Updated attach_function macro to use dynamic number of arguments

lib/ffi/library.ex

@@ -8,15 +8,31 @@ defmodule FFI.Library do
   end
 
   defmacro attach_function(name, arguments, return_type) do
+    argument_names = make_argument_names(arguments)
+
     quote do
-      def unquote(name)(params) do
+      def unquote(name)(unquote_splicing(argument_names)) do
         definition = {ffi_lib,
                       unquote(name),
                       unquote(arguments),
                       unquote(return_type)}
 
-        FFI.call(definition, params)
+        FFI.call(definition, [unquote_splicing(argument_names)])
       end
     end
   end
+
+  defp make_argument_names(arguments) do
+    arguments
+    |> Enum.with_index
+    |> Enum.map(&make_argument_name/1)
+  end
+
+  defp make_argument_name({_type, index}) do
+    variable_name = [?a + index]
+                    |> to_string
+                    |> String.to_atom
+
+    Macro.var(variable_name, nil)
+  end
 end