1 | /* -*- C++ -*- |
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2 | * lemon/utility.h - Part of LEMON, a generic C++ optimization library |
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3 | * |
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4 | * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi |
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5 | * Kutatocsoport (Egervary Research Group on Combinatorial Optimization, |
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6 | * EGRES). |
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7 | * |
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8 | * Permission to use, modify and distribute this software is granted |
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9 | * provided that this copyright notice appears in all copies. For |
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10 | * precise terms see the accompanying LICENSE file. |
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11 | * |
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12 | * This software is provided "AS IS" with no warranty of any kind, |
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13 | * express or implied, and with no claim as to its suitability for any |
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14 | * purpose. |
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15 | * |
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16 | * This file contains a modified version of the enable_if library from BOOST. |
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17 | * See the appropriate copyright notice below. |
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18 | */ |
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19 | |
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20 | // Boost enable_if library |
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21 | |
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22 | // Copyright 2003 © The Trustees of Indiana University. |
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23 | |
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24 | // Use, modification, and distribution is subject to the Boost Software |
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25 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
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26 | // http://www.boost.org/LICENSE_1_0.txt) |
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27 | |
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28 | // Authors: Jaakko Järvi (jajarvi at osl.iu.edu) |
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29 | // Jeremiah Willcock (jewillco at osl.iu.edu) |
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30 | // Andrew Lumsdaine (lums at osl.iu.edu) |
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31 | |
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32 | |
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33 | #ifndef LEMON_UTILITY_H |
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34 | #define LEMON_UTILITY_H |
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35 | |
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36 | namespace lemon |
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37 | { |
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38 | |
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39 | /// Basic type for defining "tags". A "YES" condition for enable_if. |
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40 | |
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41 | /// \todo This should go to a separate "basic_types.h" (or something) |
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42 | /// file. |
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43 | struct True { |
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44 | static const bool value = true; |
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45 | }; |
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46 | |
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47 | /// Basic type for defining "tags". A "NO" condition for enable_if. |
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48 | struct False { |
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49 | static const bool value = false; |
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50 | }; |
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51 | |
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52 | template <typename T> |
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53 | struct Wrap { |
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54 | const T &value; |
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55 | Wrap(const T &t) : value(t) {} |
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56 | }; |
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57 | |
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58 | /**************** dummy class to avoid ambiguity ****************/ |
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59 | |
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60 | template<int T> struct dummy { dummy(int) {} }; |
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61 | |
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62 | /**************** enable_if from BOOST ****************/ |
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63 | |
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64 | template <bool B, class T = void> |
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65 | struct enable_if_c { |
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66 | typedef T type; |
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67 | }; |
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68 | |
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69 | template <class T> |
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70 | struct enable_if_c<false, T> {}; |
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71 | |
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72 | template <class Cond, class T = void> |
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73 | struct enable_if : public enable_if_c<Cond::value, T> {}; |
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74 | |
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75 | template <bool B, class T> |
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76 | struct lazy_enable_if_c { |
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77 | typedef typename T::type type; |
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78 | }; |
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79 | |
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80 | template <class T> |
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81 | struct lazy_enable_if_c<false, T> {}; |
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82 | |
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83 | template <class Cond, class T> |
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84 | struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {}; |
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85 | |
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86 | |
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87 | template <bool B, class T = void> |
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88 | struct disable_if_c { |
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89 | typedef T type; |
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90 | }; |
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91 | |
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92 | template <class T> |
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93 | struct disable_if_c<true, T> {}; |
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94 | |
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95 | template <class Cond, class T = void> |
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96 | struct disable_if : public disable_if_c<Cond::value, T> {}; |
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97 | |
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98 | template <bool B, class T> |
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99 | struct lazy_disable_if_c { |
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100 | typedef typename T::type type; |
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101 | }; |
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102 | |
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103 | template <class T> |
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104 | struct lazy_disable_if_c<true, T> {}; |
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105 | |
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106 | template <class Cond, class T> |
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107 | struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {}; |
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108 | |
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109 | // smart referencing |
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110 | |
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111 | template <typename _Type, typename Enable = void> |
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112 | struct SmartReference { |
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113 | typedef _Type& Type; |
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114 | }; |
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115 | |
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116 | template <typename _Type> |
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117 | struct SmartReference< |
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118 | _Type, |
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119 | typename enable_if<typename _Type::NeedCopy, void>::type |
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120 | > { |
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121 | typedef _Type Type; |
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122 | }; |
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123 | |
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124 | template <typename _Type, typename Enable = void> |
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125 | struct SmartConstReference { |
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126 | typedef const _Type& Type; |
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127 | }; |
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128 | |
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129 | template <typename _Type> |
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130 | struct SmartConstReference< |
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131 | _Type, |
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132 | typename enable_if<typename _Type::NeedCopy, void>::type |
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133 | > { |
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134 | typedef const _Type Type; |
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135 | }; |
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136 | |
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137 | template <typename _Type, typename Enable = void> |
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138 | struct SmartParameter { |
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139 | typedef _Type& Type; |
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140 | }; |
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141 | |
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142 | template <typename _Type> |
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143 | struct SmartParameter< |
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144 | _Type, |
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145 | typename enable_if<typename _Type::NeedCopy, void>::type |
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146 | > { |
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147 | typedef const _Type& Type; |
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148 | }; |
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149 | |
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150 | } // namespace lemon |
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151 | |
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152 | #endif |
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