alpar@2655: /* -*- C++ -*-
alpar@2655:  *
alpar@2655:  * This file is a part of LEMON, a generic C++ optimization library
alpar@2655:  *
alpar@2655:  * Copyright (C) 2003-2006
alpar@2655:  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@2655:  * (Egervary Research Group on Combinatorial Optimization, EGRES).
alpar@2655:  *
alpar@2655:  * Permission to use, modify and distribute this software is granted
alpar@2655:  * provided that this copyright notice appears in all copies. For
alpar@2655:  * precise terms see the accompanying LICENSE file.
alpar@2655:  *
alpar@2655:  * This software is provided "AS IS" with no warranty of any kind,
alpar@2655:  * express or implied, and with no claim as to its suitability for any
alpar@2655:  * purpose.
alpar@2655:  *
alpar@2655:  */
alpar@2655: 
alpar@2655: #ifndef LEMON_BITS_INVALID_H
alpar@2655: #define LEMON_BITS_INVALID_H
alpar@2655: 
alpar@2655: ///\file
alpar@2655: ///\brief Definition of INVALID.
alpar@2655: 
alpar@2655: namespace lemon {
alpar@2655: 
alpar@2655:   /// \brief Dummy type to make it easier to make invalid iterators.
alpar@2655:   ///
alpar@2655:   /// See \ref INVALID for the usage.
alpar@2655:   struct Invalid {
alpar@2655:   public:
alpar@2655:     bool operator==(Invalid) { return true;  }
alpar@2655:     bool operator!=(Invalid) { return false; }
alpar@2655:     bool operator< (Invalid) { return false; }
alpar@2655:   };
alpar@2655:   
alpar@2655:   /// Invalid iterators.
alpar@2655:   
alpar@2655:   /// \ref Invalid is a global type that converts to each iterator
alpar@2655:   /// in such a way that the value of the target iterator will be invalid.
alpar@2655: 
alpar@2655:   //Some people didn't like this:
alpar@2655:   //const Invalid &INVALID = *(Invalid *)0;
alpar@2655: 
alpar@2655: #ifdef LEMON_ONLY_TEMPLATES
alpar@2655:   const Invalid INVALID = Invalid();
alpar@2655: #else
alpar@2655:   extern const Invalid INVALID;
alpar@2655: #endif
alpar@2655: 
alpar@2655: } //namespace lemon
alpar@2655: 
alpar@2655: #endif
alpar@2655: