Lykn

What You’ll Need for This Book

The Essentials

To follow along with the examples in this book, you need:

• The Lykn compiler — a single Rust binary, built as described in the installation section above
• A JavaScript runtime — Deno, Node.js, or Bun, to run the compiled output. This book uses Deno in its examples.
• A text editor — any editor that can save a file with a .lykn extension. Lykn files are plain text. If your editor supports Lisp or Scheme syntax highlighting, enable it — the parenthesis matching alone is worth it.

That’s the list. There is no build system to configure, no package.json to maintain, no node_modules to summon from the void. The compiler is a self-contained Rust binary. The output is JavaScript with no dependencies.

What You Should Know

This book assumes you know what a variable is, what a function does, and that computers exist. Beyond that, it assumes remarkably little.

If you have JavaScript experience, you will find familiar ground quickly — every Lykn concept maps to a JavaScript concept, and this book points out the mapping at every step. Every chapter draws on material from Exploring JavaScript, Deep JavaScript, Eloquent JavaScript, and JavaScript: The Definitive Guide to ensure the JavaScript side is covered with depth and precision.

If you’re new to JavaScript, this book teaches it. You will learn JavaScript’s scoping rules, its type system, its prototype chain, its module system, and its async model — but you’ll learn them through Lykn’s lens, which has the advantage of making the dangerous parts visible and the safe parts default.

If you have Lisp experience, you will feel at home with the syntax and occasionally startled by the vocabulary. Lykn uses bind where you expect def, func where you expect defun, and fn where you expect lambda. The reason — short English words over traditional abbreviations — is a deliberate design choice. The parentheses, at least, are exactly where you left them.

Editor Support

There is no dedicated Lykn editor plugin yet. For now, configure your editor’s file associations to treat .lykn files as Scheme or Common Lisp. This gives you parenthesis matching, rainbow delimiters (if your editor supports them), and reasonable indentation. The keyword syntax (:string, :args) won’t highlight perfectly, but the structural editing — the part that actually matters when writing s-expressions — will work.