=0-534- 93972-4 http://www.course.com/isbn=0-534- 93972-4 http://www.course.com/isbn=0-534- 93972-4