C++标准库 -- tuple

头文件：<tuple>

可访问属性：

无（用get方法来访问数据）

可访问方法：

其他相关方法：

例子：

　　例子1：构造tuple

    tuple<int, float, string> t0;
    tuple<int, float, string> t1(1, 2.0, "three");
    auto t2 = make_tuple(2, 2, "asdf", 3.2);
    tuple<int, string> t3(make_pair(1, "kaima")); //use pair to init tuple
    auto t4 = t1;
    tuple<int, string> t5 = make_pair(1, "John");
　　

　　例子2：访问数据

    tuple<int, float, string> t1(1, 2.0, "three");
    cout << get<0>(t1) << " : " << get<1>(t1) << " : " << get<2>(t1) << endl;

　　例子3：关系比较

    tuple<int, float, string> t1(1, 2.0, "three");
    tuple<int, float, string> t2(1, 1.0, "kaima");

    if(t1 > t2) // >= < <= == !=
        cout << "t1 > t2" << endl;

　　例子4：交换值

    swap(t1, t2);
    t1.swap(t2);

　　例子5：reference构成的tuple

    string s = "Hello";
    tuple<string&> t1(s);
    get<0>(t1) = "t1";
    cout << s << endl; //t1

    auto t2 = make_tuple(ref(s));
    get<0>(t2) = "t2";
    cout << s << endl; //t2

    auto t3 = tie(s);
    get<0>(t3) = "t3";
    cout << s << endl; //t3

其他：

（1）“接受不定个数的实参”的构造函数被声明为explicit。

（2）元素个数：tuple_size<tupleType>::value

（3）第idx个元素的类型：tuple_element<idx, tupleType>::type

（4）连接tuple：tuple_cat(t1, t2..)

额外：

使用以下代码可以直接cout一个tuple。

template <int IDX, int MAX, typename... Args>
struct PRINT_TUPLE {
    static void print(ostream& strm, const tuple<Args...>& t) {
        strm << get<IDX>(t) << (IDX+1==MAX ? "" : ",");
        PRINT_TUPLE<IDX+1, MAX, Args...>::print(strm, t); //recursion
    }
};

//end the recursion
template <int MAX, typename... Args>
struct PRINT_TUPLE<MAX, MAX, Args...> {
    static void print(ostream& strm, const tuple<Args...>& t) {
        //null
    }
};

template <typename... Args>
std::ostream& operator << (ostream& strm, const tuple<Args...>& t) {
    strm << "[";
        PRINT_TUPLE<0, sizeof...(Args), Args...>::print(strm, t);
        return strm << "]";
}