fibonacci template C++

fibonacci.cpp

template<int n>
struct fibonacci
{
  static constexpr int value = fibonacci<n-1>::value + fibonacci<n-2>::value;
};
template<>
struct fibonacci<0>
{
  static constexpr int value = 0;
};
template<>
struct fibonacci<1>
{
  static constexpr int value = 1;
};

int main()
{
    fibonacci<40>::value;
    return 0;
}

Using

template <unsigned long long n>
struct fib {
    enum : unsigned long long { result = fib<n - 1>::result + fib<n - 2>::result };
};
template<> struct fib<0> { enum { result = 0 }; };
template<> struct fib<1> { enum { result = 1 }; };

OR

template <unsigned long long n>
struct fib {
    static constexpr unsigned long long result = fib<n - 1>::result + fib<n - 2>::result;
};
template<> struct fib<0> { static constexpr int result = 0; };
template<> struct fib<1> { static constexpr int result = 1; };

you an compute up-to fib<105>::result which is 17704020980446223138.