(* Title:  BaseDefinitions/rewrite-order.sml

    Author: Walther Neuper

    (c) due to copyright terms

 TODO: use "Rewrite_Ord" for renaming identifiers.

 *)

 signature REWRITE_ORDER =

 sig

   type subst

   val e_rew_ord': Rule_Def.rew_ord';

   val dummy_ord: Rule_Def.rew_ord_

   val e_rew_ord: Rule_Def.rew_ord_

   type rew_ord = Rule_Def.rew_ord

   val e_rew_ordX: rew_ord

   type rew_ord' = Rule_Def.rew_ord'

   val rew_ord': (rew_ord' * (subst -> term * term -> bool)) list Unsynchronized.ref

   val assoc_rew_ord: string -> subst -> term * term -> bool

 (* ---- for tests only: shifted from below to remove the Warning "unused" at fun.def. --------- *)

   (*NONE*)

 (*/-------------------------------------------------------- ! aktivate for Test_Isac BEGIN ---\* )

   (*NONE*)

 ( *\--- ! aktivate for Test_Isac END ----------------------------------------------------------/*)

 end

 (**)

 structure Rewrite_Ord(**): REWRITE_ORDER(**) =

 struct

 (**)

 val e_rew_ord' = "e_rew_ord" : Rule_Def.rew_ord';

 type rew_ord_ = Rule_Def.rew_ord_;

 type subst = (term * term) list;

 fun dummy_ord (_: subst) (_: term, _: term) = true;

 val e_rew_ord_ = dummy_ord;

 type rew_ord = (*rew_ord' * rew_ord_;*) Rule_Def.rew_ord

 val e_rew_ord = dummy_ord; (* TODO.WN071231 clarify identifiers..e_rew_ordX*)

 val e_rew_ordX = (e_rew_ord', e_rew_ord_)

 type rew_ord' = Rule_Def.rew_ord'

 (* rewrite orders, also stored in 'type met' and type 'and rls'

   The association list is required for 'rewrite.."rew_ord"..' *)

 val rew_ord' = Unsynchronized.ref

   ([("e_rew_ord", e_rew_ord), ("dummy_ord", dummy_ord)]

 	: (rew_ord' *    (* the key for the association list         *)

 	    (subst 	    (* the bound variables - they get high order*)

 	     -> (term * term) (* (t1, t2) to be compared                  *)

 	     -> bool))        (* if t1 <= t2 then true else false         *)

 		list);              (* association list                         *)

 fun assoc' ([], key) = raise ERROR ("ME_Isa: \"" ^ key ^ "\" not known")

   | assoc' ((keyi, xi) :: pairs, key) =

     if key = keyi then SOME xi else assoc' (pairs, key);

 fun assoc_rew_ord ro = ((the o assoc') (! rew_ord',ro))

   handle _ => raise ERROR ("ME_Isa: rew_ord '" ^ ro ^ "' not in system");

 end