node = node.succ();
      }
    } else {
      node = header.succ();
    }
    return (node == header || !range.contains(node.getElement())) ? null : node;
  }

  private @Nullable AvlNode<E> lastNode() {
    AvlNode<E> root = rootReference.get();
    if (root == null) {
      return null;
    }
    AvlNode<E> node;
    if (range.hasUpperBound()) {

	errCmpInvalidBoolOperator = errors.New("invalid comparison operator for boolean arguments")
)

// Value represents a value of restricted type reduced from an
// expression represented by an ASTNode. Only one of the fields is
// non-nil.
//
// In cases where we are fetching data from a data source (like csv),
// the type may not be determined yet. In these cases, a byte-slice is
// used.
type Value struct {