open Core

type t = int * string [@@deriving show]

let mk =
  let table = String.Table.create () in
  let n = ref (-1) in
  function
  | name -> (
    match Hashtbl.find table name with
    | Some x -> (x, name)
    | None -> (
        incr n ;
        match Hashtbl.add table ~key:name ~data:!n with
        | `Duplicate -> failwith "Must not happend since .find failed"
        | `Ok -> (!n, name) ) )

let name (_, s) = s

let compare s1 s2 = String.compare (snd s1) (snd s2)

let equal s1 s2 = (Pervasives.compare (fst s1) (fst s2)) = 0

module Ord = struct
  type symbol = t

  type t = symbol

  let compare (x0, _) (x1, _) = Pervasives.compare x0 x1

  let t_of_sexp tuple = Tuple2.t_of_sexp Int.t_of_sexp String.t_of_sexp tuple

  let sexp_of_t tuple = Tuple2.sexp_of_t Int.sexp_of_t String.sexp_of_t tuple
end

module Table = Map.Make (Ord)