inline FLEX_ALWAYS_INLINE_FLATTEN flex_float operator()(flex_date_time dt) const { return dt.microsecond_res_timestamp(); }
inline FLEX_ALWAYS_INLINE_FLATTEN bool operator()(const flex_float t, const flex_date_time u) const { return t < u.microsecond_res_timestamp(); }
inline FLEX_ALWAYS_INLINE_FLATTEN bool operator()(const flex_float t, const flex_date_time u) const { return std::fabs(t - u.microsecond_res_timestamp()) < flex_date_time::MICROSECOND_EPSILON; }