cs230 Lecture Notes
Week 10 Monday

Exam Tomorrow!

Homework 7 solutions
--------------------

4 designs and their pros and cons


Array/Vector implementation of a tree
-------------------------------------



Using abstract class to improve encapsulation
---------------------------------------------

Tree does the traversal

A member of the Visitable abstract class defines what
it means to visit a node

Abstract class def'n  (in Visitable.java)

public interface Visitable {
    public void visit ();
}


Member class def'n   (in Token.java)

public class Token implements Visitable {
    String str;

    public Token (String str) {
        this.str = str;
    }

    public void visit () {
        System.out.print (str + " ");
    }
}


Abstract tree builder   (in Translator.java)

    String expr = "1 2 3 * +";
    StringTokenizer st = new StringTokenizer (expr, " +-*/", true);
    String token = st.nextToken();
    Tree tree = new Tree (new Token (token), null, null));


The infix generator is basically an inorder traversal of
the expression tree, except that it might have to insert
parentheses under certain conditions.