My experience crafting an interpreter with Rust (2021)

Is the first half of the book boring or is it just me?

I wasn't really expecting the scanner/lexer to be interesting, but the interpreter part as well feels like an absolute slog. I started with a lot of enthusiasm but just couldn't keep going after implementing functions. I downloaded someone else's JsLox implementation and was planning on just skipping to the VM part of the book and hopefully would find it more engaging.

I also am a pretty jr developer. I have about 5 years experience since I started learning to code so I just may not "get" it yet. But I found writing the interpreter to be incredibly boring.

It does take time and effort to really internalize these rules. But eventually you should be able to have a mental model of how ownership and borrowing work; consider what owns the data, if it can be borrowed within statically known scopes, will it need to mix sharing and mutation, and then apply Rust-specific types and design patterns to match.

Conversely, there are things that you just can't do, like using temporary references for parent-child relationships. Knowing this will save you time from even trying.

Perhaps learning materials need to be more explicit about it. For example, I suspect lots of people are discovering the limitation of self-referential structs the hard way.

I suspect if you could use UNION better and be the same as Enum in Rust you could do us a favor! Also I wish I could do this easily:

    enum Tag {
        Int,
        Bool
    }

    enum Data {
        Int(Vec<i32>),
        Bool(Vec<bool>)
    }

    struct Val {
        tag:Tag,
        data:Data
    }

    let n = val.as_i32::<Tag::Int>(&self) -> Vec<i32>

  outer: loop {
    loop {
      let res = self.interpreter_loop(…);
      match res {
        Continue => {}
        Return => { break 'outer; }
        Exception => { break; }
      }
   }

If you weren't going to expose clox to the web or other untrusted input (and why would you), it's not a concern.

You definitely don't need any expert knowledge though! Also following the book will increase your C knowledge as you go (at least in the second half).