Evaluating Expressions

2023-07-20

Today, I created functionality to parse and evaluate prefix expressions in my math language. To parse, I created an ExpressionParser class that only has one public method and a couple private ones. The public method is String[] getTokens(String input) and it converts a string like "(+ 23 9)" into an array of strings like ["(","+","23","9",")"], this way it is easier to evaluate expressions which is what I created the functionality for next. To evaluate expressions, I made a hierarchy of ExpressionNodes like so:

Then, to construct the tree of nodes, I just loop through the tokens and create a new node based on what the token is. When the tree is constructed, all I have to do to evaluate it is call evaluate() on the root node.