C++第09课 模板 （二）

1.可变参模板函数

//列表方式展开
template<class _Ty>
void print(_Ty data)
{
    cout << data << endl;
}
template<class ...Args>
void printData(Args... args)
{
    int array[] = { (print(args),0)... };
}
//递归方式展开
void printData2()
{
    cout << endl;
}

template<class _Ty,class ...Args>
void printData2(_Ty data, Args ...args)
{
    cout << data << "\t";
    printData2(args...);
}

//求任意个整数的和
//1.递归展开
int sum()
{
    return 0;
}
template<class _Ty,class ...Args>
int sum(_Ty data, Args ...args)
{
    return data + sum(args...);
}
//2.列表展开
template<class _Ty>
_Ty sum2(_Ty data)
{
    return data;
}
template<class ...Args>
int sum1(Args... args)
{
    int array[] = { (0,sum2(args))... };
    int sum = 0;
    for (int i : array)
    {
        sum += i;
    }
    return sum;
}

int main()
{
    printData(1, "love", 2.2f, 'A');
    printData2(1, "love", 2.2f, 'A');
    cout << sum(1, 2, 3, 4, 5) << endl;
    cout << sum1(1, 2, 3, 4, 5) << endl;
    return 0;
}

 

2.可变参数模板类

//模板特化+递归的方式展开参数包
template <class ...Args> 
class Tup;
//特化
template <>
class Tup<> {};
//递归方式实现
template <class _Ty,class ...Args>
class Tup<_Ty, Args...> 
{
public:
    Tup(_Ty data, Args ...args) :data(data), args(args...) {}
    _Ty& head() 
    {
        return data;
    }
    Tup<Args...>& next() 
    {
        return args;
    }
protected:
    _Ty data;
    Tup<Args...> args;
};
void testTup() 
{
    Tup<int, string, char> tup(1, "string", 'A');
    cout << "第一个参数：" << tup.head() << " 第二个参数:" << tup.next().head()
        << " 第三个参数:" << tup.next().next().head() << endl;
    Tup<string,int,int,int,int> mm("mm",18,98,88,88);
}

//模板特化+继承的方式展开参数包
template <class ...Args>
class Test;

template <>
class Test<> 
{
};
/*
template <class _This, class... _Rest>
class tuple<_This, _Rest...> : private tuple<_Rest...>
*/
template <class _Ty,class ...Args>
class Test<_Ty, Args...> :public Test<Args...>
{
public:
    Test(_Ty data, Args... args) :data(data), Test<Args...>(args...) {}
    _Ty& head() 
    {
        return data;
    }
    Test<Args...>& next() 
    {
        return *this;
    }
protected:
    _Ty data;
};
void testTest() 
{
    Test<int, string, char> test(1, "string", 'A');
    cout << "第一个参数：" << test.head() << " 第二个参数:" << test.next().head()
        << " 第三个参数:" << test.next().next().head() << endl;
    Test<string, int, int, int, int> mm("mm", 18, 98, 88, 88);
}
int main() 
{
    testTup();
    testTest();
    tuple<int, string, char> testTuple;
    return 0;
}