elixir_macros.ex

defmodule MyFunc do 
  
  defmacro dynamic_fn(n) do
    quote do
      def unquote(:"multiply_#{n}")(arg) do
        unquote(n) * arg
      end
    end
  end

  defmacro dynamic_fn2(n) do
    quote bind_quoted: [n: n] do
      def unquote(:"multiply_#{n}")(arg) do 
        unquote(n) * arg
      end
    end
  end

  defmacro dynamic_fn3(name) do
    quote bind_quoted: [name: name] do 
      def unquote(name)(), do: unquote(name)
    end
  end
end

defmodule TestFunc do
  require MyFunc

  MyFunc.dynamic_fn(2) # works fine
  #[6, 7] |> Enum.each(&MyFunc.dynamic_fn/1) # throws error

  MyFunc.dynamic_fn2(4) # works fine
  #[8, 9] |> Enum.each(&MyFunc.dynamic_fn2/1) # throws error
  
  MyFunc.dynamic_fn3(:first_fn) # works fine
  [:second_fn, :third_fn] |> Enum.each(&MyFunc.dynamic_fn3/1) # works fine

end