diff --git a/Makefile.in b/Makefile.in
index f6320061a..7580e80d0 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -18,7 +18,7 @@
 #    59 Temple Place - Suite 330
 #    Boston, MA 02111-1307, USA
 #
-#ident "$Id: Makefile.in,v 1.7 1999/07/03 20:50:28 steve Exp $"
+#ident "$Id: Makefile.in,v 1.8 1999/07/17 22:01:13 steve Exp $"
 #
 #
 SHELL = /bin/sh
@@ -53,11 +53,12 @@ clean:
 	cd ivlpp ; make clean
 
 TT = t-null.o t-verilog.o t-vvm.o t-xnf.o
-FF = nobufz.o propinit.o sigfold.o stupid.o xnfio.o
+FF = nobufz.o propinit.o sigfold.o xnfio.o
 
-O = main.o cprop.o design_dump.o elaborate.o emit.o eval.o lexor.o mangle.o \
-netlist.o parse.o parse_misc.o pform.o pform_dump.o verinum.o verireal.o \
-target.o targets.o Module.o PExpr.o PGate.o PTask.o PWire.o Statement.o \
+O = main.o cprop.o design_dump.o elaborate.o emit.o eval.o functor.o \
+lexor.o mangle.o netlist.o parse.o parse_misc.o pform.o pform_dump.o \
+verinum.o verireal.o target.o targets.o Module.o PExpr.o PGate.o \
+PTask.o PWire.o Statement.o \
 $(FF) $(TT)
 
 Makefile: Makefile.in config.status
diff --git a/stupid.cc b/functor.cc
similarity index 52%
rename from stupid.cc
rename to functor.cc
index f254fb10a..841598f28 100644
--- a/stupid.cc
+++ b/functor.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -17,24 +17,44 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: stupid.cc,v 1.2 1998/11/13 06:23:17 steve Exp $"
+#ident "$Id: functor.cc,v 1.1 1999/07/17 22:01:13 steve Exp $"
 #endif
 
+# include  "functor.h"
 # include  "netlist.h"
 
-
-void stupid(Design*des)
+functor_t::~functor_t()
 {
 }
 
+void functor_t::signal(class Design*, class NetNet*)
+{
+}
+
+void functor_t::process(class Design*, class NetProcTop*)
+{
+}
+
+void Design::functor(functor_t*fun)
+{
+	// apply to signals
+      if (signals_) {
+	    NetNet*cur = signals_->sig_next_;
+	    do {
+		  fun->signal(this, cur);
+		  cur = cur->sig_next_;
+	    } while (cur != signals_->sig_next_);
+      }
+
+	// apply to processes
+      for (NetProcTop*idx = procs_ ;  idx ;  idx = idx->next_)
+	    fun->process(this, idx);
+}
+
 /*
- * $Log: stupid.cc,v $
- * Revision 1.2  1998/11/13 06:23:17  steve
- *  Introduce netlist optimizations with the
- *  cprop function to do constant propogation.
- *
- * Revision 1.1  1998/11/03 23:29:05  steve
- *  Introduce verilog to CVS.
+ * $Log: functor.cc,v $
+ * Revision 1.1  1999/07/17 22:01:13  steve
+ *  Add the functor interface for functor transforms.
  *
  */
 
diff --git a/functor.h b/functor.h
new file mode 100644
index 000000000..3882a4dd6
--- /dev/null
+++ b/functor.h
@@ -0,0 +1,53 @@
+#ifndef __functor_H
+#define __functor_H
+/*
+ * Copyright (c) 1999 Stephen Williams (steve@icarus.com)
+ *
+ *    This source code is free software; you can redistribute it
+ *    and/or modify it in source code form under the terms of the GNU
+ *    General Public License as published by the Free Software
+ *    Foundation; either version 2 of the License, or (at your option)
+ *    any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+#if !defined(WINNT)
+#ident "$Id: functor.h,v 1.1 1999/07/17 22:01:13 steve Exp $"
+#endif
+
+/*
+ * The functor is an object that can be applied to a design to
+ * transform it. This is different from the target_t, which can only
+ * scan the design but not transform it in any way.
+ */
+
+class Design;
+class NetNet;
+class NetProcTop;
+
+struct functor_t {
+      virtual ~functor_t();
+
+	/* Signals are scanned first. This is called once for each
+	   signal in the design. */
+      virtual void signal(class Design*des, class NetNet*);
+
+	/* This method is called for each process in the design. */
+      virtual void process(class Design*des, class NetProcTop*);
+
+};
+
+/*
+ * $Log: functor.h,v $
+ * Revision 1.1  1999/07/17 22:01:13  steve
+ *  Add the functor interface for functor transforms.
+ *
+ */
+#endif
diff --git a/main.cc b/main.cc
index 52f0e7576..d63b20858 100644
--- a/main.cc
+++ b/main.cc
@@ -19,7 +19,7 @@ const char COPYRIGHT[] =
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: main.cc,v 1.19 1999/07/10 23:29:21 steve Exp $"
+#ident "$Id: main.cc,v 1.20 1999/07/17 22:01:13 steve Exp $"
 #endif
 
 const char NOTICE[] =
@@ -80,7 +80,6 @@ extern void emit(ostream&o, const Design*, const char*);
 extern void cprop(Design*des);
 extern void propinit(Design*des);
 extern void sigfold(Design*des);
-extern void stupid(Design*des);
 extern void nobufz(Design*des);
 extern void xnfio(Design*des);
 
