// Ex5_15.cpp (based on Ex5_01.cpp)
// A recursive version of x to the power n
#include <iostream>
using std::cout;
using std::endl;
        
double power(double x, int n);         // Function prototype
        
int main()
{
  double x { 2.0 };                    // Different x from that in function power
  double result {};

  // Calculate x raised to powers -3 to +3 inclusive
  for (int index { -3 }; index <= 3; index++)
    cout << x << " to the power " << index << " is " << power(x, index)<< endl;
        
  return 0;
}
        
// Recursive function to compute integral powers of a double value
// First argument is value, second argument is power index
double power(double x, int n)
{
   if(n < 0)
   {
      x = 1.0/x;
      n = -n;
   }
   if(n > 0)
      return x*power(x, n-1);
   else
      return 1.0;
}