C++ Mortgage payment calculator formula - c++

Question

I've been working on a mortgage calculator for my C++ class. However, I am stuck.
I got the following formula off of Nerdwallet and tried to implement it in my program:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
M=mortgage payment
P=Principal
i=interest
n=number of payments
Here's the code that I am currently using.
#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;
int main(int argc, char** argv)
{
int years, homePrice, creditScore, totalPayments;
float rate, mortgageTotal, monthlyPayment;
cout << "What is the price of the home that you are looking to mortgage?\n";
cin >> homePrice; //Assigns the variable homePrice to a value
cout << "What is your credit score?\n";
cin >> creditScore; //Assigns the creditScore variable a value
cout << "Would you prefer a 15 year or 30 year mortgage? Please type 15 or 30.\n";
cin >> years;
if ( years = 15 ) //If input is 15 year it will go down this logical path
{
if (creditScore >=760) //If their credit rating is equal to or more than 760, their rate will be .043 also nested if.
{
rate = .043;
cout << "Your interest rate is 4.3%\n";
}
else if (creditScore >= 700) //If their credit rating is equal to or more than 700, their rate will be .0455
{
rate = .0455;
cout << "Your interest rate is 4.55%\n";
}
else if (creditScore >= 660) //If their credit rating is equal to or more than 660, their rate will be .048
{
rate = .048;
cout << "Your interest rate is 4.8%\n";
}
else if (creditScore >= 620) //If their credit rating is equal to or more than 620, their rate will be .058
{
rate = .058;
cout << "Your interest rate is 5.8%\n";
}
else if (creditScore >= 580) //If their credit rating is equal to or more than 580, their rate will be .0655
{
rate = .0655;
cout << "Your interest rate is 6.55%\n";
}
else if (creditScore >= 500) //If their credit rating is equal to or more than 500, their rate will be .083
{
rate = .083;
cout << "Your interest rate is 8.3%\n";
}
}
else if ( years=30 )
{
if (creditScore >= 760)
{
rate=.043;
cout <<"Your interest rate is 4.3%\n";
}
else if (creditScore >= 700)
{
rate=.0455;
cout << "Your interest rate is 4.55%\n";
}
else if (creditScore >= 660)
{
rate=.048;
cout << "Your interest rate is 4.8%\n";
}
else if (creditScore >= 620)
{
rate=.058;
cout << "Your interest rate is 5.8%\n";
}
else if (creditScore >= 580)
{
rate=.0655;
cout << "Your interest rate is 6.55%\n";
}
else if (creditScore >= 500)
{
rate=.083;
cout << "Your interest rate is 8.3%\n";
}
}
totalPayments = years * 12;
monthlyPayment = homePrice * [[rate * (1 + rate)pow(totalPayments)] / [(1 + rate)pow(totalPayments) - 1]];
mortgageTotal = monthlyPayment * totalPayments;
cout << "Your mortgage will cost approximately " << mortgageTotal << " and your monthly payment will be " << monthlyPayment << endl;
return 0;
}
However, when I go to compile it, I get the following errors:
Errors
I just don't understand the errors and why they are there.
If someone could help me, I'd greatly appreciate it.
Thank you.

Answer 1

While your math formula uses both []s and ()s for grouping expressions, only ()s can be used in such a way in C++.
pow is a function call, not an in-place operator like you seem to be using it. It needs to look like pow(1 + rate, totalPayments).
Your ifs also are doing assignments (=) instead of comparisons (==). As it is, your code will only follow the first if because it is setting years to 15.

Answer 2

Your mortgage formula seems wrong. Try this
monthlyPayment = homePrice * ((rate * pow(1 + rate, totalPayments)) /
(pow(1.00 + rate, totalPayments) - 1));