# Function

Hi guys: This is a program with one return function name getPayment.

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace test;
double getPayment(int, double, int);
void displayPayment(void);
int main()
{
int carPrice = 0;
int rebate = 0;
double creditRate = 0.0;
double dealerRate = 0.0;
int term = 0;
double creditPayment = 0.0;
double dealerPayment = 0.0;

cout << "Car price (after any trade-in):";
cin >> carPrice;
cout << "Rebate:";
cin >> rebate;
cout << "Credit union rate:";
cin >> creditRate;
cout << "Dealer rate:";
cin >> dealerRate;
cout << "Term in years:";
cin >> term;
displayPayment();
creditPayment = getPayment(carPrice - rebate, creditRate / 12, term * 12);
dealerPayment = getPayment(carPrice, dealerRate / 12, term * 12);
cout << fixed << setprecision(2) << endl;
cout << "Credit union payment: " << creditPayment << endl;
cout << "Dealer payment: \$" << dealerPayment << endl;
system("pause");
return 0;
}

double getPayment(int prin, double monthRate, int months)
{
double monthPay = 0.0;
monthPay = prin * monthRate / (1 - pow(monthRate + 1, -months));
return monthPay;
}

void displayPayment(void)
{
int monthlyPayment = 0;
cout << "Enter monthly payment-->";
cin >> monthlyPayment;
cout << "Monthly Payment-->" << monthlyPayment << endl;
}
----------------------------------------------------------------
I change the getPayment function with void calcPayment(void) function but did mistake in the calculation of creditpayment and dealer payment. Can any one please help me out ? Thanks.

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace test;
void CalcPayment(void);
void displayPayment(void);
int main()
{
CalcPayment();
system("pause");
return 0;
}

void CalcPayment(void)
{
double creditPayment = 0.0;
double dealerPayment = 0.0;
double monthPay = 0.0;
int carPrice = 0;
int rebate = 0;
double creditRate = 0.0;
double dealerRate = 0.0;
int term = 0;
int prin = 0;
double monthRate = 0.0;
int months = 0;
cout << "Car price (after any trade-in):";
cin >> carPrice;
cout << "Rebate:";
cin >> rebate;
cout << "Credit union rate:";
cin >> creditRate;
cout << "Dealer rate:";
cin >> dealerRate;
cout << "Term in years:";
cin >> term;
displayPayment();
//creditPayment = carPrice - rebate, creditRate / 12, term * 12;
//dealerPayment = carPrice, dealerRate / 12, term * 12;
monthRate = creditRate / 12;
months = term * 12;
creditPayment = (carPrice - rebate) * monthRate / (1 - pow(monthRate + 1, -months));
dealerPayment = carPrice * monthRate / (1 - pow(monthRate + 1, -months));
cout << fixed << setprecision(2) << endl;
cout << "Credit union payment: " << creditPayment << endl;
cout << "Dealer payment: \$" << dealerPayment << endl;

}

void displayPayment()
{
int monthlyPayment = 0;
cout << "Enter monthly payment-->";
cin >> monthlyPayment;
cout << "Monthly Payments-->" << monthlyPayment << endl;
}
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Commented:
It looks like you're using creditRate in both calculations, rather than using dealerRate in the dealerPayment calculation. Is that the problem?

Also, if you're not aware, you might want to be careful about your divide by 12, as that's an integer division which will only yield an integer result i.e. 18 / 12 = 1, not 1.5. In order to not have the decimal part truncated, use creditRate / 12.0.
0
Author Commented:
>It looks like you're using creditRate in both calculations, rather than using dealerRate in the dealerPayment calculation. Is that the problem?

Yes I mix it up the calculation.
0
Author Commented:

dealerPayment = carPrice * monthRate / (1 - pow(monthRate + 1, -months));

Thanks.
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Commented:
``````void CalcPayment(void)
{
double creditPayment = 0.0;
double dealerPayment = 0.0;
double monthPay = 0.0;
int carPrice = 0;
int rebate = 0;
double creditRate = 0.0;
double dealerRate = 0.0;
int term = 0;
int prin = 0;
double monthCreditRate = 0.0;
double monthDealerRate = 0.0;
int months = 0;
cout << "Car price (after any trade-in):";
cin >> carPrice;
cout << "Rebate:";
cin >> rebate;
cout << "Credit union rate:";
cin >> creditRate;
cout << "Dealer rate:";
cin >> dealerRate;
cout << "Term in years:";
cin >> term;
displayPayment();
//creditPayment = carPrice - rebate, creditRate / 12, term * 12;
//dealerPayment = carPrice, dealerRate / 12, term * 12;
monthCreditRate = creditRate / 12;
monthDealerRate = dealerRate / 12;
months = term * 12;
creditPayment = (carPrice - rebate) * monthCreditRate / (1 - pow(monthCreditRate + 1, -months));
dealerPayment = carPrice * monthDealerRate / (1 - pow(monthDealerRate + 1, -months));
cout << fixed << setprecision(2) << endl;
cout << "Credit union payment: " << creditPayment << endl;
cout << "Dealer payment: \$" << dealerPayment << endl;

}
``````
And I was a little mistaken what I said about the integer division. creditRate is a double, so the division is not an integer division. It's only an integer division if both operands are integers.
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Author Commented:
Thanks a lot.
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