/* The following code example is taken from the book * "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */template <typename T>class Stack {  private:    std::deque<T> elems;   // elements  public:    void push(T const&);   // push element    void pop();            // pop element    T top() const;         // return top element    bool empty() const {   // return whether the stack is empty        return elems.empty();    }    // assign stack of elements of type T2    template <typename T2>    Stack<T>& operator= (Stack<T2> const&);};