[sebastos]

Huh, yeah I see. I guess I work more on the robotics side where messages often contain physical or geometric quantities, and that colors my thinking a bit. So "distance to that thing = 0" is a very possible situation, and yet you also want to allow it to say "I didn't measure distance to that thing". And those are very distinct concepts you never want to conflate.

[hot_gril]

I can see that. Or the rare situations where I needed 0 vs null, if for some reason that situation was multiplied times 100, I'd start wanting an optional keyword.