new file mode 100644
--- /dev/null
+++ b/src/pt-base.cc
@@ -0,0 +1,84 @@
+// tree-base.cc                                           -*- C++ -*-
+/*
+
+Copyright (C) 1992, 1993, 1994 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 2, 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, write to the Free
+Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#if defined (__GNUG__)
+#pragma implementation
+#endif
+
+#include <iostream.h>
+#include <assert.h>
+
+#include "tree-base.h"
+
+// Current indentation.
+int tree_print_code::curr_print_indent_level = 0;
+
+// Nonzero means we are at the beginning of a line.
+int tree_print_code::beginning_of_line = 1;
+
+// All print_code() functions should use this to print new lines.
+
+void
+tree_print_code::print_code_new_line (ostream& os)
+{
+  os << "\n";
+
+  beginning_of_line = 1;
+}
+
+// Each print_code() function should call this before printing
+// anything.
+//
+// This doesn't need to be fast, but isn't there a better way?
+
+void
+tree_print_code::print_code_indent (ostream& os)
+{
+  assert (curr_print_indent_level >= 0);
+ 
+  if (beginning_of_line)
+    {
+      os.form ("%*s", curr_print_indent_level, "");
+      beginning_of_line = 0;
+    }
+}
+
+// For ressetting print_code state.
+
+void
+tree_print_code::print_code_reset (void)
+{
+  beginning_of_line = 1;
+  curr_print_indent_level = 0;
+}
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; page-delimiter: "^/\\*" ***
+;;; End: ***
+*/