`Option` and `Result`

The types represent optional data:

fn main() {
    let numbers = vec![10, 20, 30];
    let first: Option<&i8> = numbers.first();
    println!("first: {first:?}");

    let arr: Result<[i8; 3], Vec<i8>> = numbers.try_into();
    println!("arr: {arr:?}");
}

Option and Result are widely used not just in the standard library.
Option<&T> has zero space overhead compared to &T.
Result is the standard type to implement error handling as we will see on Day 3.
try_into attempts to convert the vector into a fixed-sized array. This can fail:
- If the vector has the right size, Result::Ok is returned with the array.
- Otherwise, Result::Err is returned with the original vector.