/* power() recursively computes x raised to the power n.
   Receive:  x, a real value, and
             n, an integer
   Return:   x raised to the power n
------------------------------------------------------------*/

double power(double x, int n)
{
  if (n == 0)                      //anchor case
    return 1.0;
  else if (n > 0)                  //inductive step (n > 0)
    return power (x, n - 1) * x;   
  else                             // invalid parameter n
  {
    cerr << "*** power(x,n): n is negative.\n";
    return -1.0;
  }
}