--- a/libinterp/parse-tree/module.mk	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/module.mk	Thu Apr 20 12:52:32 2017 -0400
@@ -81,6 +81,7 @@
   libinterp/parse-tree/pt-select.cc \
   libinterp/parse-tree/pt-stmt.cc \
   libinterp/parse-tree/pt-unop.cc \
+  libinterp/parse-tree/pt-walk.cc \
   libinterp/parse-tree/pt.cc \
   libinterp/parse-tree/token.cc
 

--- a/libinterp/parse-tree/pt-binop.cc	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/pt-binop.cc	Thu Apr 20 12:52:32 2017 -0400
@@ -255,4 +255,10 @@
 
     return new_be;
   }
+
+  void
+  tree_boolean_expression::accept (tree_walker& tw)
+  {
+    tw.visit_boolean_expression (*this);
+  }
 }

--- a/libinterp/parse-tree/pt-binop.h	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/pt-binop.h	Thu Apr 20 12:52:32 2017 -0400
@@ -176,6 +176,8 @@
     tree_expression *dup (symbol_table::scope_id scope,
                           symbol_table::context_id context) const;
 
+    void accept (tree_walker& tw);
+
   private:
 
     // The type of the expression.

--- a/libinterp/parse-tree/pt-cbinop.cc	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/pt-cbinop.cc	Thu Apr 20 12:52:32 2017 -0400
@@ -239,4 +239,10 @@
 
     return ret;
   }
+
+  void
+  tree_compound_binary_expression::accept (tree_walker& tw)
+  {
+    tw.visit_compound_binary_expression (*this);
+  }
 }

--- a/libinterp/parse-tree/pt-cbinop.h	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/pt-cbinop.h	Thu Apr 20 12:52:32 2017 -0400
@@ -61,6 +61,8 @@
 
     octave_value_list rvalue (int nargout);
 
+    void accept (tree_walker& tw);
+
   private:
 
     tree_expression *op_lhs;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libinterp/parse-tree/pt-walk.cc	Thu Apr 20 12:52:32 2017 -0400
@@ -0,0 +1,44 @@
+/*
+
+Copyright (C) 2017 John W. Eaton
+
+This file is part of Octave.
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3 of the License, or
+(at your option) any later version.
+
+Octave 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 Octave; see the file COPYING.  If not, see
+<http://www.gnu.org/licenses/>.
+
+*/
+
+#if defined (HAVE_CONFIG_H)
+#  include "config.h"
+#endif
+
+#include "pt-binop.h"
+#include "pt-cbinop.h"
+#include "pt-walk.h"
+
+namespace octave
+{
+  void
+  tree_walker::visit_boolean_expression (tree_boolean_expression& expr)
+  {
+    visit_binary_expression (expr);
+  }
+
+  void
+  tree_walker::visit_compound_binary_expression (tree_compound_binary_expression& expr)
+  {
+    visit_binary_expression (expr);
+  }
+}

--- a/libinterp/parse-tree/pt-walk.h	Thu Apr 20 12:27:35 2017 -0400
+++ b/libinterp/parse-tree/pt-walk.h	Thu Apr 20 12:52:32 2017 -0400
@@ -30,9 +30,18 @@
 
 namespace octave
 {
+  // No separate visitor needed
+  // Base classes only, so no need to include them.
+  //
+  //  class tree_array_list
+  //  class tree_unary_expression
+  //  class tree_black_hole
+
   class tree_anon_fcn_handle;
   class tree_argument_list;
   class tree_binary_expression;
+  class tree_boolean_expression;
+  class tree_compound_binary_expression;
   class tree_break_command;
   class tree_colon_expression;
   class tree_continue_command;
@@ -115,6 +124,12 @@
     visit_binary_expression (tree_binary_expression&) = 0;
 
     virtual void
+    visit_boolean_expression (tree_boolean_expression& expr);
+
+    virtual void
+    visit_compound_binary_expression (tree_compound_binary_expression& expr);
+
+    virtual void
     visit_break_command (tree_break_command&) = 0;
 
     virtual void