C++14 variadic function template expect 2 arguments - 0 provided

Question

I'm currently working on a variadic function using template, however, I keep getting the same error:

C2780: 'void print(T,Types...)': expects 2 arguments - 0 provided

even if it is the simplest one:

template <typename T, typename... Types>
void print(T var1, Types... var2)
{
    cout << var1 << endl;

    print(var2...);
}

int main() {
    print(1, 2, 3);
}

the same error again. I wonder what's wrong.

Answer 1

Your calls to print will be like this:

print(1, 2, 3);
print(2, 3);
print(3);
print();

Your template function needs at least one argument (var1), and there is no function that takes zero arguments.

This can easily be solved by adding another function overload to handle the "no argument" case:

void print()
{
    // Do nothing
}

Now this will be called in the

print();

case, and will end the recursion.

---

If C++17 is possible, then fold expressions are available and you could do it with only a single function:

template <typename... Types>
void print(Types&&... var)
{
    ((std::cout << var << "\n"), ...);
}

Answer 2

You need to define two separate overloads, with an empty one for the terminating case:

void print(){
    cout << endl;
}

template <typename T, typename... Types>
void print(T value, Types... args){
    cout << value << " ";
    print(args...);
}