function gives "2nd argument: not valid character data" error

Question

I am new to elixir and I am trying to make a recursive anonymous function, but for some reason my anynymous function that works on it's own as expected throws me "2nd argument: not valid character data (an iodata term)" error.

Here is code:

calcTip = fn bill ->
  if bill >= 50 and bill <= 300, do: bill * 0.15, else: bill * 0.2
end

bills = [ 22, 295, 176, 440, 37, 105, 10, 1100, 86, 52 ]

calcTipsAndTotals = fn index, tips, totals, recursiveFn ->
  case index < length(bills) do
    true ->
      new_tip = calcTip.(Enum.at(bills, index, 0))
      new_tips = tips ++ [new_tip]
      new_totals = totals ++ [Enum.at(new_tips, index) + Enum.at(bills, index)]
      recursiveFn.(index + 1, new_tips, new_totals, recursiveFn)
    false -> [tips, totals]
  end
end

IO.puts(
  calcTipsAndTotals.(0, [], [], calcTipsAndTotals)
)

Answer 1

If you pass a list to IO.puts, it expects the argument to be valid IO data, but the result of your function is not, it's a list of lists of floats.

The simplest fix is to use IO.inspect instead:

calcTipsAndTotals.(0, [], [], calcTipsAndTotals) |> IO.inspect()

---

Simplified example:

iex(1)> IO.puts([[1.0]])
** (ArgumentError) errors were found at the given arguments:

  * 2nd argument: not valid character data (an iodata term)

    (stdlib 4.2) io.erl:99: :io.put_chars(:standard_io, [[[1.0]], 10])
    iex:1: (file)
iex(1)> IO.inspect([[1.0]])
[[1.0]]
[[1.0]]