Interesting. I was familiar with Missing and nothing in Julia but had never really thought about other options from a safety angle. It makes sense though. I ha

Interesting. I was familiar with Missing and nothing in Julia but had never really thought about other options from a safety angle. It makes sense though. I have run into issues where it would be nice to have some sort of missing type/class hierarchy though, in that the reason for missingness is coded somewhere and then how to represent that in those three categories gets complicated. At some level the different missing types get treated the same for many functions (such as your missing + 1 propagation example) but for other things not. Then you end up being tempted to use the third option which has its own issues. I suppose you could create another variable with type of missing information but then that also becomes complex quickly.