a := [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
assert a#[-1] == 9
assert a#[-1..] == [9]
assert a#[..-9] == [0]
assert a#[-9..-7] == [1, 2]
assert a#[-2..] == [8, 9]