C++ 2.0

zishen

今天学侯捷老师的C++课程，Variadic Templates

像这样规格输出，我想尝试把tuple改成vector，但是不知道为什么只能输出前两个数？
请大佬解惑！！！

Hamon

[C++] 纯文本查看 复制代码

#include <iostream>
#include <vector>
using namespace std;
template<int IDX, int MAX, typename...Args> 

struct PRINT_TUPLE {

    static void print(ostream& os, const vector<Args...>& t) { 
        
        os<< t[IDX]<<(IDX+1== MAX ?"":",");

        PRINT_TUPLE<IDX + 1, MAX, Args...>::print(os,t);
    }
};

template <int MAX,typename... Args> 

struct PRINT_TUPLE<MAX, MAX,Args...>{

    static void print(ostream& os, const vector<Args...>& t) {} 
};

template <typename... Args>

ostream& operator<<(ostream& os, const vector<Args...>& t){
    os<<"t.size :"<<t.size() <<'\n';
    os<<"sizeof :"<<sizeof...(Args) <<'\n';
    os<<"[";
    PRINT_TUPLE<0, sizeof...(Args), Args...>::print(os,t); 
    return os <<"]";
}

int main()
{
    vector<int> arr{1,2,3,4};
    cout<<arr;

}

输出：
t.size :4
sizeof :2
[1,2]

ciker_li

不太懂...

AhKeiya

[C++] 纯文本查看 复制代码

#include <iostream>
#include <vector>
using namespace std;

template <int IDX, int MAX, typename... Args>
struct PRINT_TUPLE {
    static void print(ostream& os, const vector<Args...>& t) {
        os << t[IDX];
        if (IDX + 1 < MAX) {
            os << ",";
            PRINT_TUPLE<IDX + 1, MAX, Args...>::print(os, t);
        }
    }
};

template <int MAX, typename... Args>
struct PRINT_TUPLE<MAX, MAX, Args...> {
    static void print(ostream& os, const vector<Args...>& t) {}
};

template <typename... Args>
ostream& operator<<(ostream& os, const vector<Args...>& t) {
    os << "t.size: " << t.size() << '\n';
    os << "sizeof: " << min(2, t.size()) << '\n';  // Use min(2, t.size()) instead of sizeof...(Args)
    os << "[";
    PRINT_TUPLE<0, min(2, t.size()), Args...>::print(os, t);
    return os << "]";
}

int main() {
    vector<int> arr{1, 2, 3, 4};
    cout << arr;
}

zishen

AhKeiya 发表于 2024-1-21 21:44
[mw_shl_code=cpp,true]#include
#include
using namespace std;

报错： “min”: 未找到匹配的重载函数