diff -r 35c2543f45fb -r f45703336699 src/include/invalid.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/include/invalid.h	Mon Mar 29 08:16:18 2004 +0000
@@ -0,0 +1,33 @@
+// -*- mode:C++ -*-
+
+#ifndef HUGO_INVALID_H
+#define HUGO_INVALID_H
+
+///\file
+///\brief Definition of INVALID.
+
+namespace hugo {
+
+  /// Dummy type to make it easier to make invalid iterators.
+  
+  /// See \ref INVALID, how to use it.
+  
+  struct Invalid {};
+  
+  /// Invalid iterators.
+  
+  /// \ref Invalid is a global type that converts to each iterator
+  /// in such a way that the value of the target iterator will be invalid.
+
+  // It is also used to convert the \c INVALID constant to the
+  // node iterator that makes is possible to write 
+
+  //extern Invalid INVALID;
+
+  //const Invalid &INVALID = *(Invalid *)0;
+  const Invalid INVALID = Invalid();
+
+};
+
+#endif
+