Programming Forums > Application Development > C++

amg11872 · Dec 11th, 2006, 10:39 PM

Hi. I am new to this forum. I have written a program to calculate the outstanding balance, interest payment, and principal payment for a loan. When I compile it does not display any results. I believe the error is in my while loop but I have not had any luck locating the error.

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int main()
{
	float OUTSTANDING_BAL = 80000.000000; 
	const float MONTHLY_PYMT = 300.000000;
	float principal;
	float monInt;
	float balance;
			    	
	cout << "Beginning      Interest        Principal      EndingLoan" << endl;
	cout << "Payment         Payment         Balance         Balance" << endl;
	cout << "_ _ _ _ _      _ _ _ _ _       _ _ _ _ _      _ _ _ _ _ _" << endl;
	
	balance = OUTSTANDING_BAL;

	while (balance <= 80000.000000)
	{
		balance = balance - MONTHLY_PYMT;
		monInt = balance * (0.10/12);

		if (balance < MONTHLY_PYMT)
			principal = balance;
		else
			principal = MONTHLY_PYMT - monInt;

		balance= balance - principal;
					       			
		cout << setiosflags(ios::fixed)
			<< setiosflags(ios::showpoint)
			<< setw(11) << setprecision(6);
	}
	return 0;

I would appreciate any help that I can get.

Jimbo · Dec 11th, 2006, 11:03 PM

So, in your loop, you have the cout with lots of formatting stuff, but you don't actually output anything. I'm guessing that's your problem.

Side note: when copmaring floating point numbers, using < and > is a bit risky, since they aren't stored precisely in memory. It is possible that 80000.0 on some machines may be stored as slightly larger or smaller, which could result in the loop never being run. One way around this is to use a tolerance level, e.g.

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double epsilon = 0.05; // tolerance level
if(balance <= 80000.00 + epsilon)
// or for equality
if(fabs(balance - 80000.00) < epsilon)

PS - Welcome to the forum

amg11872 · Dec 11th, 2006, 11:48 PM

To output the information do I need to include it in the while loop or before.

Jimbo · Dec 12th, 2006, 12:18 AM

You need to cout the data. Like this:

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    cout << setiosflags(ios::fixed)
      << setiosflags(ios::showpoint)
      << setw(11) << setprecision(2);
    cout << MONTHLY_PYMT;
    cout << setw(12) << monInt ; // repeatedly set the width
    cout << setw(13) << principal ; // for each field
    cout << setw(17) << balance << endl; // and a newline at the end

This should be in the loop like it already is. You can play with the widths a bit to get 'em how you want 'em to look. Also, I noticed that once your balance is 0, you'll still loop. You should put another condition to prevent an infinite loop.

amg11872 · Dec 12th, 2006, 6:21 AM

Thanks so much. I made the changes that you suggested and now it is running right.

Dec 11th, 2006, 10:39 PM	#1
amg11872 Newbie Join Date: Dec 2006 Posts: 3 Rep Power: 0	Trouble with while loop. Hi. I am new to this forum. I have written a program to calculate the outstanding balance, interest payment, and principal payment for a loan. When I compile it does not display any results. I believe the error is in my while loop but I have not had any luck locating the error. (Toggle Plain Text) int main() { float OUTSTANDING_BAL = 80000.000000; const float MONTHLY_PYMT = 300.000000; float principal; float monInt; float balance; cout << "Beginning Interest Principal EndingLoan" << endl; cout << "Payment Payment Balance Balance" << endl; cout << "_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _" << endl; balance = OUTSTANDING_BAL; while (balance <= 80000.000000) { balance = balance - MONTHLY_PYMT; monInt = balance * (0.10/12); if (balance < MONTHLY_PYMT) principal = balance; else principal = MONTHLY_PYMT - monInt; balance= balance - principal; cout << setiosflags(ios::fixed) << setiosflags(ios::showpoint) << setw(11) << setprecision(6); } return 0; int main() { float OUTSTANDING_BAL = 80000.000000; const float MONTHLY_PYMT = 300.000000; float principal; float monInt; float balance; cout << "Beginning Interest Principal EndingLoan" << endl; cout << "Payment Payment Balance Balance" << endl; cout << "_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _" << endl; balance = OUTSTANDING_BAL; while (balance <= 80000.000000) { balance = balance - MONTHLY_PYMT; monInt = balance * (0.10/12); if (balance < MONTHLY_PYMT) principal = balance; else principal = MONTHLY_PYMT - monInt; balance= balance - principal; cout << setiosflags(ios::fixed) << setiosflags(ios::showpoint) << setw(11) << setprecision(6); } return 0; I would appreciate any help that I can get.

Dec 11th, 2006, 11:03 PM	#2
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 754 Rep Power: 3	So, in your loop, you have the cout with lots of formatting stuff, but you don't actually output anything. I'm guessing that's your problem. Side note: when copmaring floating point numbers, using < and > is a bit risky, since they aren't stored precisely in memory. It is possible that 80000.0 on some machines may be stored as slightly larger or smaller, which could result in the loop never being run. One way around this is to use a tolerance level, e.g. (Toggle Plain Text) double epsilon = 0.05; // tolerance level if(balance <= 80000.00 + epsilon) // or for equality if(fabs(balance - 80000.00) < epsilon) double epsilon = 0.05; // tolerance level if(balance <= 80000.00 + epsilon) // or for equality if(fabs(balance - 80000.00) < epsilon) PS - Welcome to the forum __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

Dec 12th, 2006, 12:18 AM	#4
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 754 Rep Power: 3	You need to cout the data. Like this: (Toggle Plain Text) cout << setiosflags(ios::fixed) << setiosflags(ios::showpoint) << setw(11) << setprecision(2); cout << MONTHLY_PYMT; cout << setw(12) << monInt ; // repeatedly set the width cout << setw(13) << principal ; // for each field cout << setw(17) << balance << endl; // and a newline at the end cout << setiosflags(ios::fixed) << setiosflags(ios::showpoint) << setw(11) << setprecision(2); cout << MONTHLY_PYMT; cout << setw(12) << monInt ; // repeatedly set the width cout << setw(13) << principal ; // for each field cout << setw(17) << balance << endl; // and a newline at the end This should be in the loop like it already is. You can play with the widths a bit to get 'em how you want 'em to look. Also, I noticed that once your balance is 0, you'll still loop. You should put another condition to prevent an infinite loop. __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

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Dec 11th, 2006, 11:48 PM	#3
amg11872 Newbie Join Date: Dec 2006 Posts: 3 Rep Power: 0	To output the information do I need to include it in the while loop or before.

Dec 12th, 2006, 6:21 AM	#5
amg11872 Newbie Join Date: Dec 2006 Posts: 3 Rep Power: 0	Thanks so much. I made the changes that you suggested and now it is running right.

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Programming Forums > Application Development > C++

Trouble with while loop.