The goal of this Kata is to return the greatest distance of index positions between matching number values in an array or 0 if there are no matching values.  
Example:
In an array with the values [0, 2, 1, 2, 4, 1] the greatest index distance is between the matching '1' values at index 2 and 5.  Executing greatestDistance against this array would return 3. (i.e. 5 - 2)  
Here's the previous example in test form:
```python
test.assert_equals(greatest_distance([0, 2, 1, 2, 4, 1]), 3)
```
This is based on a Kata I had completed only to realize I has misread the instructions.  I enjoyed solving the problem I thought it was asking me to complete so I thought I'd add a new Kata for others to enjoy.  There are no tricks in this one, good luck!
def greatest_distance(arr):
    return max(i - arr.index(x) for i,x in enumerate(arr))
def greatest_distance(arr):
    return max(i - arr.index(x) for i,x in enumerate(arr))