I've been looking into EC. There are definite similarities to what I've been
discussing, but I haven't come across population virtualisation yet. I've also
checked out permutation trees in the literature and they're not what I'm doing.
So I suppose it's best to keep it nameless for now. It's not specific to integers,
but using integers makes it handier to use. It could just as well represent the
variation of individuals in a GP population.