Specs

chunk_while(
  t(),
  acc(),
  (element(), acc() -> {:cont, chunk, acc()} | {:cont, acc()} | {:halt, acc()}),
  (acc() -> {:cont, chunk, acc()} | {:cont, acc()})
) :: Enumerable.t()
when chunk: any()

Chunks the enumerable with fine grained control when every chunk is emitted.

chunk_fun receives the current element and the accumulator and must return:

• {:cont, chunk, acc} to emit a chunk and continue with the accumulator
• {:cont, acc} to not emit any chunk and continue with the accumulator
• {:halt, acc} to halt chunking over the enumerable.

after_fun is invoked with the final accumulator when iteration is finished (or halted) to handle any trailing elements that were returned as part of an accumulator, but were not emitted as a chunk by chunk_fun. It must return:

• {:cont, chunk, acc} to emit a chunk. The chunk will be appended to the list of already emitted chunks.
• {:cont, acc} to not emit a chunk

The acc in after_fun is required in order to mirror the tuple format from chunk_fun but it will be discarded since the traversal is complete.

Returns a list of emitted chunks.

Examples

iex> chunk_fun = fn element, acc ->
...>   if rem(element, 2) == 0 do
...>     {:cont, Enum.reverse([element | acc]), []}
...>   else
...>     {:cont, [element | acc]}
...>   end
...> end
iex> after_fun = fn
...>   [] -> {:cont, []}
...>   acc -> {:cont, Enum.reverse(acc), []}
...> end
iex> Enum.chunk_while(1..10, [], chunk_fun, after_fun)
[[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]
iex> Enum.chunk_while([1, 2, 3, 5, 7], [], chunk_fun, after_fun)
[[1, 2], [3, 5, 7]]