What's Lox

Lox is a dynamically typed, interpreted script language, which is designed by Robert Nystrom for his book Crafting interpreters.

What's rustlox

A virtual machine(VM) for the Lox programming language implemented in Rust. The original book utilizes C to build the VM, referred to as clox. To maintain consistency, I chose the name rustlox for the Rust implementation.

Usage

# REPL
# debug build with debug info
$ cargo run

# execute a lox file
$ cargo run -- <file>

Benchmark

A naive benchmark in my MBP Intel i5-8257U @1.40GHz:

operations	Rust(-O)	Python 3.10.9	rustlox	PyLox
fib(35)	~ 0.03s	~ 3s	~ 8s	~ 600s

Notes

• 17.2 Parsing Tokens - Use std::mem::take to handle self.parser.previous = self.parser.current; and derive Default for the Token type.
• 17.6 A Pratt Parser - Impl a next associated function for the Precedence struct to get the next enum item.
• 18.1 Tagged Unions - Use enum instead of union, as the enum type is quite powerful in Rust.
• 24.4 Function declaration
  • Set a CompilerState field for the Compiler struct, which contains local variables, scope depth, function, enclosing, and function_type
  • Before compiling the function declaration, use std::mem::take to remember the old state and store it in the enclosing field