diff -r 6e1b62d42d94 -r 2115143eceea lemon/bits/invalid.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lemon/bits/invalid.h	Wed Mar 01 13:19:28 2006 +0000
@@ -0,0 +1,54 @@
+/* -*- C++ -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2003-2006
+ * 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_BITS_INVALID_H
+#define LEMON_BITS_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.
+
+  //const Invalid &INVALID = *(Invalid *)0;
+
+#ifdef LEMON_ONLY_TEMPLATES
+  const Invalid INVALID = Invalid();
+#else
+  extern const Invalid INVALID;
+#endif
+
+} //namespace lemon
+
+#endif
+