type pos = Lexing.position * Lexing.position
type ('a, 'b) variable = { pos : 'a; name : string; index : 'b option }

module Expression = struct
  type 'a obs
  type repr = unit

  type variable = { pos : pos; name : string; index : repr option }
  (** 
      Describe a variable, using the name in capitalized text, and an optionnal
      index.

      If missing, the index should be considered as [0].
   *)

  let ident : variable -> repr = fun _ -> ()

  (*
        Basic values, text, number…
   *)

  let integer : pos -> string -> repr = fun _ _ -> ()
  let literal : pos -> string -> repr = fun _ _ -> ()

  (** Call a function. The functions list is hardcoded in lib/lexer.mll *)
  let function_ : pos -> T.function_ -> repr list -> repr = fun _ _ _ -> ()

  (** Unary operator like [-123] or [+'Text']*)
  let uoperator : pos -> T.uoperator -> repr -> repr = fun _ _ _ -> ()

  (** Binary operator, for a comparaison, or an operation *)
  let boperator : pos -> T.boperator -> repr -> repr -> repr = fun _ _ _ _ -> ()
end