## Logic Bomb... Retrieving "negative" index, and wrap around an Array?

I have an indexed array full of strings.

PHP Code:
``` my_array = new Array("hello", "dear", "goodbye", "cruel", "world", "never", "noticed");  ```
I'm generating an integer elsewhere in my code which I want to use to lookup the appropriate index in my_array.
However, the number I'm passing to the [] access operator could be positive or negative, and it could be more or less than my_array.length
For Example:

PHP Code:
``` my_array[lookUpIndex] my_array[52] my_array[-2] my_array[-123]  ```
So, I need someone to help me with the equation (if possible) that I could use so that if I generate the lookUpIndex out of bounds of the Array, I would be able to "wrap" around the array and get the appropriate element.

For example:
PHP Code:
``` var lookUpIndex:int = 10; trace(my_array[lookUpIndex]); // output "cruel", also known as my_array[3]  ```
The real problem is when you get into negative numbers.
PHP Code:
``` var lookUpIndex:int = -1; trace(my_array[lookUpIndex]); // output "noticed", also known as my_array[my_array.length] var lookUpIndex:int = -7; trace(my_array[lookUpIndex]); // output "hello", also known as my_array[0] var lookUpIndex:int = -10; trace(my_array[lookUpIndex]); // output "world", also known as my_array[4]  ```
I would like 1 equation that could handle both positives and negatives, instead of having to use a conditional.

Basically, I need someone to fill in the equation below:
PHP Code:
``` var lookUpIndex:int = -128; var i:int = *some equation involving lookUpIndex* trace(my_array[i]);  ```
NOTE: Using the modulo (%) operator works fine when dealing with positive numbers...
PHP Code:
``` var lookUpIndex:int = 128; var i:int = lookUpIndex % my_array.length; trace(my_array[i]);  ```
But like I said, I'd like to come up with 1 equation that fits all positive and negative look up number scenarios.

Thanks!