Cleaning up and simplifying my code.

[denofthieves]

Hi. This is definitely homework and I feel like I've got most of it down. The code works, but I feel like there's an easier way to do the last bit. I'm not supposed to use global variables.

Is there a way to clean up the last portion? Why can I only get the math to work if I plug in the monPayment calculation after each noMonth declaration?

I'm very new to all of this. I really appreciate any tips or hints.

#include "pch.h"
#include <iostream>
#include <cmath>
#include <iomanip>


using namespace std;

int main()
{
	float price;  // Price of vehicle.
	float tradeIn;  // Trade in price for vehicle.
	float downPayment;  // Down payment.
	float loanAmt;  // Loan amount (calculated).
	float annualIntRate;  // Annual interest rate (fraction).
	float annualIntPercent;  // Annual interest rate (percent).
	float monIntRate;  // Monthly interest rate (fraction).
	int noMonths;  // Number of monthly payments (12, 24, 36, 48 & 60).
	float monPayment; // Monthly payment.
	

	while (true) // While loop for price of vehicle.
	{
		cout << "Enter the price of the vehicle: ";
		cin >> price;
		cout << "You entered $" << fixed << setprecision(2) << price << "." << endl; // Set precision at 2.
		if (price < 50 || price > 50000)  // Validating price.
		{
			cout << "Invalid price. Must be between $50-$50,000." << endl;
			continue;
		}
		else
		{
			break; // End of loop.
		}
	}
	while (true) // While loop for trade in value.
	{
		cout << "Enter the trade in price of your vehicle: ";
		cin >> tradeIn;
		cout << "You entered $" << tradeIn << "." << endl;

		if (tradeIn <= 0 || tradeIn > price)  // Validating trade it price.
		{
			cout << "Invalid trade in price. Must be greater than $0 and less than $"
				<< price << "." << endl;
			continue;
		}
		else
		{
			break;  // End of loop.
		}
	}
	while (true) // While loop for down payment.
	{
		cout << "Enter the down payment for the vehicle: ";
		cin >> downPayment;
		cout << "You entered $" << downPayment << "." << endl;

		if (downPayment < 0 || downPayment > price - tradeIn)  // Validating down payment.
		{
			cout << "Invalid down payment. Your down payment should be less than $"
				<< price - tradeIn << "." << endl;
			continue;
		}
		else
		{
			break;  // End of loop.
		}
	}
	while (true) // While loop for annual interest rate.
	{
		cout << "Enter the annual interest rate of the vehicle as a decimal: ";
			cin >> annualIntRate;
			annualIntPercent = annualIntRate * 100.0;  // Calculate annual interest rate as a percent.
			cout << "You entered " << annualIntPercent << "%." << endl; // Convert to %.

			if (annualIntRate < 0 || annualIntRate > .50)  // Validating annual interest rate.
			{
				cout << "Invalid annual interest rate. Your rate should be between 0 and .50." << endl;
				continue;
			}
			else
			{
				break;  // End of loop.
			}
	}

	monIntRate = annualIntRate / 12.0;  // Calculate monthly interest rate.
	loanAmt = price - downPayment - tradeIn;  // Calculate loan amount.

	cout << "\n Some Guy's Used Cars:" << "\n" << endl;  // Title for table.

	cout << setw(25) << "Vehicle Price" << setw(15) << "$" << price << endl;  // Price.
	cout << setw(25) << "Trade In Value" << setw(15) << "$" << tradeIn << endl;  // Trade in value.
	cout << setw(25) << "Down Payment" << setw(15) << "$" << downPayment << endl; // Down payment.
	cout << setw(48) << "----------" << endl;
	cout << setw(25) << "Loan Amount" << setw(15) << "$" << loanAmt << "\n" << endl;  // Loan amount.

	cout << setw(25) << "Annual interest rate" << setw(20) << annualIntPercent << "% \n" << endl;  // Annual interest rate.

	cout << "Monthly Payment Options: \n" << endl;  // Title for table.
	noMonths = 12;
	monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));  // Payment for 12 months.
	cout << setw(25) << "12 Months" << setw(15) << "$" << monPayment << endl;
	noMonths = 24;
	monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));  // Payment for 24 months.
	cout << setw(25) << "24 Months" << setw(15) << "$" << monPayment << endl;
	noMonths = 36;
	monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));  // Payment for 36 months.
	cout << setw(25) << "36 Months" << setw(15) << "$" << monPayment << endl;
	noMonths = 48;
	monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));  // Payment for 48 months.
	cout << setw(25) << "48 Months" << setw(15) << "$" << monPayment << endl;
	noMonths = 60;
	monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));  // Payment for 60 months.
	cout << setw(25) << "60 Months" << setw(15) << "$" << monPayment << endl;

	return 0;
}

[tpb]

    cout << "Monthly Payment Options: \n\n"
    for (int noMonths = 12; noMonths <= 60; noMonths += 12) {
        double monPayment = (loanAmt * monIntRate) / (1.0 - pow(1 + monIntRate, -noMonths));
        cout << setw(18) << noMonths << " Months" << setw(15) << "$" << monPayment << '\n';
    }

I don't know if I got the spacing right.

You can simplify your input loops a little, too.

    // you just need to do this once.
    cout << fixed << setprecision(2);

    while (true) {
        cout << "Enter the price of the vehicle: ";
        cin >> price;
        cout << "You entered $" << price << ".\n";  // <-- this is kind of pointless (they can already see what they just entered)
        if (price >= 50 && price <= 50000)
            break;
        cout << "Invalid price. Must be between $50-$50,000.\n";
    }

[denofthieves]

Thank you, this was incredibly helpful. I knew I'd learned the concept but I couldn't figure out how to implement it.