C#: divide an int by 100

How do I divide an int by 100?

eg:

int x = 32894;
int y = 32894 / 100;

Why does this result in y being 328 and not 328.94?

回答1:

When one integer is divided by another, the arithmetic is performed as integer arithmetic.

If you want it to be performed as float, double or decimal arithmetic, you need to cast one of the values appropriately. For example:

decimal y = ((decimal) x) / 100;

Note that I've changed the type of y as well - it doesn't make sense to perform decimal arithmetic but then store the result in an int. The int can't possibly store 328.94.

You only need to force one of the values to the right type, as then the other will be promoted to the same type - there's no operator defined for dividing a decimal by an integer, for example. If you're performing arithmetic using several values, you might want to force all of them to the desired type just for clarity - it would be unfortunate for one operation to be performed using integer arithmetic, and another using double arithmetic, when you'd expected both to be in double.

If you're using literals, you can just use a suffix to indicate the type instead:

decimal a = x / 100m; // Use decimal arithmetic due to the "m"
double b = x / 100.0; // Use double arithmetic due to the ".0"
double c = x / 100d; // Use double arithmetic due to the "d"
double d = x / 100f; // Use float arithmetic due to the "f"

As for whether you should be using decimal, double or float, that depends on what you're trying to do. Read my articles on decimal floating point and binary floating point. Usually double is appropriate if you're dealing with "natural" quantities such as height and weight, where any value will really be an approximation; decimal is appropriate with artificial quantities such as money, which are typically represented exactly as decimal values to start with.

回答2:

328.94 is not an integer. Integer / divide rounds down; that is how it works.

I suggest you cast to decimal: