diff -r d8863141824d -r fb261e3a9a0f src/hugo/invalid.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hugo/invalid.h	Thu May 06 13:21:24 2004 +0000
@@ -0,0 +1,38 @@
+// -*- 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 {
+  public:
+    bool operator==(Invalid) { return true;  }
+    bool operator!=(Invalid) { return false; }
+    bool operator< (Invalid) { return false; }
+  };
+  
+  /// 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();
+
+} //namespace hugo
+
+#endif
+