c++ - How I declare a std::tuple using variadic templates?

Question

Perhaps I being naive here, but I believe the following code should compile:

template <typename ... T>
struct Test {
        std::tuple<T> foo;
};

int main() {
        struct Test<int, long> test;

        return 0;
}

Instead g++ complains:

test.cpp:5: error: parameter packs not expanded with '...':
test.cpp:5: note:         'T'

What am I missing?

Answer 1

You do that by expanding the pack with ...:

template <typename... T>
struct Test
{
    std::tuple<T...> foo;
    //         ^^^^
};