module V = struct
  type t = { id : string; repr : string }
  let dump ppf t =
    let r = if t.repr = t.id then "" else Format.sprintf ";repr=%s" t.repr in
    Format.fprintf ppf "{id=%s;%s}" t.id r
  let compare x y = Pervasives.compare x.id y.id
  let equal x y = Pervasives.compare x.id y.id = 0
  let hash x = Hashtbl.hash x.id
  let check _ = ()

  let make_id ?repr id =
    match repr with
    |None -> { id = id ; repr = id }
    |Some r -> { id = id ; repr = r }
end

type var = [ `Var of V.t ]
module VAR = struct
  type t = var
  let dump ppf (`Var x) = Format.fprintf ppf "%a" V.dump x
  let compare (`Var x) (`Var y) = V.compare x y
  let equal v1 v2 = (compare v1 v2) = 0
  let hash (`Var x) = V.hash x
  let check _ = ()
end
include VAR

let id (`Var x) = x.V.id
let pp ppf (`Var x) = Format.fprintf ppf "'%s" x.V.repr

let mk ?repr id = `Var (V.make_id ?repr id)
let fresh : ?pre: string -> unit -> [> var ] =
  let counter = ref 0 in
  fun ?(pre="_fresh_") -> fun _ ->
    let id = (Printf.sprintf "%s%d" pre !counter) in
    let v = mk id in
    incr counter;
    v
;;

module Set = struct
  include SortedList.Make(VAR)
  let dump ppf s = Utils.pp_list ~sep:";" ~delim:("{","}") VAR.dump ppf (get s)
  let pp ppf s = Utils.pp_list ~sep:";" ~delim:("{","}") pp ppf (get s)
  let printf = pp Format.std_formatter
  let union = cup
  let inter = cap
  let cardinal = length
  let mem t v = mem v t
  let fold = fold
end

type 'a pairvar = [ `Atm of 'a | var ]
module type MAKE = functor (X : Custom.T) -> Custom.T with type t = X.t pairvar

module Make (X : Custom.T) = struct
  type t = X.t pairvar
  let hash = function `Atm t -> X.hash t | `Var x -> V.hash x
  let check = function `Atm t -> X.check t | `Var _ -> ()
  let compare t1 t2 =
    match t1,t2 with
    |`Var x, `Var y -> compare (`Var x) (`Var y)
    |`Atm x, `Atm y -> X.compare x y
    |`Var _, `Atm _ -> -1
    |`Atm _, `Var _ -> 1

  let equal t1 t2 = (compare t1 t2) = 0

  let dump ppf = function
    |`Atm x -> X.dump ppf x
    |`Var x -> dump ppf (`Var x)
end