1 files changed, 1 insertions, 0 deletions
diff --git a/ppc.sig b/ppc.sig
index 53d4ed2..210489b 100644
--- a/ppc.sig
+++ b/ppc.sig
@@ -24,6 +24,7 @@ signature PPC = sig
   val debugPrint: string -> string list -> unit
 
   val ? : (int, 'a, 'b, 'c) a1printer
+  val ?? : int -> string
   val psid: int -> 'a acc -> unit
   val Ptk: (T.token, 'a, 'b, 'c) a1printer
   val PtkPos: (tkPos, 'a, 'b, 'c) a1printer