/* Faan Tone Liu
   Jan 28, 2003
   Demo program for cmp 1672
   Shows a recursive function: calculate integer powers
 */

#include <iostream>
using namespace std;

// prototype for our recursive function that calculates integer powers
int integer_power(int b, int e);

int main()
{
    int base(-1), exponent(-1);
    cout << "This program calculates integer powers." << endl;
    cout << "Input the base and exponent: "; 
    cin >> base >> exponent;
    while (exponent < 0) {
        cout << "The exponent must be non-negative.";
        cout << "Input the base and exponent: "; 
        cin >> base  >> exponent;
    }
    cout << base << " to the " << exponent << " power = " <<
         integer_power(base, exponent) << endl;
    return 0;
}

// recursive function to calculate integer powers  - returns b^e 
// base case:  When the exponent is 0 or 1, then the answer is easy, just
// return it.  When exponent==0, the answer is 1, when exponent==1, the
// answer is just the base.
// recursive step:  b^e = b*b^(e-1)
int integer_power(int b, int e)
{
    if (e == 0) return 1;
    if (e == 1) return b;
    return b*integer_power(b, e-1);
}