c++ tuple学习记录(二)

在c++ 中，std::tuple 是一个模板类，位于<tuple>头文件中，用于存储多个不同类型的值。与std::pair类似，但支持存储多个元素，并且每个元素可以是不同的类型。

以下是std::tuple的主要用法

1.创建和初始化std::tuple

#include <tuple>
#include <iostream>
#include <string>


int main()
{
    std:tuple<int,double,std::string> myTuple(42,3.14,"Hello);
    
    auto anotherTuple = std::make_tuple(10,'A',20.5);
    

    std::cout << "Integer: "<< std::get<0>(myTuple)<<" , ";
    std::cout << "Double: "<< std::get<1>(myTuple)<<" , ";
    std::cout << "String: "<< std::get<2>(myTuple)<<"\n";
    return 0;
}

2.访问std::tuple 元素

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, std::string, double> t(1, "Tuple", 3.14);

    // 访问元素
    std::cout << std::get<0>(t) << "\n"; // 输出 1
    std::cout << std::get<1>(t) << "\n"; // 输出 Tuple
    std::cout << std::get<2>(t) << "\n"; // 输出 3.14

    return 0;
}

 

3.结构tuple

c++17引入了结构化绑定，可以方便地结构std::tuple

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, std::string, double> t(1, "Tuple", 3.14);

    // 解构
    auto [x, y, z] = t;

    std::cout << x << " " << y << " " << z << "\n";

    return 0;
}

4.修改tuple 的值

可以使用std::get<N> 修改tuple中的值

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, std::string, double> t(1, "Tuple", 3.14);

    // 修改值
    std::get<0>(t) = 42;
    std::get<1>(t) = "Changed";
    std::get<2>(t) = 6.28;

    std::cout << std::get<0>(t) << " " << std::get<1>(t) << " " << std::get<2>(t) << "\n";

    return 0;
}

5.比较tuple

std::tuple支持比较运算符(==,!=,<,>,<=,>=) ，按字典顺序比较每个元素

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, char> t1(10, 'a');
    std::tuple<int, char> t2(20, 'b');

    if (t1 < t2) {
        std::cout << "t1 is less than t2\n";
    }

    return 0;
}

 

6.获取tuple的元素数量

可以通过std::tuple_size 获取tuple的元素数量

 

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, double, std::string> t(1, 3.14, "Hello");

    std::cout << "Tuple size: " << std::tuple_size<decltype(t)>::value << "\n";

    return 0;
}

 

7.合并tuple

可以使用std::tuple_cat 将多个tuple 合并为一个

#include <tuple>
#include <iostream>

int main() {
    std::tuple<int, char> t1(1, 'a');
    std::tuple<double, std::string> t2(3.14, "Tuple");

    auto merged = std::tuple_cat(t1, t2);

    std::cout << std::get<0>(merged) << " ";
    std::cout << std::get<1>(merged) << " ";
    std::cout << std::get<2>(merged) << " ";
    std::cout << std::get<3>(merged) << "\n";

    return 0;
}

 

8.元组与函数绑定

可以使用std::apply将tuple绑定到函数

#include <tuple>
#include <iostream>


int add(int a, int b)
{
    return a + b;
}

int main()
{

    auto args = std::make_tuple(10,20);

    std::cout << "Sum: "<< std::apply(add,args)<<"\n";
    return 0;
}