http://rosettacode.org/wiki/Ackermann_function

ackermann.cpp

#include <iostream>

unsigned int A(unsigned int m, unsigned int n)
{
  // std::cout << "A(" << m << "," << n << ")" << std::endl;
  
  if(m == 0)
  {
    return n + 1;
  }
  else
  {
    if(n == 0)
	{
	  return A(m - 1, 1);
	}
	else
	{
	  return A(m - 1, A(m, n - 1));
	}
  }
}

int main(int argc, char** argv)
{
  if(argc == 3)
  {
    unsigned int m = atoi(argv[1]);
    unsigned int n = atoi(argv[2]);
	std::cout << A(m, n) << std::endl;
	
	return 0;
  }
  else
  {
    std::cerr << argv[0] << " m n" << std::endl << "where m and n are non-negative integers" << std::endl;
	
	return 1;
  }
}