I was wondering the same thing, so I ran a little experiment to understand how that's working:

func recursiveArray(num: Int) -> [Int]? {
  guard num > 0 else { return nil }
  print([num])
  return [num] + (recursiveTest(num: num - 1) ?? [0])
}
print(recursiveTest(num: 10)) // Optional([10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0])

When I run this with an input of 10, the print statement on line 3 produces a series of numbers counting down from 10, each in an array (i.e. [10], [9], and so on). The final iteration returns nil, which is triggered by the guard statement in line 2, which allows the recursion to stop running. It is the exit mechanism. I hope that helps.

Hi, I'm using Swift and I get a "exit code 132" when I run the attempt. No problem at all with the running the sample tests. There is no information provided on what is causing the issue. Any ideas?