Remove any given character in a string just using recursion

any.ex

defmodule Any do
  def remove(str, char) do
    remove("", str, char)
  end
  def remove(newstr, << char :: binary-size(1), rest :: binary >>, char) do
    remove(newstr, rest, char)
  end
  def remove(newstr, << first :: binary-size(1), rest :: binary >>, char) do
    remove(newstr <> first, rest, char)
  end
  def remove(newstr, <<>>, _char), do: newstr
end

any_test.exs

defmodule AnyTest do
  use ExUnit.Case
  test "remove any given characters from a string" do
    assert Any.remove("Elixir", "x") === "Eliir"
    assert Any.remove("Elixir", "E") === "lixir"
    assert Any.remove(" E l i x i r", " ") === "Elixir"
  end
end