Kinda? It’s a very specific sort of the kind of thing I’m thinking of, but it doesn’t “solve” the general case.
Basically I find myself frequently wanting to enumerate two kinds of lists: all the stuff that would be affected by some Action in some situation; and more or less the equivalent of an in-game grep–go through a list of objects in scope and apply a filter.
And coding this sort of thing from scratch isn’t a huge challenge…it’s just that these sorts of things seem so foundational that I wonder if they might already be implemented somewhere that I’m just missing. So I’m asking to avoid re-inventing the wheel.