auto | requires_ (detail::as_cref_t< T > t, detail::as_cref_t< U > u) -> decltype(concepts::valid_expr(concepts::model_of< WeaklyOrdered, T >(), concepts::model_of< WeaklyOrdered, U >(), concepts::model_of< CommonReference, detail::as_cref_t< T >, detail::as_cref_t< U >>(), concepts::model_of< WeaklyOrdered, C >(), concepts::convertible_to< bool >(t< u), concepts::convertible_to< bool >(u< t), concepts::convertible_to< bool >(t > u), concepts::convertible_to< bool >(u > t), concepts::convertible_to< bool >(t<=u), concepts::convertible_to< bool >(u<=t), concepts::convertible_to< bool >(t >=u), concepts::convertible_to< bool >(u >=t))) |