1. Building AST's for RPAL Programs
Programming Language Concepts
Lecture 14
Prepared by
Manuel E. Bermúdez, Ph.D.
Associate Professor
University of Florida

2. Let's Build a Few Abstract Syntax Trees
Example 1: Factorial, version 3.
Example 2: Palindrome.
Example 3: Add numbers from list.
Example 5: Build tuple of pairs of characters.

7. Class Project Build a recursive descent parser for RPAL (gulp!)
If done properly, it's easy.
Need lexical analyzer, to be called repeatedly (important!) by the parser. Avoid scanning the entire input in advance of the parser.

8. Class Project (cont’d)
Code up one procedure per nonterminal in RPAL's grammar.
Pseudo code for some portions of RPAL’s grammar

12. Class Project (cont’d)
Implement support module for trees, and stack of trees.
Suggestion: use first-child, next-sibling binary tree representation of n-ary trees (it works!).
Preorder traversal of this tree is the same as for n-ary tree.
Popping n trees from the stack, and building a parent node on top of them, is easy.

15. Building AST's for RPAL Programs
Programming Language Concepts
Lecture 14
Prepared by
Manuel E. Bermúdez, Ph.D.
Associate Professor
University of Florida