Method add_dependency

lib/yamlcpp/include/yaml-cpp/node/detail/node.h:56–61

  }

  void add_dependency(node& rhs) {
    if (is_defined())
      rhs.mark_defined();
    else
      m_dependencies.insert(&rhs);
  }

  void set_ref(const node& rhs) {
    if (rhs.is_defined())