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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