模板的模板参数使用示例

注意：函数模板不支持模板的模板参数。

Stack7.h中定义的Stack：

#ifndef STACK7_H
#define STACK7_H

#include <deque>
#include <stdexcept>
#include <memory>

template <typename T,
        template <typename ELEM, typename = std::allocator<ELEM> >
        class CONT = std::deque>
class Stack
{
public:
    void push(T const&);
    void pop();
    T top() const;
    bool empty() const
    {
        return elems.empty();
    }

    template<typename T2,
            template<typename ELEM2, typename = std::allocator<ELEM2> >
            class CONT2>
    Stack<T, CONT>& operator = (Stack<T2, CONT2> const&);
private:
    CONT<T> elems;
};

template <typename T, template <typename, typename> class CONT>
void Stack<T, CONT>::push(T const& elem)
{
    elems.push_back(elem);
}

template <typename T, template <typename, typename> class CONT>
void Stack<T, CONT>::pop()
{
    if (elems.empty())
        throw std::out_of_range("Stack<>::pop(): empty stack");

    elems.pop_back();
}

template <typename T, template <typename, typename> class CONT>
T Stack<T, CONT>::top() const
{
    if (elems.empty())
        throw std::out_of_range("Stack<>::top(): empty stack");

    return elems.back();
}

template <typename T, template <typename, typename> class CONT>
template <typename T2, template <typename, typename> class CONT2>
Stack<T, CONT>& Stack<T, CONT>::operator = (Stack<T2, CONT2> const& op2)
{
    if ((void*)this == (void*)&op2)
        return *this;

    Stack<T2, CONT2> tmp(op2);
    elems.clear();
    while (!tmp.empty())
    {
        elems.push_front(tmp.top());
        tmp.pop();
    }

    return *this;
}

#endif // STACK7_H

测试代码main.cpp:

#include <iostream>
#include <string>
#include <cstdlib>
#include <vector>
#include "Stack7.h"

using namespace std;

int main()
{
    try
    {
        Stack<int, std::vector> vecStack;
        vecStack.push(2);
        vecStack.push(3);
        std::cout << "vector Stack‘s top: " << vecStack.top() << std::endl;
        vecStack.pop();

        Stack<int> intStack;
        Stack<float> floatStack;

        intStack.push(6);
        intStack.push(7);

        floatStack.push(9.9);

        floatStack = intStack;

        std::cout << floatStack.top() << std::endl;
        floatStack.pop();
        std::cout << "float Stack‘s top:" << floatStack.top() << std::endl;
        floatStack.pop();
        std::cout << "float Stack‘s top:" << floatStack.top() << std::endl;
        floatStack.pop();
    }
    catch (std::exception const& ex)
    {
        std::cerr << "Exception: " << ex.what() <<std::endl;
    }

    return 0;
}

结果：