i want the result of an equation rounded to the nearest integer. e.g.
137 * (3/4) = 103
Consider the following incorrect code.
int width1 = 4;
int height1 = 3;
int width2 = 137;
int height2 = width2 * (height1 / width1);
What is the proper way to perform "integer" math in C#?
Do i really have to do:
int height2 = (int)Math.Round(
(float)width2 * ((float)height1 / (float)width1)
);
The elaborate on Jeffery's message, since you generally a better chance of truncated needed decimals than you have of overflowing a 32-bit integer (and because multiplication & division is commutative), you should generally do multiplication before division.
Do multiplication first (as long as they're not likely to overflow) and division second.
3/4 == 0 in integer math (integer math doesn't round on division, it truncates).
If you really need rounding, you have to either work in fixed point, floating point, or play around with the modulus.
As said above, you should do the multiplication before the division. Anyway you could write your expression with casting only the divisor:
int height2 = (int)Math.Round(width2 * (height1 / (float)width1));
int height2 = ((width2 * height1 * 10) + 5) / (width1 * 10);
Prior to any integer division, check to make certain the divisor is not zero. Also note this assumes positive quotient. If negative, roundoff needs to be -5, not +5.
I will fix the incorrect code by adding zero lines of code:
float width1 = 4;
float height1 = 3;
float width2 = 137;
float height2 = width2 * (height1 / width1);
You should use floats for variables that can possibly contain decimals. This includes heights calculated from ratios. You can always cast to int later if that is a problem.
Never cast to float, it has even less precision than a 32-bit integer. If you're going to use floating point, always use double instead of float.