Vector with optional values - None or out of range?

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• If we have a vector that some of the elements can be None then the other elements must be Some-values and the whole thing must be defined using Option.
• If we try to access an element in a vector that is out of range we get a run-time panic.
• In order to avoid such panic we either need to check if our index is in range or we can use the get method.
• We can use the get method to access the element. It will return None if the index was out of range.
• Then the question arise, how do we know if the value was out of range or if it was in the range but the value was None?

examples/vectors/none-or-out-of-range/src/main.rs

fn main() {
    let numbers_real: Vec<Option<i32>> = vec![Some(3), None];
    println!("{:?}", numbers_real);

    println!("{:?}", numbers_real[1]); // None
    println!("{:?}", numbers_real.get(1)); // Some(None)
                                           // println!("{:?}", numbers_real[17]); // panic: index out of bounds: the len is 2 but the index is 17
    println!("{:?}", numbers_real.get(17)); // None    - out of range!
    println!();

    println!("{:?}", numbers_real.get(1).is_none());
    println!("{:?}", numbers_real.get(17).is_none()); // out of range!
    println!();

    println!("{:?}", numbers_real.get(1).is_some());
    println!("{:?}", numbers_real.get(17).is_some()); // out of range!
    println!();
}

[Some(3), None]
None
Some(None)
None

false
true

true
false