public void setAgg(NodeCursor<A, V> node, A a) {
assert (isAggValid(node));
aggstore.set(node.computeIndex(), a);
}
public A getAgg(NodeCursor<A, V> node) {
int index = node.computeIndex();
assert (index >= 0);
if (index < aggstore.size()) return aggstore.get(index);
return null;
}