> How does this AoVA data structure work in practice? Don't you lose index-based access, in the sense that arithmetic on indices is potentially no longer meanin

> How does this AoVA data structure work in practice? Don't you lose index-based access, in the sense that arithmetic on indices is potentially no longer meaningful in the array sense? Iteration will not preserve insertion order. The caption to figure 4 suggests that the AoVA pattern is not a good fit if you need to retain the full order of inserted elements: > Compared to the SoA layout from before, we have a partial order instead of a total order. So upon insertion, we get back a tagged index that holds both the enum tag and the index in the particular variant array. So by my reading, ordered access is considered out of scope here. (I suppose you could recover ordered iteration by storing a global index in each element, but that still wouldn't help with ordered random access, and it would likely lead to some really branchy code.)