Roll items on the stack
_stk_roll (Integer_Type n);
This function may be used to alter the arrangement of objects on the
stack. Specifically, if the integer n is positive, the top
n items on the stack are rotated up. If
n is negative, the top abs(n) items on the stack are
rotated down.
If the stack looks like:
item-0
item-1
item-2
item-3
where item-0 is at the top of the stack, then
_stk_roll(-3) will change the stack to:
item-2
item-0
item-1
item-3
This function only has an effect for abs(n) > 1.
_stkdepth, _stk_reverse, _pop_n, _print_stack