1 | /* -*- C++ -*- |
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2 | * |
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3 | * src/lemon/utility.h - Part of LEMON, a generic C++ optimization library |
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4 | * |
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5 | * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi |
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6 | * Kutatocsoport (Egervary Research Group on Combinatorial Optimization, |
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7 | * 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 | * This file contains a modified version of the enable_if library from BOOST. |
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18 | * See the appropriate copyright notice below. |
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19 | */ |
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20 | |
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21 | // Boost enable_if library |
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22 | |
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23 | // Copyright 2003 © The Trustees of Indiana University. |
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24 | |
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25 | // Use, modification, and distribution is subject to the Boost Software |
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26 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
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27 | // http://www.boost.org/LICENSE_1_0.txt) |
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28 | |
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29 | // Authors: Jaakko Järvi (jajarvi at osl.iu.edu) |
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30 | // Jeremiah Willcock (jewillco at osl.iu.edu) |
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31 | // Andrew Lumsdaine (lums at osl.iu.edu) |
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32 | |
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33 | |
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34 | #ifndef LEMON_UTILITY_H |
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35 | #define LEMON_UTILITY_H |
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36 | |
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37 | namespace lemon |
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38 | { |
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39 | |
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40 | /// Basic type for defining "tags". A "YES" condition for enable_if. |
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41 | |
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42 | /// \todo This should go to a separate "basic_types.h" (or something) |
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43 | /// file. |
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44 | struct True { |
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45 | static const bool value = true; |
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46 | }; |
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47 | |
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48 | /// Basic type for defining "tags". A "NO" condition for enable_if. |
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49 | struct False { |
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50 | static const bool value = false; |
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51 | }; |
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52 | |
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53 | template <typename T> |
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54 | struct Wrap { |
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55 | const T &value; |
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56 | Wrap(const T &t) : value(t) {} |
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57 | }; |
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58 | |
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59 | /**************** dummy class to avoid ambiguity ****************/ |
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60 | |
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61 | template<int T> struct dummy { dummy(int) {} }; |
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62 | |
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63 | /**************** enable_if from BOOST ****************/ |
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64 | |
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65 | template <bool B, class T = void> |
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66 | struct enable_if_c { |
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67 | typedef T type; |
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68 | }; |
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69 | |
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70 | template <class T> |
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71 | struct enable_if_c<false, T> {}; |
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72 | |
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73 | template <class Cond, class T = void> |
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74 | struct enable_if : public enable_if_c<Cond::value, T> {}; |
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75 | |
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76 | template <bool B, class T> |
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77 | struct lazy_enable_if_c { |
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78 | typedef typename T::type type; |
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79 | }; |
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80 | |
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81 | template <class T> |
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82 | struct lazy_enable_if_c<false, T> {}; |
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83 | |
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84 | template <class Cond, class T> |
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85 | struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {}; |
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86 | |
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87 | |
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88 | template <bool B, class T = void> |
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89 | struct disable_if_c { |
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90 | typedef T type; |
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91 | }; |
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92 | |
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93 | template <class T> |
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94 | struct disable_if_c<true, T> {}; |
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95 | |
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96 | template <class Cond, class T = void> |
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97 | struct disable_if : public disable_if_c<Cond::value, T> {}; |
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98 | |
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99 | template <bool B, class T> |
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100 | struct lazy_disable_if_c { |
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101 | typedef typename T::type type; |
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102 | }; |
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103 | |
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104 | template <class T> |
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105 | struct lazy_disable_if_c<true, T> {}; |
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106 | |
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107 | template <class Cond, class T> |
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108 | struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {}; |
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109 | |
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110 | // smart referencing |
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111 | |
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112 | template <typename _Type, typename Enable = void> |
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113 | struct SmartReference { |
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114 | typedef _Type& Type; |
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115 | }; |
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116 | |
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117 | template <typename _Type> |
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118 | struct SmartReference< |
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119 | _Type, |
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120 | typename enable_if<typename _Type::NeedCopy, void>::type |
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121 | > { |
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122 | typedef _Type Type; |
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123 | }; |
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124 | |
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125 | template <typename _Type, typename Enable = void> |
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126 | struct SmartConstReference { |
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127 | typedef const _Type& Type; |
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128 | }; |
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129 | |
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130 | template <typename _Type> |
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131 | struct SmartConstReference< |
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132 | _Type, |
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133 | typename enable_if<typename _Type::NeedCopy, void>::type |
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134 | > { |
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135 | typedef const _Type Type; |
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136 | }; |
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137 | |
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138 | template <typename _Type, typename Enable = void> |
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139 | struct SmartParameter { |
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140 | typedef _Type& Type; |
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141 | }; |
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142 | |
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143 | template <typename _Type> |
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144 | struct SmartParameter< |
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145 | _Type, |
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146 | typename enable_if<typename _Type::NeedCopy, void>::type |
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147 | > { |
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148 | typedef const _Type& Type; |
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149 | }; |
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150 | |
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151 | } // namespace lemon |
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152 | |
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153 | #endif |
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