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1 //-----------------------------------------------------------------------------
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2 // boost variant/detail/apply_visitor_delayed.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) 2002-2003
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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_DETAIL_APPLY_VISITOR_DELAYED_HPP
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14 #define BOOST_VARIANT_DETAIL_APPLY_VISITOR_DELAYED_HPP
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15
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16 #include "boost/variant/detail/generic_result_type.hpp"
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17
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18 #include "boost/variant/detail/apply_visitor_unary.hpp"
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19 #include "boost/variant/detail/apply_visitor_binary.hpp"
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20 #include "boost/variant/variant_fwd.hpp" // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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21
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22
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23 #include "boost/variant/detail/has_result_type.hpp"
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24 #include <boost/core/enable_if.hpp>
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25
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26 namespace boost {
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27
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28 //////////////////////////////////////////////////////////////////////////
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29 // function template apply_visitor(visitor)
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30 //
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31 // Returns a function object, overloaded for unary and binary usage, that
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32 // visits its arguments using visitor (or a copy of visitor) via
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33 // * apply_visitor( visitor, [argument] )
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34 // under unary invocation, or
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35 // * apply_visitor( visitor, [argument1], [argument2] )
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36 // under binary invocation.
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37 //
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38 // NOTE: Unlike other apply_visitor forms, the visitor object must be
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39 // non-const; this prevents user from giving temporary, to disastrous
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40 // effect (i.e., returned function object would have dead reference).
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41 //
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42
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43 template <typename Visitor>
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44 class apply_visitor_delayed_t
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45 {
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46 public: // visitor typedefs
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47
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48 typedef typename Visitor::result_type
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49 result_type;
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50
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51 private: // representation
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52
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53 Visitor& visitor_;
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54
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55 public: // structors
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56
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57 explicit apply_visitor_delayed_t(Visitor& visitor) BOOST_NOEXCEPT
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58 : visitor_(visitor)
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59 {
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60 }
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61
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62 #if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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63
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64 public: // N-ary visitor interface
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65 template <typename... Visitables>
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66 BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
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67 operator()(Visitables&... visitables) const
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68 {
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69 return apply_visitor(visitor_, visitables...);
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70 }
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71
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72 #else // !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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73
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74 public: // unary visitor interface
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75
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76 template <typename Visitable>
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77 BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
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78 operator()(Visitable& visitable) const
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79 {
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80 return apply_visitor(visitor_, visitable);
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81 }
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82
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83 public: // binary visitor interface
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84
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85 template <typename Visitable1, typename Visitable2>
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86 BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
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87 operator()(Visitable1& visitable1, Visitable2& visitable2) const
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88 {
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89 return apply_visitor(visitor_, visitable1, visitable2);
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90 }
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91
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92 #endif // !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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93
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94 private:
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95 apply_visitor_delayed_t& operator=(const apply_visitor_delayed_t&);
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96
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97 };
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98
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99 template <typename Visitor>
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100 inline typename boost::enable_if<
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101 boost::detail::variant::has_result_type<Visitor>,
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102 apply_visitor_delayed_t<Visitor>
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103 >::type apply_visitor(Visitor& visitor)
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104 {
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105 return apply_visitor_delayed_t<Visitor>(visitor);
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106 }
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107
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108 #if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276) \
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109 && !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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110
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111 template <typename Visitor>
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112 class apply_visitor_delayed_cpp14_t
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113 {
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114 private: // representation
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115 Visitor& visitor_;
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116
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117 public: // structors
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118
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119 explicit apply_visitor_delayed_cpp14_t(Visitor& visitor) BOOST_NOEXCEPT
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120 : visitor_(visitor)
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121 {
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122 }
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123
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124 public: // N-ary visitor interface
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125 template <typename... Visitables>
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126 decltype(auto) operator()(Visitables&... visitables) const
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127 {
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128 return apply_visitor(visitor_, visitables...);
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129 }
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130
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131 private:
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132 apply_visitor_delayed_cpp14_t& operator=(const apply_visitor_delayed_cpp14_t&);
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133
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134 };
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135
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136 template <typename Visitor>
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137 inline typename boost::disable_if<
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138 boost::detail::variant::has_result_type<Visitor>,
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139 apply_visitor_delayed_cpp14_t<Visitor>
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140 >::type apply_visitor(Visitor& visitor)
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141 {
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142 return apply_visitor_delayed_cpp14_t<Visitor>(visitor);
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143 }
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144
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145 #endif // !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
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146 // && !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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147
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148
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149 } // namespace boost
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150
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151 #endif // BOOST_VARIANT_DETAIL_APPLY_VISITOR_DELAYED_HPP
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