Question

I got an object (called tempEnemy) which is flying around and shooting.
The problem is that I can’t keep the value tempEnemy.rotateTo positive, i.e.
it shall be between 0 and 359 degrees. Currently rotateTo ranges from:
rotateTo < 0 (bug) && rotateTo > 0 && rotateTo > 359 (bug).

tempEnemy.dX = tempEnemy.destX - tempEnemy.x;
tempEnemy.dY = tempEnemy.destY - tempEnemy.y;

//I added 180 because my tempEnemy object was looking and shooting to the wrong direction
tempEnemy.rotateTo = (toDegrees(getRadians(tempEnemy.dX, tempEnemy.dY))) + 180; 

if (tempEnemy.rotateTo > tempEnemy.frame + 180) tempEnemy.rotateTo -= 360;
if (tempEnemy.rotateTo < tempEnemy.frame - 180) tempEnemy.rotateTo += 360;

tempEnemy.incFrame = int((tempEnemy.rotateTo - tempEnemy.frame) / tempEnemy.rotateSpeed);

Answer 1

You can always use the modulo operator (%) to keep a value positive. The module calculates the rest of a division.

E.g. (example works with integers there for a division always has a left over.)

19 % 5 = 4

Because in the number 19 5 only fits 3 times (3 * 5 = 15,, 4 * 5 = 20,, 20 is too high) the left over is 4 (19 - 15). That is the modulo.

Extra examples:

7 % 3 = 1
15 % 4 = 3
21 % 9 = 3

The output of a modulo operation is never higher then the right hand operator – 1 There for it is perfect for your problem.

If your object is rotated 1234 degrees,, then operate it with a modulo 360 to get the respective number between 0 and 360 for it.

1234 % 360 = 154

Other more easier examples:

720 % 360 = 0
360 % 360 = 0
540 % 360 = 180
-180 % 360 = 180
-720 % 360 = 0
-540 % 360 = 180