Lecture 40
Using Visitors
The visitor pattern allows the user to build a data structures so that
it is easy to add operations later.
Expression tree files
The following code provides the implementation of an expression tree that
supports visitors.
The following code provides an abstract class for a visitor as well as
implementations of visitors to perform interpretation of
arithmetic expressions along with visitors to perform
various ways of printing the
expressions.
Parser
This code builds the expression trees. We did not discuss it in class,
but it is needed to run the code
The following code is for an applet that creates a window to type in
expressions. The value is displayed in the applet and the results of
pretty printing in both inorder and postorder are displayed in the console
window.