What I think you are saying is “You can’t do that because the OP wants the set of things which are considered ‘null’ to be the empty set’.” And I’m saying: Julia provides us with objects which are specifically intended to be considered “null”, so why not take one of those as the only element in the set of things which should be considered “null”?
I only bother to mention it because (at least in my experience) it’s not a common practice for a package to provide (as output) arrays containing undefined references and expecting someone to handle that, but it is not so unusual for them to provide arrays contianing nothing or missing.
Of course, I have no idea what the OP is trying to do, so I don’t know what the appropriate choice is here.
No I didn’t. I said that you shouldn’t (edited…) consider everything about “leaving undefined references in your array” being “bad practice” (that’s what I specifically replied to). I never once mentioned what he want since he didn’t mention and I don’t want to guess. I’m only saying that you shouldn’t just see undefined reference and claim they should all be replaced by missing or nothing and I even agree that unless you need to handle Any (i.e. all types) missing or nothing could be fine.