type domain_item =
 | Id of string               (* literal *)
 | Symbol of string * int     (* literal, instance num *)
 | Num of int                 (* instance num *)

module OrderedDomain =
  struct
    type t = domain_item
    let compare = Pervasives.compare
  end

(* module Domain = Set.Make (OrderedDomain) *)
module Environment = Map.Make (OrderedDomain)

type codomain_item =
  string *  (* description *)
  (environment -> string -> Cic.term list -> Cic.term)
    (* environment, literal number, arguments as needed *)

and environment = codomain_item Environment.t

module type Callbacks =
  sig
    val output_html : ?append_NL:bool -> Ui_logger.html_msg -> unit
    val interactive_user_uri_choice :
      selection_mode:[`SINGLE | `MULTIPLE] ->
      ?ok:string ->
      ?enable_button_for_non_vars:bool ->
      title:string -> msg:string -> id:string -> string list -> string list
    val interactive_interpretation_choice :
      (string * string) list list -> int
    val input_or_locate_uri : title:string -> UriManager.uri
  end

let string_of_domain_item = function
  | Id s -> Printf.sprintf "ID(%s)" s
  | Symbol (s, i) -> Printf.sprintf "SYMBOL(%s,%d)" s i
  | Num i -> Printf.sprintf "NUM(instance %d)" i

let string_of_domain dom =
  String.concat "; " (List.map string_of_domain_item dom)
(*
let string_of_domain dom =
  let buf = Buffer.create 1024 in
  Domain.iter
    (fun item -> Buffer.add_string buf (string_of_domain_item item ^ "; "))
    dom;
  Buffer.contents buf
*)