@@ -93,7 +92,6 @@ static struct net_func_map {
       { "nobufz",  &nobufz },
       { "propinit", &propinit },
       { "sigfold", &sigfold },
-      { "stupid",  &stupid },
       { "xnfio",   &xnfio },
       { 0, 0 }
 };
@@ -272,6 +270,9 @@ int main(int argc, char*argv[])
 
 /*
  * $Log: main.cc,v $
+ * Revision 1.20  1999/07/17 22:01:13  steve
+ *  Add the functor interface for functor transforms.
+ *
  * Revision 1.19  1999/07/10 23:29:21  steve
  *  pform even on parse errors.
  *
diff --git a/netlist.h b/netlist.h
index c4b3d75ba..c3c2b3609 100644
--- a/netlist.h
+++ b/netlist.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: netlist.h,v 1.47 1999/07/17 19:51:00 steve Exp $"
+#ident "$Id: netlist.h,v 1.48 1999/07/17 22:01:13 steve Exp $"
 #endif
 
 /*
@@ -44,6 +44,7 @@ class ostream;
 
 
 struct target;
+struct functor_t;
 
 /* =========
  * A NetObj is anything that has any kind of behavior in the
@@ -1278,6 +1279,7 @@ class Design {
 
 	// Iterate over the design...
       void dump(ostream&) const;
+      void functor(struct functor_t*);
       void emit(ostream&, struct target_t*) const;
 
       void clear_node_marks();
@@ -1366,6 +1368,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
 
 /*
  * $Log: netlist.h,v $
+ * Revision 1.48  1999/07/17 22:01:13  steve
+ *  Add the functor interface for functor transforms.
+ *
  * Revision 1.47  1999/07/17 19:51:00  steve
  *  netlist support for ternary operator.
  *
diff --git a/xnfio.cc b/xnfio.cc
index e76783485..71582563a 100644
--- a/xnfio.cc
+++ b/xnfio.cc
@@ -17,11 +17,20 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: xnfio.cc,v 1.1 1998/12/07 04:53:17 steve Exp $"
+#ident "$Id: xnfio.cc,v 1.2 1999/07/17 22:01:14 steve Exp $"
 #endif
 
+# include  "functor.h"
 # include  "netlist.h"
 
+class xnfio_f  : public functor_t {
+
+    public:
+      void signal(Design*des, NetNet*sig);
+
+    private:
+};
+
 static bool is_a_pad(const NetNet*net)
 {
       if (net->attribute("PAD") == "")
@@ -153,35 +162,42 @@ static void make_ibuf(Design*des, NetNet*net)
       }
 }
 
+void xnfio_f::signal(Design*des, NetNet*net)
+{
+      if (! is_a_pad(net))
+	    return;
+
+      assert(net->pin_count() == 1);
+      string pattr = net->attribute("PAD");
+
+      switch (pattr[0]) {
+	  case 'i':
+	  case 'I':
+	    make_ibuf(des, net);
+	    break;
+	  case 'o':
+	  case 'O':
+	    make_obuf(des, net);
+	    break;
+	      // FIXME: Only IPAD and OPAD supported. Need to
+	      // add support for IOPAD.
+	  default:
+	    assert(0);
+	    break;
+      }
+}
+
 void xnfio(Design*des)
 {
-      des->clear_signal_marks();
-      while (NetNet*net = des->find_signal(&is_a_pad)) {
-
-	    assert(net->pin_count() == 1);
-	    string pattr = net->attribute("PAD");
-
-	    switch (pattr[0]) {
-		case 'i':
-		case 'I':
-		  make_ibuf(des, net);
-		  break;
-		case 'o':
-		case 'O':
-		  make_obuf(des, net);
-		  break;
-		    // FIXME: Only IPAD and OPAD supported. Need to
-		    // add support for IOPAD.
-		default:
-		  assert(0);
-		  break;
-	    }
-	    net->set_mark();
-      }
+      xnfio_f xnfio_obj;
+      des->functor(&xnfio_obj);
 }
 
 /*
  * $Log: xnfio.cc,v $
+ * Revision 1.2  1999/07/17 22:01:14  steve
+ *  Add the functor interface for functor transforms.
+ *
  * Revision 1.1  1998/12/07 04:53:17  steve
  *  Generate OBUF or IBUF attributes (and the gates
  *  to garry them) where a wire is a pad. This involved