Why won't this program compile?

Question

C++ / C#

template <typename bang, class bing> bang func(bang a, bing b)
{
    return a + b;
}
void func(double a, int b) {
    a + b;
}
int main()
{
    int b = 5;
    double a = 15.5;
    cout << func(a, b);
    return 0;

Answer 1

void

Answer 2

Try compiling and look for errors. And if you are in an exam / interview, then you should do it :)