     {acc, grapheme <> rest}
 
   @doc """
-  Converts all characters on the given string to uppercase.
+  Converts all characters in the given string to uppercase.
 
   ## Examples
 

  defdelegate next_grapheme(string), to: String.Graphemes

  @doc """
  Returns the first grapheme from an utf8 string,
  `nil` if the string is empty.

  ## Examples

  defdelegate upcase(binary), to: String.Unicode

  @doc """
  Converts all characters in the given string to lowercase.

  ## Examples

