It is also used in many places to avoid having to do boundry checks of the used variables.
/ Martin Nilsson (har bott i google)
Previous text:
2003-03-05 23:34: Subject: Re: negative indices in array ranges
Afaik it's primarily to make it possible to remove an element i with arr[..i-1]+arr[i+1..] without having to bother with special cases for the first (and last) elements.
/ Martin Stjernholm, Roxen IS