Inverse Modulo?

Questions & Answers
1

if (Input.GetKeyDown(“q”))
{
int i = 0;
while (!Players*.GetComponent().Active && (i < Players.Count))*
{ i++; }
Players*.GetComponent().Active = false;*
Players*.GetComponent().OneTime = false;*
//if active
Players[(i + 1) % Players.Count].GetComponent().Active = true;
Players[(i + 1) % Players.Count].GetComponent().OneTime = false;
}
in this Script it turns off Active for the current active object and turns it on for the next one in the list.
if (Input.GetKeyDown(“e”))
{
int i = 0;
while (!Players*.GetComponent().Active && (i < Players.Count))*
{ i++; }
Players*.GetComponent().Active = false;*
Players*.GetComponent().OneTime = false;*
//if active
Players[(i - 1) % Players.Count].GetComponent().Active = true;
Players[(i - 1) % Players.Count].GetComponent().OneTime = false;
}
this script should do the same but in the inverted direction but the modulo does not work with - numbers. so i made this script:
if (Input.GetKeyDown(“e”))
{
int i = 0;
while (!Players*.GetComponent().Active && (i < Players.Count))*
{ i++; }
Players*.GetComponent().Active = false;*
Players*.GetComponent().OneTime = false;*
//if inactive
i–;
if (i < 0){i = Players.Count;}
Players*.GetComponent().Active = true;*
Players*.GetComponent().OneTime = false;*
}
but for some reason this still does not work… can someone tell me where the mistake is?

2

Your issue is that the modulo operator will keep the sign of the number you’re dividing, This is explained in the documentation. So if you have a value smaller than 0 (namely “-1” the modulo operator will return “-1” and not the divisor-1).

Your last code does actually work, however the value you set inside your if statement is wrong. The highest valid index is Player.Count - 1.

ps: Now I maybe understand what you meant by your comment above, however it’s misleading the way it’s worded. The modulo operator doesn’t work for negative numbers since it will return just the negative modulo. A common solution is to just “add” Player.Count to your modulo result if it’s negative. So if the result is “-1” and you add Player.Count you actually get “Player.Count - 1”. Of course since we need an if statement anyways we don’t need to do the modulo since you always just decrement by 1. However a more general solution is this:

int w = i % Player.Count;
if (w < 0)
    w += Player.Count;

This should works properly for any integer number i and it will be wrapped properly on both ends.

Some examples with a Count of “5”:

//   i   | i%c |   w   | c 
//-------|-----|-------|---
//  11   |  1  |   1   | 5 
//   3   |  3  |   3   | 5 
//   2   |  2  |   2   | 5 
//   1   |  1  |   1   | 5 
//   0   |  0  |   0   | 5 
//  -1   | -1  |   4   | 5 
//  -2   | -2  |   3   | 5 
//  -3   | -3  |   2   | 5 
//  -4   | -4  |   1   | 5 
//  -5   |  0  |   0   | 5 
//  -6   | -1  |   4   | 5 
//  -7   | -2  |   3   | 5