convert.ml

type 'a jsont =
  | String : string jsont
  | List_of : 'a jsont -> 'a list jsont

let rec convert (type el) (t : el jsont) x : el option = 
  match t with
  | String ->
    begin match x with
    | `String (s : string) -> Some s
    | _ -> None
    end
  | List_of yt ->
    begin match x with
    | `List ys ->
      Some (List.map (convert yt) ys)
    | _ -> None
    end