Does anyone know what's going on with ï for negative input vs negative hardcoded/calculated values? I.e. 0.04(ï results in -1, but ï with input -0.04 results in 0. :S

I'm not sure exactly what the problem is but the only difference is that in the first case the stack is [0.04] and in the second case, the stack is ["-0.04"]

Perhaps ï doesn't like strings?

I think the problem may lie somewhere in here:

def to_integer(value) do
    cond do
        value == true -> 1
        value == false -> 0
        is_integer(value) -> value
        is_float(value) -> round(Float.floor(value))
        is_iterable(value) -> value |> Stream.map(&to_integer/1)
        true ->
            case Integer.parse(to_string(value)) do
                :error -> value
                {int, string} ->
                    cond do
                        string == "" -> int
                        Regex.match?(~r/^\.\d+$/, string) -> int

After line 75 in functions.exs