<stack>

namespace std {
template<class T, class Cont>
    class stack;
//    TEMPLATE FUNCTIONS
template<class T, class Cont>
    bool operator==(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
template<class T, class Cont>
    bool operator!=(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
template<class T, class Cont>
    bool operator<(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
template<class T, class Cont>
    bool operator>(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
template<class T, class Cont>
    bool operator<=(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
template<class T, class Cont>
    bool operator>=(const stack<T, Cont>& lhs,
        const stack<T, Cont>&);
    };

Include the STL standard header <stack> to define the template class stack and two supporting templates.