// Ex5_01.cpp
  // Declaring, defining, and using a function
  include <iostream>
  using std::cout;
  using std::endl;
  
  double power(double x, int n);    // Function prototype
  
  int main(void)
  {
     int index = 3;                 // Raise to this power
     double x = 3.0;                // Different x from that in function power
     double y = 0.0;
  
     y = power(5.0, 3);             // Passing constants as arguments
     cout << endl
          << "5.0 cubed = " << y;
  
     cout << endl
          << "3.0 cubed = " 
          << power(3.0, index);     // Outputting return value
  
     x = power(x, power(2.0, 2.0)); // Using a function as an argument
     cout << endl                   // with auto conversion of 2nd parameter
          << "x = " << x;
  
     cout << endl;
     return 0;
  }
  
  // Function to compute positive integral powers of a double value
  // First argument is value, second argument is power index
  double power(double x, int n)
  {                                 // Function body starts here...
     double result = 1.0;           // Result stored here
     for(int i = 1; i <= n; i++)
        result *= x;
     return result;
  }