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1 //----------------------------------------------------------------------------- |
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2 // boost variant/recursive_variant.hpp header file |
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3 // See http://www.boost.org for updates, documentation, and revision history. |
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4 //----------------------------------------------------------------------------- |
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5 // |
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6 // Copyright (c) 2003 |
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7 // Eric Friedman |
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8 // |
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9 // Distributed under the Boost Software License, Version 1.0. (See |
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10 // accompanying file LICENSE_1_0.txt or copy at |
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11 // http://www.boost.org/LICENSE_1_0.txt) |
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12 |
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13 #ifndef BOOST_VARIANT_RECURSIVE_VARIANT_HPP |
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14 #define BOOST_VARIANT_RECURSIVE_VARIANT_HPP |
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15 |
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16 #include "boost/variant/variant_fwd.hpp" |
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17 #include "boost/variant/detail/enable_recursive.hpp" |
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18 #include "boost/variant/detail/substitute_fwd.hpp" |
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19 #include "boost/variant/detail/make_variant_list.hpp" |
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20 #include "boost/variant/detail/over_sequence.hpp" |
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21 |
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22 #include "boost/mpl/aux_/lambda_arity_param.hpp" |
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23 |
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24 #if !defined(BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT) |
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25 # include "boost/mpl/eval_if.hpp" |
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26 # include "boost/mpl/identity.hpp" |
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27 # include "boost/mpl/protect.hpp" |
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28 # include "boost/mpl/transform.hpp" |
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29 #else |
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30 # include "boost/preprocessor/cat.hpp" |
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31 # include "boost/preprocessor/repeat.hpp" |
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32 #endif |
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33 |
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34 #include "boost/mpl/bool.hpp" |
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35 #include "boost/mpl/is_sequence.hpp" |
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36 #include "boost/variant/variant.hpp" |
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37 |
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38 namespace boost { |
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39 |
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40 namespace detail { namespace variant { |
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41 |
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42 /////////////////////////////////////////////////////////////////////////////// |
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43 // (detail) metafunction specialization substitute |
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44 // |
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45 // Handles embedded variant types when substituting for recursive_variant_. |
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46 // |
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47 |
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48 #if !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) |
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49 |
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50 template < |
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51 BOOST_VARIANT_ENUM_PARAMS(typename T) |
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52 , typename RecursiveVariant |
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53 BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(typename Arity) |
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54 > |
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55 struct substitute< |
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56 ::boost::variant< |
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57 recursive_flag< T0 > |
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58 , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) |
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59 > |
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60 , RecursiveVariant |
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61 , ::boost::recursive_variant_ |
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62 BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(Arity) |
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63 > |
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64 { |
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65 typedef ::boost::variant< |
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66 recursive_flag< T0 > |
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67 , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) |
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68 > type; |
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69 }; |
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70 |
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71 template < |
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72 BOOST_VARIANT_ENUM_PARAMS(typename T) |
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73 , typename RecursiveVariant |
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74 BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(typename Arity) |
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75 > |
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76 struct substitute< |
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77 ::boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) > |
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78 , RecursiveVariant |
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79 , ::boost::recursive_variant_ |
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80 BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(Arity) |
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81 > |
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82 { |
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83 |
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84 #if !defined(BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT) |
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85 |
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86 private: // helpers, for metafunction result (below) |
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87 |
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88 typedef typename mpl::eval_if< |
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89 ::boost::detail::variant::is_over_sequence<T0> |
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90 , mpl::identity< T0 > |
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91 , make_variant_list< BOOST_VARIANT_ENUM_PARAMS(T) > |
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92 >::type initial_types; |
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93 |
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94 typedef typename mpl::transform< |
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95 initial_types |
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96 , mpl::protect< quoted_enable_recursive<RecursiveVariant,mpl::true_> > |
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97 >::type types; |
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98 |
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99 public: // metafunction result |
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100 |
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101 typedef ::boost::variant< types > type; |
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102 |
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103 #else // defined(BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT) |
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104 |
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105 private: // helpers, for metafunction result (below) |
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106 |
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107 #define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS(z,N,_) \ |
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108 typedef typename enable_recursive< \ |
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109 BOOST_PP_CAT(T,N) \ |
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110 , RecursiveVariant \ |
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111 , mpl::true_ \ |
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112 >::type BOOST_PP_CAT(wknd_T,N); \ |
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113 /**/ |
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114 |
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115 BOOST_PP_REPEAT( |
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116 BOOST_VARIANT_LIMIT_TYPES |
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117 , BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS |
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118 , _ |
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119 ) |
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120 |
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121 #undef BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS |
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122 |
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123 public: // metafunction result |
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124 |
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125 typedef ::boost::variant< BOOST_VARIANT_ENUM_PARAMS(wknd_T) > type; |
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126 |
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127 #endif // BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT workaround |
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128 |
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129 }; |
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130 |
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131 #else // defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) |
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132 |
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133 // |
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134 // no specializations: embedded variants unsupported on these compilers! |
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135 // |
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136 |
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137 #endif // !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) |
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138 |
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139 }} // namespace detail::variant |
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140 |
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141 /////////////////////////////////////////////////////////////////////////////// |
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142 // metafunction make_recursive_variant |
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143 // |
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144 // See docs and boost/variant/variant_fwd.hpp for more information. |
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145 // |
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146 template < BOOST_VARIANT_ENUM_PARAMS(typename T) > |
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147 struct make_recursive_variant |
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148 { |
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149 public: // metafunction result |
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150 |
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151 typedef boost::variant< |
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152 detail::variant::recursive_flag< T0 > |
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153 , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) |
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154 > type; |
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155 |
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156 }; |
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157 |
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158 /////////////////////////////////////////////////////////////////////////////// |
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159 // metafunction make_recursive_variant_over |
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160 // |
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161 // See docs and boost/variant/variant_fwd.hpp for more information. |
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162 // |
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163 template <typename Types> |
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164 struct make_recursive_variant_over |
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165 { |
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166 private: // precondition assertions |
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167 |
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168 #if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300) |
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169 BOOST_STATIC_ASSERT(( ::boost::mpl::is_sequence<Types>::value )); |
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170 #endif |
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171 |
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172 public: // metafunction result |
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173 |
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174 typedef typename make_recursive_variant< |
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175 detail::variant::over_sequence< Types > |
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176 >::type type; |
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177 |
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178 }; |
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179 |
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180 } // namespace boost |
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181 |
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182 #endif // BOOST_VARIANT_RECURSIVE_VARIANT_HPP |