constexpr duration operator+() const;
Returns: *this.
constexpr duration operator-() const;
Returns: duration(-rep_).
constexpr duration& operator++();
Effects: As if by ++rep_.
Returns: *this.
constexpr duration operator++(int);
Returns: duration(rep_++).
constexpr duration& operator--();
Effects: As if by --rep_.
Returns: *this.
constexpr duration operator--(int);
Returns: duration(rep_--).
constexpr duration& operator+=(const duration& d);
Effects: As if by: rep_ += d.count();
Returns: *this.
constexpr duration& operator-=(const duration& d);
Effects: As if by: rep_ -= d.count();
Returns: *this.
constexpr duration& operator*=(const rep& rhs);
Effects: As if by: rep_ *= rhs;
Returns: *this.
constexpr duration& operator/=(const rep& rhs);
Effects: As if by: rep_ /= rhs;
Returns: *this.
constexpr duration& operator%=(const rep& rhs);
Effects: As if by: rep_ %= rhs;
Returns: *this.
constexpr duration& operator%=(const duration& rhs);
Effects: As if by: rep_ %= rhs.count();
Returns: *this.