Specify the search mode to use:

1 - Perform a search starting at the first item. This is the default.

-1 - Perform a reverse search starting at the last item.

2 - Perform a binary search that relies on lookup_array being sorted in ascending order. If not sorted, invalid results will be returned.

-2 - Perform a binary search that relies on lookup_array being sorted in descending order. If not sorted, invalid results will be returned.