exception BadInput
{
  string message;
};

abstract interface base
{
  string base_op (in string inarg)
    raises (BadInput);
};

interface foo : base
{
  string foo_op (in string inarg)
    raises (BadInput);
};

interface passer
{
  void pass_ops (out base outarg);
  void pass_state (out base outarg);
  void pass_nil (out base outarg);
  oneway void shutdown ();
};

valuetype BaseNode
{
  public BaseNode left;
  public BaseNode right;
};

valuetype StringNode : BaseNode
{
  public string name;
};

valuetype TreeController supports base
{
  public BaseNode root;
};