如何使用初始化列表初始化std::variant？

std::variant<int, double, std::string> v;

#include <iostream>
#include <variant>
#include <string>

int main() {
    // 使用初始化列表初始化 std::variant
    std::variant<int, double, std::string> v = 42;

    // 访问 variant 中的值
    if (std::holds_alternative<int>(v)) {
        std::cout << "Variant holds an int: " << std::get<int>(v) << std::endl;
    } else if (std::holds_alternative<double>(v)) {
        std::cout << "Variant holds a double: " << std::get<double>(v) << std::endl;
    } else if (std::holds_alternative<std::string>(v)) {
        std::cout << "Variant holds a string: " << std::get<std::string>(v) << std::endl;
    }

    return 0;
}

if (std::holds_alternative<int>(v)) {
    std::cout << "Variant holds an int: " << std::get<int>(v) << std::endl;
} else {
    std::cout << "Variant does not hold an int." << std::endl;
}