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 to define a specialization of the template function to stop the recursion at the compile time rather than runtime, just as your struct version did.

template 
int f2()
{
    return N * f2();
}

template <>
int f2<0>()
{
    return 1;
}