50.8 Option exercises

50.8.1Returning an Option¶

We define foo() as a function that takes a usize as argument and returns an Option<bool>. If the indices is out-of-bound, we return a None value:

:clear

fn foo(i: usize) -> Option<bool> {
  let arr = [true, false, true];
  if i >= arr.len() {
    None
  } else {
    Some(arr[i])
  }
}

Here are the results for indices from 0 to 4:

(foo(0), foo(1), foo(2), foo(3), foo(4))