Elixir library: add support to String.Chars protocol to Enum.join

Now `Enum.join([1, 2, 3], ",")` is allowed.

Signed-off-by: Davide Bettio <davide@uninstall.it>

CHANGELOG.md

@@ -12,7 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Elixir standard library modules
 - ESP32: `--boot` option to mkimage.sh tool
 - Add `erlang:atom_to_binary/1` that is equivalent to `erlang:atom_to_binary(Atom, utf8)`
-- Support for Elixir `String.Chars` protocol
+- Support for Elixir `String.Chars` protocol, now functions such as `Enum.join` are able to take
+also non string parameters (e.g. `Enum.join([1, 2], ",")`
 - Support for Elixir `Enum.at/3`
 
 ### Changed

libs/exavmlib/lib/Enum.ex

@@ -448,12 +448,12 @@ defmodule Enum do
   end
 
   @doc """
-  Joins the given enumerable into a binary using `joiner` as a
+  Joins the given `enumerable` into a binary using `joiner` as a
   separator.
 
   If `joiner` is not passed at all, it defaults to the empty binary.
 
-  All items in the enumerable must be convertible to a binary,
+  All elements in the `enumerable` must be convertible to a binary,
   otherwise an error is raised.
 
   ## Examples
@@ -468,6 +468,12 @@ defmodule Enum do
   @spec join(t, String.t()) :: String.t()
   def join(enumerable, joiner \\ "")
 
+  def join(enumerable, "") do
+    enumerable
+    |> map(&entry_to_string(&1))
+    |> IO.iodata_to_binary()
+  end
+
   def join(enumerable, joiner) when is_binary(joiner) do
     reduced =
       reduce(enumerable, :first, fn
@@ -669,6 +675,7 @@ defmodule Enum do
   @compile {:inline, entry_to_string: 1, reduce: 3}
 
   defp entry_to_string(entry) when is_binary(entry), do: entry
+  defp entry_to_string(entry), do: String.Chars.to_string(entry)
 
   ## drop
 

tests/libs/exavmlib/Tests.ex

@@ -91,6 +91,8 @@ defmodule Tests do
 
     # Enum.join
     "1, 2, 3" = Enum.join(["1", "2", "3"], ", ")
+    "1, 2, 3" = Enum.join([1, 2, 3], ", ")
+    "123" = Enum.join([1, 2, 3], "")
 
     # Enum.reverse
     [4, 3, 2] = Enum.reverse([2, 3, 4])