@spec chunk(t, pos_integer, pos_integer, t | nil) :: [list]
def chunk(enumerable, count, step, leftover \\ nil)
when is_integer(count) and count > 0 and is_integer(step) and step > 0 do
limit = :erlang.max(count, step)
{acc, {buffer, i}} =
reduce(enumerable, {[], {[], 0}}, R.chunk(count, step, limit))
if is_nil(leftover) || i == 0 do
:lists.reverse(acc)
else
buffer = :lists.reverse(buffer, take(leftover, count - i))
:lists.reverse([buffer | acc])
end
end