[snipe.git] / trans / label.sml

(* L3 Compiler
 * Labeloraries
 * Like temporaries, except more different
 * Author: Joshua Wise <jwise@cs.cmu.edu>
 *)

signature LABEL = 
sig
  type label

  val reset : unit -> unit      (* resets label numbering *)
  val new : unit -> label       (* returns a unique new label *)
  val name : label -> string    (* returns the name of a label *)
  val compare : label * label -> order (* comparison function *)
end

structure Label :> LABEL = 
struct
  type label = int

  local
    val counter = ref 1
  in
    (* warning: calling reset() may jeopardize uniqueness of labels! *)
    fun reset () = ( counter := 1 )
    fun new () = !counter before ( counter := !counter + 1 )
  end

  fun name t = ".L" ^ Int.toString t
                      
  fun compare (t1,t2) = Int.compare (t1,t2)
end