open Core.Std

exception Bad_id of string

module type empty = sig end

module type id = sig
    type t
    val of_string : string -> t
    val to_string : t -> string
  end

module StrId (E : empty) : id =
  struct
    type t = string
    let of_string x = x
    let to_string x = x
  end

module TypeId = StrId (struct end)
module ServiceId = StrId (struct end)