codecrafters-lox-rust

Rust implementation of CodeCrafters's "Build your own Interpreter" Challenge.

This challenge follows the book Crafting Interpreters by Robert Nystrom. It involves building an interpreter for Lox, a simple scripting language.

Note

As of now (2024 Dec), the challenge only supports up to "Chapter 10 - Functions". Hence, this solution have not implemented Chapters 11~13 (Resolving and Binding, Classes, Inheritance).

Running

To run the Hello World program:

cargo run -- run examples/hello-world.lox

To learn more about the CLI:

cargo run -- --help

What's done differently?

This implementation deviates from the book in a few ways:

• The parser uses Pratt Parsing instead of Recursive Decent to parse expressions.
• Abstract Syntax Tree (AST):
  • Some AST nodes have slightly different names
  • Each AST node stores a Span that records the start and end positions of the source code.
• Evaluation:
  • For-loop desugaring is done at evaluation stage instead of parsing stage, so there is an AST node for for-loops.
  • Function call returns are handled using Rust's ControlFlow instead of "try-catch" approach.
• Error handling:

  • Errors are represented as enums instead of strings. A drawback is that the error messages are generic and does not match the book.

  • miette is used for pretty diagnostic printing. Only the tokenize command returns error messages in the book's format in order to pass CodeCrafters' tests.

    

Inspirations

These implementations greatly influenced the implementation:

• Implementing a Lox interpreter in Rust - Jon Gjengset
• Darksecond/lox
• jeschkies/lox-rs
• sagark4/rlox_ast_walk
• rami3l/dolores

Also huge thanks to Oxidation Compiler for their resources:

• JavaScript Parser in Rust
• Performance Optimization Tricks