// ===========================================================
//  Bob feature-tour demo
//  – dot-notation for dictionaries & arrays
//  – property assignment (incl. nested)
//  – built-in properties:  dict.keys / dict.values
//                          arr.length / arr.first / arr.last / arr.empty
//  – tail-call-optimised (TCO) recursion
// ===========================================================

// ---------- 1. Dictionary property access / assignment ----------
var person = { "name": "Alice", "age": 30 };
print(person.name);
print(person.age);

// add a brand-new user property
person.country = "Canada";
print(person.country);

// nested property assignment
var team = { "lead": { "name": "Bob", "age": 40 } };
team.lead.age = 41;
print(team.lead.age);

// built-in dictionary properties
print("dict length = " + team.length);
print(team.keys);
print(team.values[0].name);

// ---------- 2. Array dot-properties ----------
var nums = [ 10, 20, 30, 40 ];
print("len = " + nums.length);
print("first = " + nums.first);
print("last = " + nums.last);
print("empty? " + nums.empty);

// dot-properties are read-only; assignment still via index
nums[0] = 99;
print(nums.first);

// ---------- 3. Tail-call-optimised recursion ----------
func fibTail(n, a, b) {
    return n <= 0 ? a : fibTail(n - 1, b, a + b);
}

print("Fast TCO fib(90) = " + fibTail(90, 0, 1));
print("Fast TCO fib(5000) = " + fibTail(5000, 0, 1));

// ---------- 4. Compare non-TCO version (stack grows!) ----------
func fibPlain(n) {
    return n <= 1 ? n : fibPlain(n - 1) + fibPlain(n - 2);
}

print("Slow recursive fib(35) = " + fibPlain(35));

// ---------- 5. Summary ----------
print("All new features demonstrated!");