new file mode 100644
--- /dev/null
+++ b/src/pt-colon.cc
@@ -0,0 +1,184 @@
+/*
+
+Copyright (C) 1996, 1997 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, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+
+*/
+
+#if defined (__GNUG__)
+#pragma implementation
+#endif
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "error.h"
+#include "oct-obj.h"
+#include "pager.h"
+#include "ov.h"
+#include "pt-colon.h"
+#include "pt-pr-code.h"
+#include "pt-walk.h"
+
+// Colon expressions.
+
+tree_colon_expression *
+tree_colon_expression::append (tree_expression *t)
+{
+  tree_colon_expression *retval = 0;
+
+  if (op_base)
+    {
+      if (op_limit)
+	{
+	  if (op_increment)
+	    ::error ("invalid colon expression");
+	  else
+	    {
+	      // Stupid syntax:
+	      //
+	      // base : limit
+	      // base : increment : limit
+
+	      op_increment = op_limit;
+	      op_limit = t;
+	    }
+	}
+      else
+	op_limit = t;
+
+      retval = this;
+    }
+  else
+    ::error ("invalid colon expression");
+
+  return retval;
+}
+
+octave_value_list
+tree_colon_expression::rvalue (int nargout)
+{
+  octave_value_list retval;
+
+  if (nargout > 1)
+    error ("invalid number of output arguments for colon expression");
+  else
+    retval = rvalue ();
+
+  return retval;
+}
+
+octave_value
+tree_colon_expression::rvalue (void)
+{
+  octave_value retval;
+
+  if (error_state || ! op_base || ! op_limit)
+    return retval;
+
+  octave_value tmp = op_base->rvalue ();
+
+  if (tmp.is_undefined ())
+    {
+      eval_error ("invalid null value in colon expression");
+      return retval;
+    }
+
+  double xbase = tmp.double_value ();
+
+  if (error_state)
+    {
+      eval_error ("colon expression elements must be scalars");
+      return retval;
+    }
+
+  tmp = op_limit->rvalue ();
+
+  if (tmp.is_undefined ())
+    {
+      eval_error ("invalid null value in colon expression");
+      return retval;
+    }
+
+  double xlimit = tmp.double_value ();
+
+  if (error_state)
+    {
+      eval_error ("colon expression elements must be scalars");
+      return retval;
+    }
+
+  double xinc = 1.0;
+
+  if (op_increment)
+    {
+      tmp = op_increment->rvalue ();
+
+      if (tmp.is_undefined ())
+	{
+	  eval_error ("invalid null value in colon expression");
+	  return retval;
+	}
+
+      xinc = tmp.double_value ();
+
+      if (error_state)
+	{
+	  eval_error ("colon expression elements must be scalars");
+	  return retval;
+	}
+    }
+
+  retval = octave_value (xbase, xlimit, xinc);
+
+  if (error_state)
+    {
+      if (error_state)
+	eval_error ();
+
+      return octave_value ();
+    }
+
+  return retval;
+}
+
+void
+tree_colon_expression::eval_error (const string& s)
+{
+  if (error_state > 0)
+    {
+      if (! s.empty ())
+	::error ("%s", s.c_str ());
+
+      ::error ("evaluating colon expression near line %d column %d",
+	       line (), column ());
+    }
+}
+
+void
+tree_colon_expression::accept (tree_walker& tw)
+{
+  tw.visit_colon_expression (*this);
+}
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; End: ***
+*/