This reminds me quite a bit of this article: http://blog.moertel.com/posts/2006-10-18-a-type-based-solution-to-the-strings-problem.html http://blog.moertel.com/

This reminds me quite a bit of this article: http://blog.moertel.com/posts/2006-10-18-a-type-based-solution-to-the-strings-problem.html http://blog.moertel.com/posts/2006-10-18-a-type-based-soluti..., although Haskell's type system is likely much better for expressing this sort of constraint.