C programming question help please? [closed]

Question

What does the expression S+=i*(2*(i%2)-1) mean while writing a code in C?

I know that % 2 mean dividing something and the remainder is our answer but how about the whole thing?

moeryn · Accepted Answer · 2013-04-24 07:15:54Z

Lets assume the code is something like this :

double S;
for(int i ; i < BIG_NUMBER ; ++i){
  S+=i*(2*(i%2)-1);
}

S is call an accumulator, because each step you will take the last value and add to that the result of i*(2*(i%2)-1).

The i*(2*(i%2)-1) is pretty simple :

So basically if the number is even you add -i, if the number is not even you add i to S.

Here what S looks like

closed as off topic by tdammers, thorsten müller, Blrfl, Giorgio, Kilian Foth Apr 24 at 11:37