Thread: Arithmetic overflows

Hi again, simple question:
If I have some calculation like:

Code:

int val = (int)exp*3600000/(uint)time

And say exp is 4000, time is nearly 3600000, will the calculation cause an overflow because it calculates 4000*3600000 = 14400000000 first? Or is this compiler specific, or can I control it via:

Code:

val = exp*(3600000/time)

Thanks in advance.

I'd guess that the first is compiler specific, and I'd do the second one first, yeah.. Parenthesis precedence should keep it from overflowing.

Yeah, i'd divide first as long as you are in no risk of losing precision. Your second example makes no difference however as divide has precedence over multiplication. Alternatively you could always use a larger datatype, say Uint64. Or you could test for an overflow.

Really, I thought it worked using BODMAS?

Edit: Yeah, you are right. So what would evaluate first? would it be left to right?

Thanks for you answers.

As exp and time tend to vary between minus several million and plus several million, I choose to use float variables instead of integers. Grants me an extra bonus to precision too. I multiply first now by the way.