diff --git a/design_dump.cc b/design_dump.cc
index f4b6e3699..0932eadcf 100644
--- a/design_dump.cc
+++ b/design_dump.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: design_dump.cc,v 1.17 1999/04/19 01:59:36 steve Exp $"
+#ident "$Id: design_dump.cc,v 1.18 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 /*
@@ -469,6 +469,14 @@ void NetESignal::dump(ostream&o) const
       o << name();
 }
 
+void NetESubSignal::dump(ostream&o) const
+{
+      sig_->dump(o);
+      o << "[";
+      idx_->dump(o);
+      o << "]";
+}
+
 void NetEMemory::dump(ostream&o) const
 {
       o << mem_->name() << "[";
@@ -543,6 +551,9 @@ void Design::dump(ostream&o) const
 
 /*
  * $Log: design_dump.cc,v $
+ * Revision 1.18  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.17  1999/04/19 01:59:36  steve
  *  Add memories to the parse and elaboration phases.
  *
diff --git a/elaborate.cc b/elaborate.cc
index 0a6b63531..73cf4787e 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: elaborate.cc,v 1.19 1999/04/19 01:59:36 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.20 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 /*
@@ -680,41 +680,56 @@ NetExpr* PEString::elaborate_expr(Design*des, const string&path) const
 
 NetExpr*PEIdent::elaborate_expr(Design*des, const string&path) const
 {
-      if (text_[0] == '$') {
+	// System identifiers show up in the netlist as identifiers.
+      if (text_[0] == '$')
 	    return new NetEIdent(text_, 64);
 
-      } else {
-	    string name = path+"."+text_;
+      string name = path+"."+text_;
 
-	    if (NetExpr*ex = des->get_parameter(name))
-		  return ex;
+	// If the identifier name a paramter name, then return
+	// the expression that it represents.
+      if (NetExpr*ex = des->get_parameter(name))
+	    return ex;
 
-	    if (NetNet*net = des->find_signal(name)) {
-		  NetESignal*node = des->get_esignal(net);
-		  return node;
+	// If the identifier names a signal (a register or wire)
+	// then create a NetESignal node to handle it.
+      if (NetNet*net = des->find_signal(name)) {
+	    NetESignal*node = des->get_esignal(net);
+	    assert(idx_ == 0);
+	    assert(lsb_ == 0);
+	    if (msb_) {
+		  NetExpr*ex = msb_->elaborate_expr(des, path);
+		  NetESubSignal*ss = new NetESubSignal(node, ex);
+		  return ss;
 	    }
-
-	    if (NetMemory*mem = des->find_memory(name)) {
-		  assert(msb_ != 0);
-		  assert(lsb_ == 0);
-		  assert(idx_ == 0);
-		  NetExpr*i = msb_->elaborate_expr(des, path);
-		  if (i == 0) {
-			cerr << get_line() << ": Unable to exaborate "
-			      "index expression `" << *msb_ << "'" << endl;
-			des->errors += 1;
-			return 0;
-		  }
-
-		  NetEMemory*node = new NetEMemory(mem, i);
-		  return node;
-	    }
-
-	    cerr << get_line() << ": Unable to bind wire/reg/memory "
-		  "`" << path << "." << text_ << "'" << endl;
-	    des->errors += 1;
-	    return 0;
+	    assert(msb_ == 0);
+	    return node;
       }
+
+	// If the identifier names a memory, then this is a
+	// memory reference and I must generate a NetEMemory
+	// object to handle it.
+      if (NetMemory*mem = des->find_memory(name)) {
+	    assert(msb_ != 0);
+	    assert(lsb_ == 0);
+	    assert(idx_ == 0);
+	    NetExpr*i = msb_->elaborate_expr(des, path);
+	    if (i == 0) {
+		  cerr << get_line() << ": Unable to exaborate "
+			"index expression `" << *msb_ << "'" << endl;
+		  des->errors += 1;
+		  return 0;
+	    }
+
+	    NetEMemory*node = new NetEMemory(mem, i);
+	    return node;
+      }
+
+	// I cannot interpret this identifier. Error message.
+      cerr << get_line() << ": Unable to bind wire/reg/memory "
+	    "`" << path << "." << text_ << "'" << endl;
+      des->errors += 1;
+      return 0;
 }
 
 NetExpr* PExpr::elaborate_expr(Design*des, const string&path) const
@@ -1028,6 +1043,9 @@ Design* elaborate(const map<string,Module*>&modules,
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.20  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.19  1999/04/19 01:59:36  steve
  *  Add memories to the parse and elaboration phases.
  *
diff --git a/emit.cc b/emit.cc
index 2f0fba8d2..9fdfe33a3 100644
--- a/emit.cc
+++ b/emit.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: emit.cc,v 1.7 1999/04/19 01:59:36 steve Exp $"
+#ident "$Id: emit.cc,v 1.8 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 /*
@@ -229,6 +229,11 @@ void NetESignal::emit_node(ostream&o, struct target_t*tgt) const
       tgt->net_esignal(o, this);
 }
 
