operator==

template<class T>
    valarray<bool> operator==(const valarray<T>& x,
        const valarray<T>& y);
template<class T>
    valarray<bool> operator==(const valarray<T> x, const T& y);
template<class T>
    valarray<bool> operator==(const T& x  const valarray<T>& y);

The first template operator returns an object of class valarray<bool>, 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].