CSCI 310 Spring 2005, Day 16

1. Administrivia
   • gary leaves town Wed. night, gone until Sunday. demo target monday.
   • "class" not a valid token name for use in productions.

2. Questions on project 3, hw 2?

3. Abstract Syntax Trees
   1. [insert prayer that cygwin works on 223 machine] let's look at the parse tree for the simple 3.30 grammar.
   2. What parts of the tree nodes are actually necessary to keep around? (e.g. if I know it's a while node, do I need to keep the while token?) Are there aspects of the parse tree that were necessary for parsing but not necessary afterwards?
   3. An abstract syntax tree is an abstract representation of the parsed program, free of the unnecessary pieces of syntax and grammar structures. It provides a clean interface to think about semantic issues.
   4. grammar 3.30 can be simplifed a bit and serves to show how we can convert concrete parse trees to ASTs in sable.