The type is akin to optional<int>. You can't add 5 to it, you have to dereference it first which crashes if it was null (0 or another chosen value).

Well, in Rust you would use pattern matching, which can't even crash.

In Haskell, the closest thing to adding 5 to an optional value would be something like:

    fmap (5+) my_optional_value

This one leaves 'Nothing' alone, but adds 5 in case the value is present.