koos42

Keybase proof

I hereby claim:

• I am koos42 on github.
• I am koos42 (https://keybase.io/koos42) on keybase.
• I have a public key ASCd1eCAzk4EyQYOvH5zn9CDutJ7ZmiKNJl5aFURYyUbrAo

To claim this, I am signing this object:

koos42

defmodule Example do
  @doc """
  iex> stable_group_by([c: 1, b: 1, b: 2, b: 3, a: 1, a: 2, a: 3], &elem(&1, 0))
  %{a: [a: 1, a: 2, a: 3], b: [b: 1, b: 2, b: 3], c: [c: 1]}
  """
  def stable_group_by(list, mapper_fun) do
    list
    |> Enum.reduce(%{}, fn(item, acc) ->
         Map.update(acc, mapper_fun.(item), [item], fn(sub_list)-> [ item | sub_list ] end)
       end)

koos42

# Do my homework:
# Write a method that takes an array of elements where each element is either of
# type A or type B and returns an array of arrays where all the sub arrays are 
# filled with only type A or type B and preserve the order.

# example:  [a, a, b, a, a, a, b, b, a] => [[a, a], [b], [a, a, a], [b, b], [a]]

# these solutions don't enforce the constraint that there be only two types of things.

# group things