Lykn

The Compiler

The compiler walks the reader’s tree and produces ESTree nodes. It’s a pattern-matching dispatch table in packages/lykn/compiler.js.

The Dispatch

The compiler’s core is a switch on the head atom of each list:

// Simplified — the actual code handles more cases
function compile(node) {
  if (isAtom(node)) return compileAtom(node);
  if (isString(node)) return { type: "Literal", value: node.value };
  if (isNumber(node)) return { type: "Literal", value: node.value };
  if (isList(node)) {
    const head = node.values[0].value;
    const handler = forms[head];
    if (handler) return handler(node.values.slice(1));
    return compileCall(node);  // default: function call
  }
}

Each kernel form has a handler function. The handler receives the arguments (everything after the head atom) and returns an ESTree node.

const → VariableDeclaration

(const x 42)

The handler produces:

{
  type: "VariableDeclaration",
  kind: "const",
  declarations: [{
    type: "VariableDeclarator",
    id: { type: "Identifier", name: "x" },
    init: { type: "Literal", value: 42 }
  }]
}

astring prints: const x = 42;

function → FunctionDeclaration

(function add (a b) (return (+ a b)))

Produces a FunctionDeclaration with Identifier params, a BlockStatement body containing a ReturnStatement with a BinaryExpression. The tree maps directly to ESTree — no transformation, no optimization, just structural translation.

Colon Splitting

When the compiler encounters an atom containing colons — console:log — it splits on : and produces a MemberExpression chain. Each segment gets camelCase conversion. document:get-element-by-id → document.getElementById.

Expression vs Statement

The compiler tracks context: is this form in expression position or statement position? A standalone (if ...) produces an IfStatement. An (if ...) inside a const initializer would be different. The surface compiler handles complex cases (IIFE wrapping for match), but the kernel compiler handles the basic context detection.