Re: [Haskell-cafe] Type system trickery

David Menendez wrote:

If you don't need code that's polymorphic between Foobar HasZoo and Foobar NoZoo, you could just newtype Foobar and only export smart constructors.

Unfortunately I want to be able to print both of them out. (After all, the printing algorithm is identical whether Zoo is present or not - except that if Zoo isn't there, you don't need to handle Zoo!) Nice idea though.