1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/lemon/bits/invalid.h	Thu Dec 20 15:59:06 2007 +0000
     1.3 @@ -0,0 +1,54 @@
     1.4 +/* -*- C++ -*-
     1.5 + *
     1.6 + * This file is a part of LEMON, a generic C++ optimization library
     1.7 + *
     1.8 + * Copyright (C) 2003-2007
     1.9 + * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
    1.10 + * (Egervary Research Group on Combinatorial Optimization, EGRES).
    1.11 + *
    1.12 + * Permission to use, modify and distribute this software is granted
    1.13 + * provided that this copyright notice appears in all copies. For
    1.14 + * precise terms see the accompanying LICENSE file.
    1.15 + *
    1.16 + * This software is provided "AS IS" with no warranty of any kind,
    1.17 + * express or implied, and with no claim as to its suitability for any
    1.18 + * purpose.
    1.19 + *
    1.20 + */
    1.21 +
    1.22 +#ifndef LEMON_BITS_INVALID_H
    1.23 +#define LEMON_BITS_INVALID_H
    1.24 +
    1.25 +///\file
    1.26 +///\brief Definition of INVALID.
    1.27 +
    1.28 +namespace lemon {
    1.29 +
    1.30 +  /// \brief Dummy type to make it easier to make invalid iterators.
    1.31 +  ///
    1.32 +  /// See \ref INVALID for the usage.
    1.33 +  struct Invalid {
    1.34 +  public:
    1.35 +    bool operator==(Invalid) { return true;  }
    1.36 +    bool operator!=(Invalid) { return false; }
    1.37 +    bool operator< (Invalid) { return false; }
    1.38 +  };
    1.39 +  
    1.40 +  /// Invalid iterators.
    1.41 +  
    1.42 +  /// \ref Invalid is a global type that converts to each iterator
    1.43 +  /// in such a way that the value of the target iterator will be invalid.
    1.44 +
    1.45 +  //Some people didn't like this:
    1.46 +  //const Invalid &INVALID = *(Invalid *)0;
    1.47 +
    1.48 +#ifdef LEMON_ONLY_TEMPLATES
    1.49 +  const Invalid INVALID = Invalid();
    1.50 +#else
    1.51 +  extern const Invalid INVALID;
    1.52 +#endif
    1.53 +
    1.54 +} //namespace lemon
    1.55 +
    1.56 +#endif
    1.57 +