Specs

unfold(acc(), (acc() -> {element(), acc()} | nil)) :: Enumerable.t()

Emits a sequence of values for the given accumulator.

Successive values are generated by calling next_fun with the previous accumulator and it must return a tuple with the current value and next accumulator. The enumeration finishes if it returns nil.

Examples

iex> Stream.unfold(5, fn
...>   0 -> nil
...>   n -> {n, n - 1}
...> end) |> Enum.to_list()
[5, 4, 3, 2, 1]