+void NetESubSignal::expr_scan(struct expr_scan_t*tgt) const
+{
+      tgt->expr_subsignal(this);
+}
+
 void NetEUnary::expr_scan(struct expr_scan_t*tgt) const
 {
       tgt->expr_unary(this);
@@ -248,6 +253,9 @@ void emit(ostream&o, const Design*des, const char*type)
 
 /*
  * $Log: emit.cc,v $
+ * Revision 1.8  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.7  1999/04/19 01:59:36  steve
  *  Add memories to the parse and elaboration phases.
  *
diff --git a/netlist.cc b/netlist.cc
index 126fe1c80..37dce1348 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: netlist.cc,v 1.20 1999/04/19 01:59:36 steve Exp $"
+#ident "$Id: netlist.cc,v 1.21 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 # include  <cassert>
@@ -536,6 +536,16 @@ void NetESignal::set_width(unsigned w)
       expr_width(w);
 }
 
+NetESubSignal::NetESubSignal(NetESignal*sig, NetExpr*ex)
+: sig_(sig), idx_(ex)
+{
+}
+
+NetESubSignal::~NetESubSignal()
+{
+      idx_.clr_and_delete();
+}
+
 NetEUnary::~NetEUnary()
 {
       expr_.clr_and_delete();
@@ -1016,6 +1026,9 @@ NetNet* Design::find_signal(bool (*func)(const NetNet*))
 
 /*
  * $Log: netlist.cc,v $
+ * Revision 1.21  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.20  1999/04/19 01:59:36  steve
  *  Add memories to the parse and elaboration phases.
  *
diff --git a/netlist.h b/netlist.h
index d829584f5..204e880f1 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 1.24 1999/04/22 04:56:58 steve Exp $"
+#ident "$Id: netlist.h,v 1.25 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 /*
@@ -972,6 +972,29 @@ class NetESignal  : public NetExpr, public NetNode {
     private:
 };
 
+/*
+ * An expression that takes a portion of a signal is represented as
+ * one of these. For example, ``foo[x+5]'' is a signal and x+5 is an
+ * expression to select a single bit from that signal. I can't just
+ * make a new NetESignal node connected to the single net because the
+ * expression may vary during execution, so the structure is not known
+ * at compile (elaboration) time.
+ */
+class NetESubSignal  : public NetExpr {
+
+    public:
+      NetESubSignal(NetESignal*sig, NetExpr*ex);
+      ~NetESubSignal();
+
+      virtual void expr_scan(struct expr_scan_t*) const;
+      virtual void dump(ostream&) const;
+
+    private:
+	// For now, only support single-bit selects of a signal.
+      NetESignal*sig_;
+      NetExpr::REF idx_;
+};
+
 /*
  * This class contains an entire design. It includes processes and a
  * netlist, and can be passed around from function to function.
@@ -1103,6 +1126,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
 
 /*
  * $Log: netlist.h,v $
+ * Revision 1.25  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.24  1999/04/22 04:56:58  steve
  *  Add to vvm proceedural memory references.
  *
diff --git a/target.cc b/target.cc
index b3bc98174..57caa252e 100644
--- a/target.cc
+++ b/target.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: target.cc,v 1.6 1999/04/19 01:59:37 steve Exp $"
+#ident "$Id: target.cc,v 1.7 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 # include  "target.h"
@@ -164,6 +164,12 @@ void expr_scan_t::expr_signal(const NetESignal*)
 	    "unhandled expr_signal." << endl;
 }
 
+void expr_scan_t::expr_subsignal(const NetESubSignal*)
+{
+      cerr << "expr_scan_t (" << typeid(*this).name() << "): "
+	    "unhandled expr_subsignal." << endl;
+}
+
 void expr_scan_t::expr_unary(const NetEUnary*)
 {
       cerr << "expr_scan_t (" << typeid(*this).name() << "): "
@@ -178,6 +184,9 @@ void expr_scan_t::expr_binary(const NetEBinary*ex)
 
 /*
  * $Log: target.cc,v $
+ * Revision 1.7  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.6  1999/04/19 01:59:37  steve
  *  Add memories to the parse and elaboration phases.
  *
diff --git a/target.h b/target.h
index 0a2d9f9cf..cc92c1411 100644
--- a/target.h
+++ b/target.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: target.h,v 1.6 1999/04/19 01:59:37 steve Exp $"
+#ident "$Id: target.h,v 1.7 1999/04/25 00:44:10 steve Exp $"
 #endif
 
 # include  "netlist.h"
@@ -99,6 +99,7 @@ struct expr_scan_t {
       virtual void expr_ident(const NetEIdent*);
       virtual void expr_memory(const NetEMemory*);
       virtual void expr_signal(const NetESignal*);
+      virtual void expr_subsignal(const NetESubSignal*);
       virtual void expr_unary(const NetEUnary*);
       virtual void expr_binary(const NetEBinary*);
 };
@@ -120,6 +121,9 @@ extern const struct target *target_table[];
 
 /*
  * $Log: target.h,v $
+ * Revision 1.7  1999/04/25 00:44:10  steve
+ *  Core handles subsignal expressions.
+ *
  * Revision 1.6  1999/04/19 01:59:37  steve
  *  Add memories to the parse and elaboration phases.
  *