I am not convinced current interpolation techniques cover what Jt0 is looking for. I think addr:interpolation only deals with house numbers not with apartment numbers.

Maybe you need to give a more concrete example, Jt0, but I understand that you have a situation like this:

A Street:
1st building: apartments 1-20
2nd building: apartment 21-40
3rd building: apartment 41-60

B Street:
4th building: apartments 1-15
5th building: apartments 16-30

Now you would like to be able to search for B Street apartment# 12 and be directed to the 4th building. Is that correct? No classical house numbers involved (do they exist additionally?).

I have no clue how to do that without mapping each individual apartment or relying on some search application to eventually cater for searching within a range.