[Haskell-cafe] Polymorphic variants

Does Haskell have anything similar to OCaml's polymorphic variants? They act as inferred sum types: # let rec eval = function | `Int n -> n | `Add(f, g) -> eval f + eval g | `Mul(f, g) -> eval f * eval g;; val eval : ([< `Add of 'a * 'a | `Int of int | `Mul of 'a * 'a ] as 'a) -> int = <fun> -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. OCaml for Scientists http://www.ffconsultancy.com/products/ocaml_for_scientists/?e