Klox

A Kotlin implementation of the Lox programming language from Robert Nystrom's Crafting Interpreters.

Expedition Disclaimer

I'm acclimatizing to the terrain and unfamiliar with the equipment. If you notice me doing something dangerous, shout a warning (or open a PR)!

No TDD, I know... Following the book's structure, learning interpreter concepts together with Kotlin for now. I will practice TDD for a second implementation, perhaps with Thorsten Ball's Writing An Interpreter In Go.

Quick Start

Coming up.

What Works

• Variables and arithmetic: Declare variables, do math, concatenate strings
• Control flow: if/else, while, for loops
• Logical operators: and, or with short-circuiting
• Scoping: Block-level variable scopes
• REPL: Interactive prompt with persistent state
• Native functions: clock() returns current time

What Doesn't Work Yet

Functions are partially implemented (parsing works, execution doesn't).

Example Code

Variables and arithmetic:

var a = 10;
var b = 20;
print a + b; // 42

Control flow:

var x = 5;
if (x > 3) {
    print "x is big";
} else {
    print "x is small";
}

Loops:

var i = 0;
while (i < 5) {
    print i;
    i = i + 1;
}

Functions:

fun fibonachos(n) {
    if (n <= 1) return n;
    return fibonachos(n - 2) + fib(n - 1);
}

print fibonachos(10);

Architecture

Three-stage pipeline:

1. Scanner: Source code → tokens
2. Parser: Tokens → AST
3. Interpreter: AST → execution

Entry point: Main.kt handles REPL and file execution.