I wrote something to a similar effect in an earlier version of Swift. It might be of interest to readers<p><a href="http://jspha.com/posts/immutable_enumeration_in_swift/" rel="nofollow">http://jspha.com/posts/immutable_enumeration_in_swift/</a><p><a href="http://jspha.com/posts/calkin-wilf-in-swift/" rel="nofollow">http://jspha.com/posts/calkin-wilf-in-swift/</a>