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