]> Dawid Toton wrote: > Could anybody explain why it's impossible to have type classes in OCaml? I don't think it's impossible - but I believe that if you introduce type classes then you "damage" Hindley-Milner type inference and you can no longer derive a principal typing for an arbitrary ML expression without resorting to type annotations. Whether this is a problem or not is a matter of taste - but it does make the language harder to call "ML" if you lose one of its central features! That said, there are of course two big features (objects and polymorphic variants) in OCaml already which do require annotations. David