Integers, Floats and Doubles

Lee

Hello,

I'll start with the usual apology for such a basic question, but I can't get my head around this.

Here is my code from the tutorial I am using:

float firstNumber;

float secondNumber;

float floatAnswer;

int integerAnswer;

firstNumber = 10.5F;

secondNumber = 32.5F;

integerAnswer = firstNumber + secondNumber;

MessageBox.Show(integerAnswer.ToString());

This fails because according to the tutorial you cannot store a float variable as an integer. That's fine. What I can't get my head around is the fact that the answer to the sum IS an integer. 10.5 + 32.5 = 43.

43 doesn't have a decimal place so it is an integer, right? What am I missing?

Can anybody simplify this for me, or should I just give up now lol?

Many Thanks

Lee

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
Although floats (and doubles) can store integral values, they are not the same internally as integers because they are stored using a floating point format which is different to the format used by integers.

However, you can convert one type to another using a cast:

integerAnswer = (int)(firstNumber + secondNumber); // works fine

C# is a 'strongly typed' language and the compiler is very fussy about types. Without the cast, it won't allow the conversion because, for all it knows, the result, might be a non-integral number. When you use a cast, it assumes you know what you're doing and rounds to an integer if necessary.

The questions you've asked so far have been sensible ones which show that you're thinking about what you're doing. This is a good thing so don't give up!
Lee15y ago
Thank you very much Vulpes, that makes perfect sense :) Lee
Vulpes15y ago
Yes, you've understood me correctly, Lee :)

The reason why integers are used is that they more efficient (i.e. they produce faster code) than floating point numbers if you only need to work with whole numbers.

Also an int can store numbers with up to 9 (possibly 10) digits whereas a float, whilst having a much larger range, is only accurate up to 7 digits.

On the other hand a double has an even larger range and is accurate to 15 or 16 digits. However, it requires 8 bytes of storage compared to 4 bytes for an int or float.
Lee15y ago
"Without the cast, it won't allow the conversion because, for all it knows, the result, might be a non-integral number. When you use a cast, it assumes you know what you're doing and rounds to an integer if necessary."

Why can't my tutorial have put it like that! If I understand you correctly, what you are saying is that because I have declared the 2 numbers in the sum as Floats, the fact that the answer has no decimal places is irrelevent. It MIGHT have had a decimal place so the code doesn't like it.

That I do understand, thank you.

However this begs another question. You can't store a float value in an integer value, but you CAN store an integer in a float.

Therefore why bother with Int variables? Why not simply declare all number variables as Float or Double? 43.0 will work as a float, so why declare it as an integer? If you're using numbers that may or may not have decimal places, Float is safer. Where is the advantage of using integer?

Many Thanks

Lee