Hi,

I'm wondering if one can have an ascociative container, like a Hashtbl.t
with dependent types (GADTs as the key, value depending on the key).
Something like this:

module H = struct
  type ('a, 'b) t = ('a, 'b) Hashtbl.t
  let create : type a b . int -> (a b, a) t =
                 fun x -> Hashtbl.create x
  let add : type a b . (a b, a) t -> a b -> a -> unit =
              fun h k v -> Hashtbl.add h k v
  let find : type a b . (a b, a) t -> a b -> a =
              fun h k -> Hashtbl.find h k
end

BUT:

    let create : type a b . int -> (a b, a) t =
                                    ^^^
Error: Unbound type constructor b


Is there some special syntax I'm missing or is it simply impossible to
declare such a container in the abstract?