insert (IntervalSkipList)

    # File lib/treetop/runtime/interval_skip_list/interval_skip_list.rb, line 40
      def insert(range, marker)
        ranges[marker] = range
        first_node = insert_node(range.first)
        first_node.endpoint_of.push(marker)
        last_node = insert_node(range.last)
        last_node.endpoint_of.push(marker)

        cur_node = first_node
        cur_level = first_node.top_level
        while next_node_at_level_inside_range?(cur_node, cur_level, range)
          while can_ascend_from?(cur_node, cur_level) && next_node_at_level_inside_range?(cur_node, cur_level + 1, range)
            cur_level += 1
          end
          cur_node = mark_forward_path_at_level(cur_node, cur_level, marker)
        end

        while node_inside_range?(cur_node, range)
          while can_descend_from?(cur_level) && next_node_at_level_outside_range?(cur_node, cur_level, range)
            cur_level -= 1
          end
          cur_node = mark_forward_path_at_level(cur_node, cur_level, marker)
        end
      end