/**
  * payment.cpp
  * Anthony Larrain
  * Spring 2006, csc309
  *
  * This program will compute the monthly payment on a loan, given the 
  * loan amount, rate in years and number of years of the loan
  */
#include <cmath>    // needed for the pow function
#include <iostream>
#include <iomanip>

using namespace std;

void getInput(double& principal, double& rate, int& years);
double computePayment(double principal, double rate, int years);
void showPayment(double principal,double rate, int years);

const int MONTHS_IN_YEAR = 12;
const int PERCENT_TO_DECIMAL = 100;

int main(int argc, char *argv[])
{
    double principal,rate;
    int years;
    getInput(principal,rate, years);
    showPayment(principal,rate, years);   
    system("PAUSE");
    return EXIT_SUCCESS;
}
void getInput(double& principal,double& rate, int& years){
     cout <<"Enter the amount you would like to borrow" << endl;
     cin >> principal;
     cout <<"Enter the rate of the loan" << endl;
     cin >> rate;
     cout <<"Enter the number of years" << endl;
     cin >> years;
     return;
}
double computePayment(double principal, double rate, int years){
       double monthlyRate =  rate / PERCENT_TO_DECIMAL / MONTHS_IN_YEAR;
       double numerator = monthlyRate * pow(monthlyRate + 1, MONTHS_IN_YEAR * years);
       double denominator = pow(monthlyRate + 1, MONTHS_IN_YEAR * years) - 1;
       return principal * numerator / denominator;
}
void showPayment(double principal,double rate, int years){
     cout <<"Your monthly payment is " << fixed << setprecision(2) 
          <<"$" << computePayment(principal,rate,years) << endl;
}