iPad Notes: https://www.eecs.yorku.ca/~jackie/teaching/tutorials/notes/EECS4302%20Tutorial%20on%20ANTLR4%20Parser%20Generator.pdf
- AntlrExampleVisitor Project
- Adding semantic actions (effectively a visit method) to each production alternative
- Re-generate the Java files
- Reuse most of the model classes in `expression` package
- Retrieving model Expression object directly from the parser (no visit)
- Set up Run Configuration in Eclipse (file prompt) and run test cases on the console
- Export project as an executable JAR and run test cases on the command line prompt
- Comparison: Visitor vs. Action
