<@U280UQQNA> : yes, that would work. Essentially ...

# getting-started

[nkiesel]

@gjesse : yes, that would work. Essentially that is what I started with (using null instead of an explicit Invalid). I agree that an explicit "invalid" is better than using null, but of course also more code to write. And would still produce a new list with many elements and then throw most of them away in the next step (in the extreme case that most elements would be invalid), which I tried to avoid.