recursive template instantiation exceeded maximum depth of 256

Question

I was trying to rewrite the Factorial implementation using constexpr function but for some reason I have no idea why I get a compile error:

Answer 1

You need a stopping state like the following:

template <>
int f2<0>()
{
   return 0;
}

since f2() has to be instantiated, you have your stopping state in your other case here:

template <> struct Factorial<0>

But if you are using constexpr you don't really need to use templates at all since the whole point is that it will be done at compile time, so turn it into this:

constexpr int f2(int n)
{
  return n == 0 ? 1 : (n * f2(n-1));
}