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A dependency-free utility library containing 100+ useful functions.

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moar lib tuple.ex
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lib/tuple.ex 

defmodule Moar.Tuple do

  # @related [test](/test/tuple_test.exs)



  @moduledoc "Tuple-related functions."



  @doc """

  Converts a list of tuples to a single tuple whose first element is the first element of each tuple in

  the list (which must all be the same), and whose second element is a list containing the second elements

  of each tuple in the list.



  Raises if the list contains tuples whose first elements are not all the same.



  ```elixir

  iex> Moar.Tuple.from_list!([{:ok, :a}, {:ok, :b}])

  {:ok, [:a, :b]}



  iex> Moar.Tuple.from_list!([{:a, 1}, {:a, 2}, {:a, 3}])

  {:a, [1, 2, 3]}



  iex> Moar.Tuple.from_list!([{:a, 1}, {:b, 2}, {:a, 3}])

  ** (RuntimeError) Expected all items in the list to have have the same first element, but got: [:a, :b]

  ```

  """

  @spec from_list!([any()]) :: {any(), [any()]}

  def from_list!(list) do

    {keys, values} = Enum.unzip(list)



    case Enum.uniq(keys) do

      [key] -> {key, values}

      keys -> raise "Expected all items in the list to have have the same first element, but got: #{inspect(keys)}"

    end

  end



  @doc """

  Reduces a list of tuples to map where values are consolidated by the first element of each input tuple.

  Optionally accepts a list of default keys, whose values will be `[]` if not found in the input.



  ```elixir

  iex> Moar.Tuple.reduce([{:ok, 1}, {:ok, 2}])

  %{ok: [1, 2]}



  iex> Moar.Tuple.reduce([{:ok, 1}, {:ok, 2}, {:error, 3}, {:ok, 4}])

  %{ok: [1, 2, 4], error: [3]}



  iex> Moar.Tuple.reduce([{:ok, 1}, {:ok, 2}], [:ok, :warning, :error])

  %{ok: [1, 2], warning: [], error: []}

  ```

  """

  @spec reduce([any()], [any()]) :: map()

  def reduce(list, defaults \\ []) do

    reduced =

      list

      |> Enum.reduce(%{}, fn {k, v}, acc -> Map.update(acc, k, [v], fn list -> [v | list] end) end)

      |> Map.new(fn {k, v} -> {k, Enum.reverse(v)} end)



    Enum.reduce(defaults, reduced, fn default, acc -> Map.put_new(acc, default, []) end)

  end

end