C++基础之std-tuple

类模板std :: tuple是一个固定大小的异构值集合。这是std :: pair的泛化。

http://zh.cppreference.com/w/cpp/utility/tuple

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

std::tuple<double, char, std::string> get_student(int id)
{
    if (id == 0) return std::make_tuple(3.8, 'A', "Lisa Simpson");
    if (id == 1) return std::make_tuple(2.9, 'C', "Milhouse Van Houten");
    throw std::invalid_argument("id");
}

int main()
{
    {
        auto student0 = get_student(0);
        std::cout << "0  ID: 0, " << "GPA: " << std::get<0>(student0) << ", "
            << "grade: " << std::get<1>(student0) << ", " << "name: " << std::get<2>(student0) << '\n';

        double gpa1;
        char grade1;
        std::string name1;
        std::tie(gpa1, grade1, name1) = get_student(1);
        std::cout << "1  ID: 1, " << "GPA: " << gpa1 << ", " << "grade: " << grade1 << ", " << "name: " << name1 << '\n';

        int num = 1;
        auto tup2 = std::forward_as_tuple(num, "hello");//引用，区别于std::make_tuple
        std::get<0>(tup2) = 2;
        std::cout << "2  "<< num << std::endl;
    }
    {
        std::tuple<float, std::string> tup1(static_cast<float>(3.14), "pi");
        std::tuple<int, char> tup2(10, 'a');
        auto tup3 = tuple_cat(tup1, tup2);
        std::cout << "3  " << std::get<0>(tup3) << ", " << std::get<1>(tup3) << ", "
            << std::get<2>(tup3) << ", " << std::get<3>(tup3) << '\n';

        std::tuple_element<0, decltype(tup1)>::type pi = static_cast<float>(3.14);
        std::cout << "4  " << pi << std::endl;

        std::tuple<double, std::string> tup4(3.14, "pi");
        std::cout << "5  " << std::tuple_size<decltype(tup4)>::value;
    }

    getchar();
    return 0;
}

/*
0  ID: 0, GPA: 3.8, grade: A, name: Lisa Simpson
1  ID: 1, GPA: 2.9, grade: C, name: Milhouse Van Houten
2  2
3  3.14, pi, 10, a
4  3.14
5  2
*/

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