I'm trying to learn Antlr4 and working my way thru the examples in the Definitive Reference. All was going well until section 8.4.I can't complete the example in 8.4 (Validating Program Symbol Usage) due to missing *Scope.java and *Symbol.java files.I'm assuming that these are not Antlr-generated files and that they should be available on the https://media.pragprog.com/titles/tpantlr2/code/ site like other sources.