STL list的erase实现
iterator erase(iterator position) {
link_type next_node = link_type(position.node->next); link_type prev_node = link_type(position.node->prev);
prev_node->next = next_node; next_node->prev = prev_node;
destroy_node(position.node);
return iterator(next_node);
}
iterator erase(iterator first, iterator last);