operator+

template<class T>
    valarray<T> operator+(const valarray<T>& lhs,
        const valarray<T>& rhs);
template<class T>
    valarray<T> operator+(const valarray<T> lhs, const T& rhs);
template<class T>
    valarray<T> operator+(const T& lhs, const valarray<T>& rhs);

The first template operator returns an object of class valarray<T>, each of whose elements I is x[I] + y[I]. The second template operator stores in element I x[I] + y. The third template operator stores in element I x + y[I].