C++元组std::tuple使用详解

#include 
#include 

int main() {
    // 直接构造
    std::tuple t1(42, 3.14, "hello");

    // 使用 make_tuple（自动推导类型）
    auto t2 = std::make_tuple(100, 2.718, "world");

    // 创建空元组
    std::tuple<> empty_tuple;

    return 0;
}

std::tuple person(25, "Alice", 65.5);

int age = std::get<0>(person);        // 25
std::string name = std::get<1>(person); // "Alice"
double weight = std::get<2>(person);   // 65.5

// 修改元素
std::get<0>(person) = 30;

using PersonTuple = std::tuple;

constexpr size_t size = std::tuple_size::value; // 3

using FirstType = std::tuple_element<0, PersonTuple>::type; // int

auto [age, name, weight] = person;

std::cout << age << ", " << name << ", " << weight << "\n";

int a, b;
std::string s;

// 解包到变量
std::tie(a, s, b) = std::make_tuple(10, "test", 3.14);

// 比较元组
auto t1 = std::make_tuple(1, "abc");
auto t2 = std::make_tuple(1, "def");
if (t1 < t2) {
    std::cout << "t1 < t2\n";
}

// 返回多个值
std::tuple find_user(int id) {
    if (id == 42) {
        return std::make_tuple(true, 42, "admin");
    }
    return std::make_tuple(false, -1, "not found");
}

// 使用
auto [found, uid, role] = find_user(42);
if (found) {
    std::cout << "User: " << uid << ", Role: " << role << "\n";
}