[munificent]

> but a modern main stream language that can avoid code generation and Visitor Pattern.

Yeah, a language with nice algebraic datatypes and pattern matching does eliminate the need for Visitor patterns.

But the reality is that many programmers are working in object-oriented languages where the Visitor pattern is useful, so I deliberately picked Java in order to teach that approach. The book tries to meet you where you are and not where you might wish you were.