lemon/bits/invalid.h
changeset 17 d0dd44af6fec
child 13 83c84df7a956
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     1 /* -*- C++ -*-
       
     2  *
       
     3  * This file is a part of LEMON, a generic C++ optimization library
       
     4  *
       
     5  * Copyright (C) 2003-2007
       
     6  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
       
     7  * (Egervary Research Group on Combinatorial Optimization, EGRES).
       
     8  *
       
     9  * Permission to use, modify and distribute this software is granted
       
    10  * provided that this copyright notice appears in all copies. For
       
    11  * precise terms see the accompanying LICENSE file.
       
    12  *
       
    13  * This software is provided "AS IS" with no warranty of any kind,
       
    14  * express or implied, and with no claim as to its suitability for any
       
    15  * purpose.
       
    16  *
       
    17  */
       
    18 
       
    19 #ifndef LEMON_BITS_INVALID_H
       
    20 #define LEMON_BITS_INVALID_H
       
    21 
       
    22 ///\file
       
    23 ///\brief Definition of INVALID.
       
    24 
       
    25 namespace lemon {
       
    26 
       
    27   /// \brief Dummy type to make it easier to make invalid iterators.
       
    28   ///
       
    29   /// See \ref INVALID for the usage.
       
    30   struct Invalid {
       
    31   public:
       
    32     bool operator==(Invalid) { return true;  }
       
    33     bool operator!=(Invalid) { return false; }
       
    34     bool operator< (Invalid) { return false; }
       
    35   };
       
    36   
       
    37   /// Invalid iterators.
       
    38   
       
    39   /// \ref Invalid is a global type that converts to each iterator
       
    40   /// in such a way that the value of the target iterator will be invalid.
       
    41 
       
    42   //Some people didn't like this:
       
    43   //const Invalid &INVALID = *(Invalid *)0;
       
    44 
       
    45 #ifdef LEMON_ONLY_TEMPLATES
       
    46   const Invalid INVALID = Invalid();
       
    47 #else
       
    48   extern const Invalid INVALID;
       
    49 #endif
       
    50 
       
    51 } //namespace lemon
       
    52 
       
    53 #endif
       
    54