the elements by 'score', with the actual value being the key. On the other
side the type also takes an hash table with key->score mapping, so that when
there is an update we lookup the current score and can traverse the tree.
the elements by 'score', with the actual value being the key. On the other
side the type also takes an hash table with key->score mapping, so that when
there is an update we lookup the current score and can traverse the tree.