How to get a function to parameter values?

[ctaylor4874]

I can't figure out how to get the double displayFunc(double paymentRate, double balanceWInterest) function to refresh to the new value for balanceWInterest, or balWInt in the main function. Can someone give me some insight on this?

// Cody Taylor



#include <iostream>
#include <cmath>
#include <iomanip>
#include <cctype>

using namespace std;

const string MONTH_PAY = "What will your monthly payment will be?";
const string OPTION_ONE = "1 - 10% of balance with interest";
const string OPTION_TWO = "2 - 20% of balance with interest";
const string OPTION_THREE = "3 - 30% of balance with interest";
const string ANSWER_INPUT1 = "Enter choice from menu above: ";
const string BEG_BAL = "Enter your beginning balance: ";
const string INTEREST = "Enter the credit card's annual interest rate: ";
const double RATE1 = .10;
const double RATE2 = .20;
const double RATE3 = .30;
const int MIN_BALANCE = 100;


int monthPaymentFunc();
double beginningBal(string prompt);
double interestFunc(string promptTwo);
double displayFunc(double paymentRate, double balanceWInterest);
int main()
{
	int userInput;
	double bal;
	double intRate;
	double rateOfPay;
	int numberMonths;
	double balWInt;
	double payment;
	int month;
	double monthsInt;
	double endBal;
	double beginBal;
	
	cout << "This program calculates how long it will take to pay off your credit card balance." << endl << endl;
	
	userInput = monthPaymentFunc() ;
	bal = beginningBal(BEG_BAL) ;
	intRate = interestFunc(INTEREST);
	
	if (userInput == 1)
	{
		rateOfPay = RATE1;
	}
	else
	if (userInput == 2)
	{
		rateOfPay = RATE2;
	}
	else
	if (userInput == 3)
	{
		rateOfPay = RATE3;
	}	
	
	balWInt = (bal * intRate) + bal;
	
	payment = displayFunc( rateOfPay,  balWInt);
	
	month = 0;
	cout << "RESULTS:" << endl;
	cout << "-------------------------------------------------------------------" << endl;
	cout << "      Initial   Month's    Balance     " << rateOfPay << "%   End" << endl;
	cout << "Month  Balance  Interest  w/Interest  Payment  Balance" << endl;
	cout << "-------------------------------------------------------------------" << endl;
	
	month++;
	monthsInt = bal * intRate;
	endBal = balWInt - payment;
	cout << month << setw(10) << bal << setw(10) << monthsInt << setw(10) 
	<< balWInt << setw(10) << payment << setw(10) << endBal << endl;
	
	while(endBal > 0)
	{
		month++;
		monthsInt = endBal * intRate;
		bal = (endBal);
		balWInt = (bal * intRate) + bal;
		endBal = balWInt - payment;
		cout << month << setw(10) << bal << setw(10) << monthsInt << setw(10) 
		<< balWInt << setw(10) << payment << setw(10) << endBal << endl;
	}


 cout << endl << endl;
 system ("PAUSE");
 
 return 0;
}

int monthPaymentFunc()
{
	int userChoice;
	
	cout << MONTH_PAY << endl << setw(40) << OPTION_ONE << endl << setw(40) 
	<< OPTION_TWO << endl << setw(40) << OPTION_THREE << endl << ANSWER_INPUT1;
	
	cin >> userChoice;
	cout << endl;
	
	
	
	while ((userChoice < 1) || (userChoice > 3))
	{
		cout << "Number must be one, two, or three. Try again. ";
		cin >> userChoice;
		cout << endl;
	}
	
	return userChoice;
}

double beginningBal(string prompt)
{
	double begBal;
	cout << prompt;
	cin >> begBal;
	cout << endl;
	
	while(begBal < MIN_BALANCE)
	{
		cout << "Beginning balance must be more than " << MIN_BALANCE << ", try again. ";
		cin >> begBal;
		cout << endl;
		
	}
	
	return begBal;
}

double interestFunc(string promptTwo)
{
	double interestRate;
	double monthlyRate;
	double divisionResult;
	cout << promptTwo;
	cin >> interestRate;
	cout << endl;
	
	while((interestRate < 5) || (interestRate >= 26))
	{
		cout << "Error: Interest rate must be an integer between five, and twenty five." ;
		cout  	<< "Integer may be followed by a decimal.";
		cin >> interestRate;
		cout << endl;
	}
	
	divisionResult = (interestRate / 100);
	monthlyRate = (divisionResult / 12);	
	
	
	return monthlyRate;
}


double displayFunc(double paymentRate, double balanceWInterest)
	{
		double payment;
			
		payment = (balanceWInterest * paymentRate);
		

		return payment;
	}

[keskiverto]

What do you mean by "refresh"? Where/when?

Your displayFunc() performs a calculation. You call it on line 66, i.e. you compute a value and store it into variable "payment" on line 66. If you want to perform the same calculation for different input values later, then you have to call the function again.

[ctaylor4874]

I need the payment value to refresh every time the while loop
while(endBal > 0)
{
month++;
monthsInt = endBal * intRate;
bal = (endBal);
balWInt = (bal * intRate) + bal;
endBal = balWInt - payment;
cout << month << setw(10) << bal << setw(10) << monthsInt << setw(10)
<< balWInt << setw(10) << payment << setw(10) << endBal << endl;
}
runs, so that the payment and the ending balance will both be accurate. Right now it just keeps the same payment value every time the loop runs. I intend on putting this ^^^ in a function once its running correctly, so I wont be able to call the displayFunc(double paymentRate, double balanceWInterest) function in the while loop. Is what I'm saying making any sense?

[keskiverto]

Why do you think that you cannot call a function from a function?