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0 pointspansa25mo ago0 comments

> the book's first half involves Java reflection

Does it? I know it uses metaprogramming (a Java program that outputs another Java program), but that’s probably easier in other languages than in Java. In my Python implementation I was able to significantly simplify that part of the code by using `eval`.

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scuff3d4mo ago

Yeah I don't recall reflection either.

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.

Regardless, the book is incredible, and the choice of Java to start with makes sense. Its probably going to be the most universally approachable for everyone, even if they aren't super familiar. C can be pretty overwhelming if you aren't familiar it.

pansa2OP4mo 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.

scuff3d4mo 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.

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scuff3d4mo ago

Yeah I don't recall reflection either.

pansa2OP4mo ago

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

scuff3d4mo ago

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

1 more reply

j / k navigate · click thread line to collapse