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pansa2 3 days ago  [ - ]

> I do remember him using the visitor pattern to implement part of the parser I think. I thought that was kind of an odd choice, especially since it seemed like he was really just trying to avoid Java boilerplate.

It's used to allow writing a "resolver" and an "interpreter" that both know how to handle every type of node in the AST. It's almost a functional approach, and I actually think it might increase boilerplate because Java is more designed around the object-oriented approach of adding `resolve` and `interpret` methods directly to each node type.

The two approaches result in very different code organisation, though - maybe the visitor approach was easier to explain in prose.

scuff3d 2 days ago  [ - ]

It's been a while since I read it, but I remember him saying something about the more natural (my word not his) approach being a single data structure that you would pass through both components, but he didn't want to do that because Java doesnt really encourage that kind of design, and you have a bunch of boilerplate for each class. It just struck me as an odd choice since the book was more about compiler/interpreter fundamentals, and I feel like the visitor pattern is a bit in the weeds in terms of OOP design.

I wonder if he wrote today if he would have used a Record and done the more straightforward implementation.

nogridbag 2 days ago  [ - ]

I went through the Crafting Interpreters book with modern Java. I posted this on reddit, but I basically used records and sealed interfaces. With modern Java there's no need for visitor pattern.

    private void execute(Stmt statement) {
        switch (statement) {
            case Stmt.Expression expression -> evaluate(expression.expr());
            case Stmt.Block block -> executeBlock(block.statements(),
               new Environment(environment));
            ...

    public sealed interface Expr permits
        Expr.Assign,
        Expr.Binary,
        Expr.Call,
        Expr.Function,
        .... more exprs here
scuff3d 2 days ago  [ - ]

Interesting. Almost all my actual experience writing Java is in Java 8, so I'm not super familiar with the modern stuff (other then a few things like Records). I'll have to take a look.

Most of the people I know who write Java would have an aneurysm at seeing a switch statement.

To be clear, that's a critique of the Java mindset, not your code. Lol