private void invalidateHelper(Hashable hashable, Token pleft, Token t) {
hashable.hash(null);
if (hashable instanceof Leaf) return;
// else: node.
Inner node = (Inner) hashable;
if (Range.contains(pleft, node.token, t))
// left child contains token
invalidateHelper(node.lchild, pleft, t);
else
// right child contains token
invalidateHelper(node.rchild, node.token, t);
}
/** Invalidates the ranges containing the given token. */
public void invalidate(Token t) {
invalidateHelper(root, partitioner.getMinimumToken(), t);
}