Elixir：流入跑步

Question

I'd like to stream a list (pre-sorted) such as

[1,1,1,2,2,2,2,2,2,3,3,4]

so it becomes split into runs like this

[[1,1,1],[2,2,2,2,2,2],[3,3],[ 4]]

is there a neat way of doing this?

I've been studying: Stream.transform , Stream.take_while , Enum.split_while , Enum.partition , Enum.flat_map_reduce

In the end I need to extend the answer from lists of numbers to tuples that contain numbers

Answer 1

I think Enum.chunk_by/2 (there's also a Stream version) does the trick:

iex(1)> [1,1,1,2,2,2,2,2,2,3,3,4] |> Enum.chunk_by(fn(x) -> x end)
[[1, 1, 1], [2, 2, 2, 2, 2, 2], [3, 3], [4]]

Or with capture syntax:

iex(2)> [1,1,1,2,2,2,2,2,2,3,3,4] |> Enum.chunk_by(&(&1))

Answer 2

I would use Stream.chunk_by :

Stream.chunk_by(nums, fn num -> num end) |> Enum.to_list
#> [[1,1,1], [2,2,2,2,2,2], [3,3], [4]]]

Easy!