public:
  virtual void do_while_node(xpl::while_node * const node, int lvl) = 0;
  virtual void do_if_node(xpl::if_node * const node, int lvl) = 0;
  virtual void do_if_else_node(xpl::if_else_node * const node, int lvl) = 0;
  virtual void do_block_node(xpl::block_node * const node, int lvl) = 0;
  virtual void do_evaluation_node(xpl::evaluation_node * const node, int lvl) = 0;
  virtual void do_funciton_body_node(xpl::funcion_body_node * const node, int lvl) = 0;
  virtual void do_function_declaration_node(xpl::function_declaration_node * const node, int lvl) = 0;
  virtual void do_identity_node(xpl::identity_node * const node, int lvl) = 0;
  virtual void do_index_node(xpl::index_node * const node, int lvl) = 0;
  virtual void do_indexation_node(xpl::indexation_node * const node, int lvl) = 0;
  virtual void do_invocation_node(xpl::invocation_node * const node, int lvl) = 0;
  virtual void do_memory_reserve_node(xpl::memory_reserve_node * const node, int lvl) = 0;
  virtual void do_next_node(xpl::next_node * const node, int lvl) = 0;
  virtual void do_return_node(xpl::return_node * const node, int lvl) = 0;
  virtual void do_stop_node(xpl::stop_node * const node, int lvl) = 0;
  virtual void do_sweep_down_node(xpl::sweep_down_node * const node, int lvl) = 0;
  virtual void do_sweep_up_node(xpl::sweep_up_node * const node, int lvl) = 0;
  virtual void do_variable_declaration_node(xpl::variable_declaration_node * const node, int lvl) = 0;