The Challenge:
To construct a function to return a section of a list, with behaviour akin to the substr function (with the exception of a zero-based index)
(SubList <list> <start> [<length>])
Examples:
(SubList '(0 1 2 3 4 5) 2 3)
>> (2 3 4)
(SubList '(0 1 2 3 4 5) 2 nil)
>> (2 3 4 5)
(SubList '(0 1 2 3 4 5) 6 3)
>> nil