Floating Point Math

Question

Hi,
I have following code:
float totalSpent;
int intBudget;
float moneyLeft;
totalSpent += Amount;
moneyLeft = intBudget - totalSpent;
And this is how it looks in debugger: http://www.braginski.com/math.tiff
Why would moneyLeft calculated by the code above is .02 different compared to the expression calculated by the debugger?
Expression windows is correct, yet code above produces wrong by .02 result. It only happens for number very large numbers (yet way below int limit)
thanks

Answer 1

Thank you all for help!
Could someone please point me out why first variable printed incorrect, while second is correct:
NSDecimalNumber *intBalance;
NSDecimalNumber *Amount;
NSDecimalNumber *leftAmount;
NSNumberFormatter *currencyStyle;
NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain
scale:2 raiseOnExactness:NO raiseOnOverflow:NO
raiseOnUnderflow:NO raiseOnDivideByZero:NO];
currencyStyle = [[NSNumberFormatter alloc] init];
[currencyStyle setFormatterBehavior:NSNumberFormatterBehavior10_4];
[currencyStyle setNumberStyle:NSNumberFormatterCurrencyStyle];
intBalance = [NSDecimalNumber decimalNumberWithString:@"999999"];
Amount = [NSDecimalNumber decimalNumberWithString:@"99999.59"];
leftAmount = [intBalance decimalNumberBySubtracting: Amount withBehavior: handler];
NSLog(@"Number is: %.2f, %@", [leftAmount floatValue], [currencyStyle stringFromNumber:leftAmount]);
Number is: 899999.44, $899,999.41
Message was edited by: leonbrag