+ using cuptr = std::unique_ptr<const clock_class>;
+
+ virtual ~clock_class() = default;
+ clock_class(const clock_class&) = delete;
+ clock_class(clock_class&&) = delete;
+ clock_class& operator=(clock_class&&) = delete;
+ clock_class& operator=(const clock_class&) = delete;
+
+ virtual void accept(trace_class_visitor& visitor) const;