Beging the Ord protocol

ord.ex

defprotocol Ord do
  @doc """
    iex> Ord.compare("a", "b")
    :EQ
    iex> Ord.compare("a", "b", type: :alphabetical)
    :LT
  """
  def compare(a, b, opts \\ [])
  def lt(a, b)
  def lte(a, b)
  def gt(a, b)
  def gte(a, b)
  def max(a, b)
  def min(a, b)
end

defimpl Ord, for: BitString do
  def compare(a, b, opts) do
    case Keyword.get(opts, :type, :length) do
      :alphabetical -> string_compare_alphabetical_order(a, b)
      _ -> string_compare_length(a, b)
    end
  end

  defp string_compare_length(a, b) do
    cond do
      String.length(a) < String.length(b) -> :LT
      String.length(a) == String.length(b) -> :EQ
      true -> :GT
    end
  end

  defp string_compare_alphabetical_order(a, b) do
    cond do
      a < b -> :LT
      a == b -> :EQ
      true -> :GT
    end
  end
end

ord_test.exs

defmodule OrdTest do
  use ExUnit.Case
  doctest Ord
end