diff -r d8475431bbbb -r 8e85e6bbefdf lemon/invalid.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lemon/invalid.h	Mon May 23 04:48:14 2005 +0000
@@ -0,0 +1,52 @@
+/* -*- C++ -*-
+ * lemon/invalid.h - Part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+#ifndef LEMON_INVALID_H
+#define LEMON_INVALID_H
+
+///\file
+///\brief Definition of INVALID.
+
+namespace lemon {
+
+  /// 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 lemon
+
+#endif
+