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1 /*=============================================================================
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2 Copyright (c) 2001-2007 Joel de Guzman
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3 Copyright (c) 2004 Daniel Wallin
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4
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5 Distributed under the Boost Software License, Version 1.0. (See accompanying
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6 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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7 ==============================================================================*/
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8 #ifndef PHOENIX_SCOPE_LET_HPP
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9 #define PHOENIX_SCOPE_LET_HPP
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10
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11 #include <boost/spirit/home/phoenix/core/limits.hpp>
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12 #include <boost/spirit/home/phoenix/core/composite.hpp>
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13 #include <boost/spirit/home/phoenix/scope/scoped_environment.hpp>
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14 #include <boost/spirit/home/phoenix/scope/detail/local_variable.hpp>
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15 #include <boost/spirit/home/phoenix/detail/local_reference.hpp>
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16 #include <boost/spirit/home/phoenix/core/actor.hpp>
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17 #include <boost/fusion/include/transform.hpp>
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18 #include <boost/fusion/include/as_vector.hpp>
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19 #include <boost/mpl/eval_if.hpp>
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20 #include <boost/mpl/bool.hpp>
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21
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22 namespace boost { namespace phoenix
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23 {
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24 template <typename Base, typename Vars, typename Map>
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25 struct let_actor : Base
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26 {
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27 typedef typename
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28 mpl::fold<
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29 Vars
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30 , mpl::false_
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31 , detail::compute_no_nullary
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32 >::type
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33 no_nullary;
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34
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35 template <typename Env>
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36 struct result
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37 {
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38 typedef typename
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39 fusion::result_of::as_vector<
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40 typename fusion::result_of::transform<
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41 Vars
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42 , detail::initialize_local<Env>
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43 >::type
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44 >::type
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45 locals_type;
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46
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47 typedef typename Base::template
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48 result<scoped_environment<Env, Env, locals_type, Map> >::type
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49 result_type;
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50
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51 typedef typename
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52 detail::unwrap_local_reference<result_type>::type
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53 type;
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54 };
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55
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56 let_actor(Base const& base, Vars const& vars)
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57 : Base(base), vars(vars) {}
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58
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59 template <typename Env>
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60 typename result<Env>::type
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61 eval(Env const& env) const
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62 {
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63 typedef typename
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64 fusion::result_of::as_vector<
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65 typename fusion::result_of::transform<
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66 Vars
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67 , detail::initialize_local<Env>
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68 >::type
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69 >::type
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70 locals_type;
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71
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72 locals_type locals =
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73 fusion::as_vector(
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74 fusion::transform(
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75 vars
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76 , detail::initialize_local<Env>(env)));
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77
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78 typedef typename result<Env>::type RT;
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79 return RT(Base::eval(
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80 scoped_environment<Env, Env, locals_type, Map>(
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81 env
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82 , env
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83 , locals)));
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84 }
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85
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86 Vars vars;
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87 };
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88
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89 template <typename Vars, typename Map>
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90 struct let_actor_gen
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91 {
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92 template <typename Base>
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93 actor<let_actor<Base, Vars, Map> > const
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94 operator[](actor<Base> const& base) const
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95 {
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96 return let_actor<Base, Vars, Map>(base, vars);
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97 }
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98
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99 let_actor_gen(Vars const& vars)
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100 : vars(vars) {}
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101
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102 Vars vars;
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103 };
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104
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105 template <typename Key>
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106 struct local_variable; // forward
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107 struct assign_eval; // forward
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108
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109 struct let_gen
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110 {
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111 template <typename K0, typename V0>
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112 let_actor_gen<
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113 fusion::vector<V0>
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114 , detail::map_local_index_to_tuple<K0>
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115 >
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116 operator()(
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117 actor<composite<assign_eval, fusion::vector<local_variable<K0>, V0> > > const& a0
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118 ) const
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119 {
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120 return fusion::vector<V0>(fusion::at_c<1>(a0));
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121 }
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122
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123 template <typename K0, typename K1, typename V0, typename V1>
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124 let_actor_gen<
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125 fusion::vector<V0, V1>
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126 , detail::map_local_index_to_tuple<K0, K1>
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127 >
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128 operator()(
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129 actor<composite<assign_eval, fusion::vector<local_variable<K0>, V0> > > const& a0
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130 , actor<composite<assign_eval, fusion::vector<local_variable<K1>, V1> > > const& a1
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131 ) const
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132 {
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133 return fusion::vector<V0, V1>(fusion::at_c<1>(a0), fusion::at_c<1>(a1));
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134 }
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135
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136 // Bring in the rest...
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137 #define PHOENIX_LOCAL_GEN_NAME let_actor_gen
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138 #include <boost/spirit/home/phoenix/scope/detail/local_gen.hpp>
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139 #undef PHOENIX_LOCAL_GEN_NAME
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140 };
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141
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142 let_gen const let = let_gen();
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143 }}
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144
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145 #endif
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