C++11-元组

范型元组

tuple 可以理解为是对老版本pair类模板的扩展，其中的元素个数不再限于两个，而且功能更加丰富

tuple:构造tuple对象所保存的只是构造实参的拷贝

make_tuple:构造tuple对象所保存的只是构造实参的拷贝

tie:通过tie构造的tuple对象，保存构造实参的可写引用

forward_as_tuple:通过forward_as_tuple构造的tuple对象，保存构造实参的原始引用,左值使用左值引用，右值使用右值引用

参见：tuple.cpp

#include <iostream>
#include <tuple>
using namespace std;
int main (void) 
{
    string name   = "张飞";
    int    age    = 25;
    float  height = 1.75;
    // 直接构造tuple对象
    tuple<string, int, float> st1 (name, age, height);
    // 获取tuple元素的值
    cout << get<0> (st1) << endl;
    cout << get<1> (st1) << endl;
    cout << get<2> (st1) << endl;
    // 通过make_tuple构造tuple对象
    auto st2 = make_tuple (name, age, height);
    cout << get<0> (st2) << endl;
    cout << get<1> (st2) << endl;
    cout << get<2> (st2) << endl;
    get<0> (st2) = "赵云";
    get<1> (st2) = 20;
    get<2> (st2) = 1.65;
    cout << get<0> (st2) << endl;
    cout << get<1> (st2) << endl;
    cout << get<2> (st2) << endl;
    cout << name << endl;
    cout << age << endl;
    cout << height << endl;
    // 按以上两种方式构造的tuple对象所保存的只是构造实参的拷贝
    // 通过tie构造tuple对象，保存构造实参的可写引用
    auto st3 = tie (name, age, height);
    cout << get<0> (st3) << endl;
    cout << get<1> (st3) << endl;
    cout << get<2> (st3) << endl;
    get<0> (st3) = "赵云";
    get<1> (st3) = 20;
    get<2> (st3) = 1.65;
    cout << get<0> (st3) << endl;
    cout << get<1> (st3) << endl;
    cout << get<2> (st3) << endl;
    cout << name << endl;
    cout << age << endl;
    cout << height << endl;
    // 通过tie解析tuple对象
    auto st4 = make_tuple ("关羽", 30, 1.85);
    tie (name, age, height) = st4;
    cout << name << endl;
    cout << age << endl;
    cout << height << endl;
    // 通过forward_as_tuple构造tuple对象，保存构造实参的原始引用
    auto st5 = forward_as_tuple (name, age, height);
    cout << &get<0> (st5) << ' ' << &name << endl;
    cout << &get<1> (st5) << ' ' << &age << endl;
    cout << &get<2> (st5) << ' ' << &height << endl;
    get<0> (st5) = "赵云";
    get<1> (st5) = 20;
    get<2> (st5) = 1.65;
    cout << name << endl;
    cout << age << endl;
    cout << height << endl;
    auto st6 = forward_as_tuple ("关羽", 30, 1.85);
    cout << &get<0> (st6) << ' ' << &name << endl;
    cout << &get<1> (st6) << ' ' << &age << endl;
    cout << &get<2> (st6) << ' ' << &height << endl;
    /* 无法对右值引用赋值
    get<0> (st6) = "赵云";
    get<1> (st6) = 20;
    get<2> (st6) = 1.65; */
    return 0;
}