Lox

Two implementations of the Lox Language, with my own modifications:

• rlox -> A tree-walk interpreter written in Rust
• zlox -> A bytecode virtual machine in Zig

An educational project made with the intention of learning about compilers and programming languages.

Referred books: Crafting Interpreters by Robert Nystrom

Features

• Dynamically typed
• Closures and first-class functions
• Classes with inheritance
• Dynamic lists with indexing
• Lambda expressions
• Static class methods and getters
• Ternary and loops and conditionals
• Number conversion and other helpful native functions

Examples

Closures

fun makeAdder(n) {
    return fun(x) { return x + n; };
}
var addFive = makeAdder(5);
print addFive(3);  // 8
print addFive(10); // 15

Lists and Higher-Order Functions

fun map(list, f) {
    var result = [];
    var i = 0;
    while (i < len(list)) {
        push(result, f(list[i]));
        i = i + 1;
    }
    return result;
}

var nums = [1, 2, 3, 4, 5];
var doubled = map(nums, fun(x) { return x * 2; });
print doubled; // [2, 4, 6, 8, 10]

Classes and Inheritance

class Shape {
    init(color) { this.color = color; }
    describe { return this.color + " " + this.name; }
    class create(color) { return Shape(color); }
}

class Circle < Shape {
    init(color, radius) {
        super.init(color);
        this.radius = radius;
    }
    name { return "circle"; }
    area { return 3.14159 * this.radius * this.radius; }
}

var c = Circle("red", 5);
print c.describe; // red circle
print c.area;     // 78.53...

Ternary

fun printShape(shape) {
    var kind = shape.area > 50 ? "large" : "small";
    print shape.describe + " is " + kind;
}

Recursion

fun fib(n) {
    if (n <= 1) return n;
    return fib(n - 1) + fib(n - 2);
}
print fib(10); // 55

Language Reference

The language isn't a 1:1 copy of the original Lox from the book, I have added various modifications of my own for convenience and challenge. For full grammar rules, native functions, and differences from the book see LANGUAGE.md.