complex<T>& operator+=(const T& rhs);
complex<T>& operator-=(const T& rhs);
complex<T>& operator*=(const T& rhs);
complex<T>& operator/=(const T& rhs);
template<class X> complex<T>& operator+=(const complex<X>& rhs);
template<class X> complex<T>& operator-=(const complex<X>& rhs);
template<class X> complex<T>& operator*=(const complex<X>& rhs);
template<class X> complex<T>& operator/=(const complex<X>& rhs);