Math.Pow（10，Math.Abs​​（1））等于10吗？

Question

I'm currently maintaining a code of a former colleague, and found following code (example):

double someValue = 20, someResult;

someResult = (Convert.ToInt32(Math.Round(someValue / (Math.Pow(10, Math.Abs(1))), MidpointRounding.AwayFromZero) * Math.Pow(10, Math.Abs(1))) + 10) - someValue;

and i wonder, why he used Math.Pow(10, Math.Abs(1)) instead of 10 ? Is it because of inaccuracy or some sort of?

The result is the same, if the code is changed to:

someResult = (Math.Round(someValue / 10, MidpointRounding.AwayFromZero) * 10 + 10) - someValue;

Answer 1

The only difference between using 10 instead of (Math.Pow(10, Math.Abs(1)) will be the type. If you write 10 in code the compiler will treat the number as an int . Math.Pow however will return a double .

Sometimes this could make a difference. For example if someValue was an int then someValue/10 would be using integer division and thus might not do what you expect. In this case though someValue is a double so you will use floating point division either way.

So yes, you are safe here replacing the Math.Pow call with just 10 .

As for why it is like this - most often I find this sort of code exists because it was originally more complicated and then got simplified. eg it might have originally been something like Math.Pow(10,precision) or something like that which needed the method call. Then somebody decided to always make precision 1 and updated accordingly without actually simplifying any code such as this that could be simplified.

The actual why is pure speculation though. If this is in source control there might be a commit comment that explains it or if not it might allow you to find the author and ask them...