Added an example and explaination for using an optional path scope for the locale

railties/guides/source/i18n.textile

@@ -231,6 +231,17 @@ end
 
 Now, when you call the +books_path+ method you should get +"/en/books"+ (for the default locale). An URL like +http://localhost:3001/nl/books+ should load the Netherlands locale, then, and following calls to +books_path+ should return +"/nl/books"+ (because the locale changed).
 
+If you don't want to force the use of a locale in your routes you can use an optional path scope (donated by the use brackets) like so:
+
+<ruby>
+# config/routes.rb
+scope "(:locale)", :locale => /en|nl/ do
+  resources :books
+end
+</ruby>
+
+With this approach you will not get a +Routing Error+ when accessing your resources such as +http://localhost:3001/books+ without a locale. This is useful for when you want to use the default locale when one is not specified.
+
 Of course, you need to take special care of the root URL (usually "homepage" or "dashboard") of your application. An URL like +http://localhost:3001/nl+ will not work automatically, because the +root :to => "books#index"+ declaration in your +routes.rb+ doesn't take locale into account. (And rightly so: there's only one "root" URL.)
 
 You would probably need to map URLs like these: