[clarkmoody]

In one version I've seen, the active element is of a different type, offering enhanced functionality over the vectors of next and prev items:

  struct List<T, A> {
    prev: Vec<T>,
    active: A,
    next: Vec<T>,
  }

This could be used for some active type that has ephemeral cache information or state associated with it (view state in a GUI app, for instance). The inactive type may be hydrated and converted to active, and the active type can be archived into an inactive type.