% (mod) explanation

Question

Today I was writing a program in C#, and I used % to calculate some index... My program didn't work, so I debugged it and I realized that "%" is not working like in other program languages that I know.

For example:

In Python % returns values like this:

for x in xrange (-5, 6):      print x, "% 5 =", x % 5  -5 % 5 = 0 -4 % 5 = 1 -3 % 5 = 2 -2 % 5 = 3 -1 % 5 = 4 0 % 5 = 0 1 % 5 = 1 2 % 5 = 2 3 % 5 = 3 4 % 5 = 4 5 % 5 = 0 

In C#:

for (int i = -5; i < 6; i++) {     Console.WriteLine(i + " % 5 = " + i % 5); }  -5 % 5 = 0 -4 % 5 = -4 -3 % 5 = -3 -2 % 5 = -2 -1 % 5 = -1 0 % 5 = 0 1 % 5 = 1 2 % 5 = 2 3 % 5 = 3 4 % 5 = 4 5 % 5 = 0 

Did I do something wrong or is % not working like it should?

Answer 1

As explained in the comments, the different behaviour is by design. The different languages just ascribe different meanings to the % operator.

You ask:

How can I use modulus operator in C#?

You can define a modulus operator yourself that behaves the same way as the Python % operator:

int mod(int a, int n) {     int result = a % n;     if ((result<0 && n>0) || (result>0 && n<0)) {         result += n;     }     return result; } 

Answer 2

Both answers are correct. Although personally I think the "always positive" one makes more sense.

You can define your own modulus function that only gives positive answers like this:

int mod(int a, int n) {     return ((a%n)+n) % n; }