Example of implementing equality

equality.exs

defmodule EqualityExample do
  import Kernel, except: [==: 2]

  defprotocol Eq do
    def eq?(x, y)
  end

  defimpl Eq, for: Integer do
    def eq?(x, y) when is_integer(y) do
      IO.inspect("#{x} == #{y}")
      IO.inspect(Kernel.==(x, y))
    end
  end

  defmacro __using__(_) do
    quote do
      import Kernel, except: [==: 2, +: 2, <: 2]
      import EqualityExample
      alias EqualityExample.Eq
    end
  end

  def x == y, do: Eq.eq?(x, y)
  def x + y, do: add(x, y)

  def add(x, y) do
    IO.inspect("#{x} + #{y}")
    IO.inspect(Kernel.+(x, y))
  end
end

defmodule Context do
  def test(x) when x == 1 do
    use EqualityExample
    1 == 2
    1 + (2 + 3)
    1 == "a"
  end
end

Context.test(1)