+ absurd_URIs_ref := default_absurd_URIs;
+ nat_URIs_ref := default_nat_URIs
+;;
+
+let stack = ref [];;
+
+let push () =
+ stack := (!eq_URIs_ref, !true_URIs_ref, !false_URIs_ref, !absurd_URIs_ref,
+ !nat_URIs_ref
+ )::!stack;
+ reset_defaults ()
+;;