l1 and
l2 be defined analogously
to the case when rSum was considered
in the text. This time, we have only one formal parameter
and no local variables. The stack element format is
(address to return to, value of n)
[]
[(l1, 0)]
[(l1, 0), (l2, 3)]
[(l1, 0), (l2, 3), (l2, 2)]
[(l1, 0), (l2, 3), (l2, 2),
(l2, 1)]
[(l1, 0), (l2, 3), (l2, 2)]
[(l1, 0), (l2, 3)]
[(l1, 0)]
[]