Initial import of l3c

[snipe.git] / trans / temp.sml

(* L3 Compiler
 * Temporaries
 * Author: Kaustuv Chaudhuri <kaustuv+@cs.cmu.edu>
 * Modified: Alex Vaynberg <alv@andrew.cmu.edu>
 * Modified: Frank Pfenning <fp@cs.cmu.edu>
 *)

signature TEMP = 
sig
  type temp

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

structure Temp :> TEMP = 
struct
  type temp = int * string

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

  fun name (t,s) = "+t" ^ Int.toString t ^ "[" ^ s ^ "]"
  fun compare ((t1,_),(t2,_)) = Int.compare (t1,t2)

  fun eq ((t1,_), (t2,_)) = t1 = t2
end