Incorrect arity. For some reason

Questions / Help
1

It’s funny, this throws an exception in REPL:

defmodule M1 do
  def f_generic(a) do
    :timer.sleep(a)
    IO.puts "sleep #{a} done"
  end

  def run do
    res = Enum.map([3000, 5000, 1000, 12000, 2000], 
                    &(Task.async(fn x -> f_generic(&1) end)))
  end
end

M1.run

Exception:

** (EXIT from #PID<0.84.0>) an exception was raised:
    ** (BadArityError) #Function<1.42455878/1 in M1.run/0> with arity 1 called with no arguments                                                              
        :erlang.apply/2                                                                                                                                       
        (elixir) lib/task/supervised.ex:85: Task.Supervised.do_apply/2                                                                                        
        (elixir) lib/task/supervised.ex:36: Task.Supervised.reply/5                                                                                           
        (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3

Ok, calling with an argument:

 M1.run(123)
** (UndefinedFunctionError) function M1.run/1 is undefined or private. Did you mean one of:

      * run/0

    M1.run(123)
2

Try this code instead:

defmodule M1 do
  def f_generic(a) do
    :timer.sleep(a)
    IO.puts "sleep #{a} done"
  end

  def run do
    res = Enum.map([3000, 5000, 1000, 12000, 2000], 
                    &Task.async(fn -> f_generic(&1) end))
  end

The task does not expect an argument.