print("\n--- Test: Extension methods on built-ins ---");

extension array {
  func sum() {
    var i = 0;
    var s = 0;
    while (i < this.len()) {
      s = s + this[i];
      i = i + 1;
    }
    return s;
  }
}

extension dict {
  func size() { return this.len(); }
}

extension string {
  func shout() { return toString(this) + "!"; }
}

extension any {
  func tag() { return "<" + type(this) + ">"; }
}

assert([1,2,3].sum() == 6, "array.sum should sum elements");
assert({"a":1,"b":2}.size() == 2, "dict.size should return count");
assert("hi".shout() == "hi!", "string.shout should append !");
assert(toInt(42).tag() == "<number>", "any.tag works on numbers");
assert("x".tag() == "<string>", "any.tag works on strings");

print("Extension methods on built-ins: PASS");