Invoke Elixir Functions with Apply

I had a weird problem yesterday: I wanted to pass a function into another function and then invoke it, all for the sake of a friendly API.

Elixir's apply to the rescue. Here's the rough implementation.

defmodule Example do
  def do_things(index, rotation, operator) do
    apply(Kernel, operator, [index, rotation])
  end
end

iex> Example.do_things(10, 20, :+)
30
iex> Example.do_things(10, 20, :-)
-10

apply also accepts your own functions:

defmodule Example do
  def do_things(index) do
    apply(__MODULE__, :make_bigger, [index])
  end

  def make_bigger(a) do
    a * 10000
  end
end

iex> Example.do_things(100)
1000000

The module name (Example) will work in place of __MODULE__, if you prefer. This seems like a pretty powerful feature.