public void SetUnop(PUnop node)
        {
            if (_unop_ != null)
            {
                _unop_.Parent(null);
            }

            if (node != null)
            {
                if (node.Parent() != null)
                {
                    node.Parent().RemoveChild(node);
                }

                node.Parent(this);
            }

            _unop_ = node;
        }
 internal override void RemoveChild(Node child)
 {
     if (_unop_ == child)
     {
         _unop_ = null;
         return;
     }
     if (_exp_ == child)
     {
         _exp_ = null;
         return;
     }
 }
 public AUnopExp(
         PUnop _unop_,
         PExp _exp_
 )
 {
     SetUnop(_unop_);
     SetExp(_exp_);
 }