(** All the types used in the spreadsheet. *)

exception Error

type cell = (int * int) * (bool * bool)

type ident = UTF8.t

type types =
  | Num  : Num.num * (UTF8.t option) -> types     (** A number *)
  | Str  : UTF8.t -> types      (** A string *)
  | Date : Num.num -> types     (** A date in julian day *)

  | Undefined : types           (** The content is not defined *)
  | Bool : bool -> types        (** A boolean *)
  | List : types list -> types  (** List with heterogenous datas *)

type refs =
  | Cell of cell                (** A cell *)
  | Range of cell * cell        (** An area of cells *)

type expression =
  | Value of types                  (** A direct value *)
  | Ref of refs                     (** A reference to another cell *)
  | Call of ident * expression list (** A call to a function *)
  | Expression of expression        (** An expression *)

(** Result from a computation *)
type result =
  | Result of types
  | Error of exn

module Type : sig

  val (=) : types -> types -> bool

  val show: UTF8.Buffer.buffer -> types -> unit

end

module Refs : sig

  val collect: refs -> (int * int) list
  
  val shift: (int * int) -> refs -> refs

end

val show_expr: UTF8.Buffer.buffer -> expression -> unit

module Result : sig

  val (=) : result -> result -> bool

  val show: result -> UTF8.t

end