iPhone Calculator decimal digits reversed on input - iphone

Question

While doing tutorial work, it took me forever to implement a decimal point, and now i have one, that works in the formula, but the issue is it reverses the input - e.g.. enter 1.4, the calculator screen shows it as 4.1 - i know its something to do with my housekeeping of the variables.. planning to use BOOL's instead of a float..but..any takers?
The code:
- (IBAction) pressedDecimal: (id) sender
{
pressedDec = 1;
}
- (IBAction) pressedDigit: (id) sender
{
if (pressedDec == 1)
{currentNumber = .1 * currentNumber + (double)[sender tag];
calculatorScreen.text = [NSString stringWithFormat:#"%g",currentNumber];
}
else
{
currentNumber = currentNumber * 10 + (double)[sender tag];
calculatorScreen.text = [NSString stringWithFormat:#"%g",currentNumber];
pressedDec = 0;
}
}
- (IBAction) pressedOperation: (id) sender
{
if (currentOperation == 0) result = currentNumber;
else {
switch (currentOperation) {
case 1:
result = result + currentNumber;
break;
case 2:
result = result - currentNumber;
break;
case 3:
result = result * currentNumber;
break;
case 4:
result = result / currentNumber;
break;
case 5:
currentOperation = 0;
break;
}
}
currentNumber = 0;
calculatorScreen.text = [NSString stringWithFormat:#"%g",result];
if ([sender tag] == 0) result = 0;
currentOperation = [sender tag];
}

Answer 1

Consider more carefully what this extract from your code does:
currentNumber = .1 * currentNumber + (double)[sender tag];
(I'm not being very explicit because if I've understood the question right you're doing this in order to learn, and the more you have to think the better you'll learn :-).)

Answer 2

Lesson number 2 here: Stanford iTunes U tutorial covers building a simple calculator. Might be helpful. Either way it's a great tutorial series.