Recursion Primer using C++: Part 3

// Compile time Generative Nested Recursion

#include <iostream>

template <int m, int n> 
struct Ackermann 
{ 
	// nested recursive call 
	enum { value = Ackermann<m-1, Ackermann<m, n-1>::value>::value }; 
}; 

template <int m> struct Ackermann<m, 0> 
{ 
	// linear recursive call 
	enum { value = Ackermann<m-1, 1>::value }; 
}; 

// termination condition 
template <int n> 
struct Ackermann<0, n> 
{ 
	enum { value = n + 1 }; 
};

int main()
{
	std::cout << Ackermann<2, 3>::value << std::endl; 
}