v3 Language: Closures, Arrays, Maps

Why this module exists

We now cross the line into "real" language territory:

• nested functions with lexical scoping
• arrays and maps as heap objects
• indexed reads and writes
• runtime GC to manage memory

This is a different level of complexity, and that's the point.

1) Arrays and maps

Array literal:

let xs = [1, 2, 3];

Map literal (expression context):

let m = {"a": 1, "b": 2};

Map keys must be hashable: number, bool, string, or nil. Other key types are runtime errors.

2) Indexing and assignment

Read:

let v = xs[0];

Write:

xs[1] = 42;
m["a"] = 99;

Index assignment is a statement in this pack.

3) Nested functions + lexical scoping

Functions can appear inside blocks and return other functions:

fn makeAdder(x) {
    fn add(y) { return x + y; }
    return add;
}

The inner function captures x from its defining scope. This is lexical scoping.

4) Functions are values

Calls are allowed on any expression, not just identifiers:

let f = makeAdder(10);
let z = f(2);

5) Memory is real now

Arrays, maps, and closures live on a heap. The VM will use mark-and-sweep GC to reclaim unreachable objects.