--- a/src/pt-const.cc
+++ b/src/pt-const.cc
@@ -30,6 +30,7 @@
 
 #include <iostream.h>
 
+#include "error.h"
 #include "oct-obj.h"
 #include "pager.h"
 #include "pt-const.h"
@@ -59,19 +60,17 @@
     val.print_raw (os, pr_as_read_syntax);
 }
 
-octave_value
-tree_constant::eval (bool print_result)
+octave_value_list
+tree_constant::rvalue (int nargout)
 {
-  if (print_result)
-    val.print (octave_stdout);
+  octave_value_list retval;
 
-  return val;
-}
+  if (nargout > 1)
+    error ("invalid number of output arguments for constant expression");
+  else
+    retval = rvalue ();
 
-octave_value_list
-tree_constant::eval (bool, int, const octave_value_list& idx)
-{
-  return (idx.length () > 0) ? val.do_index_op (idx) : val;
+  return retval;
 }
 
 void