pattern matching on 0.0 is equivalent to matching only on +0.0 from E…

…rlang/OTP 27+. Instead you must match on +0.0 or -0.0

lib/ex_xirr.ex

@@ -174,7 +174,7 @@ defmodule ExXirr do
 
   @spec calculate(atom(), list(), float(), float(), integer()) ::
           {:ok, float()} | {:error, String.t()}
-  defp calculate(:xirr, _, 0.0, rate, _), do: {:ok, Float.round(rate, 6)}
+  defp calculate(:xirr, _, acc, rate, _)  when acc in [-0.0, +0.0], do: {:ok, Float.round(rate, 6)}
   defp calculate(:xirr, _, _, -1.0, _), do: {:error, "Could not converge"}
   defp calculate(:xirr, _, _, _, 300), do: {:error, "I give up"}
 

lib/legacy_finance.ex

@@ -102,7 +102,7 @@ defmodule LegacyFinance do
     acc * first_value_sign(dates_values)
   end
 
-  defp calculate(:xirr, _date_values, 0.0, {rate, _bottom, _upper}, _tries) do
+  defp calculate(:xirr, _date_values, acc, {rate, _bottom, _upper}, _tries) when acc in [-0.0, +0.0] do
     {:ok, Float.round(rate, 6)}
   end