Is it possible to swap two values at known indices?

[PartyWumpus]

If I was using a vec of vecs, this would be reasonably easy:

if they're in the same inner vec then just

arr.swap(index1, index2)

and if they're in different vecs then i can get a mutable reference to each and just

std::mem::swap(&mut value1, &mut value2)

I can't figure out a way to do this with the API you make available, even with std::ptr::swap