Function operator()

cpp/src/parquet/arrow/path_internal.cc:579–581

    PathInfo::Node& node = path_info->path[stack_position - stack_base];
    struct {
      IterationResult operator()(NullableNode& node) {
        return node.Run(stack_position, stack_position + 1, context);
      }
      IterationResult operator()(ListNode& node) {
        return node.Run(stack_position, stack_position + 1, context);
      }