1 | /*=============================================================================
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2 | Copyright (c) 2002-2003 Joel de Guzman
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3 | Copyright (c) 2002-2003 Hartmut Kaiser
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4 | http://spirit.sourceforge.net/
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5 |
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6 | Use, modification and distribution is subject to the Boost Software
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7 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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8 | http://www.boost.org/LICENSE_1_0.txt)
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9 | =============================================================================*/
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10 | #if !defined(BOOST_SPIRIT_SUBRULE_IPP)
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11 | #define BOOST_SPIRIT_SUBRULE_IPP
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12 |
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13 | namespace boost { namespace spirit {
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14 |
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15 | template <typename FirstT, typename RestT>
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16 | struct subrule_list;
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17 |
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18 | template <int ID, typename DefT, typename ContextT>
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19 | struct subrule_parser;
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20 |
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21 | namespace impl {
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22 |
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23 | #if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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24 |
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25 | template <int N, typename ListT>
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26 | struct get_subrule;
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27 |
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28 | template <int N, typename ListT>
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29 | struct get_subrule_chooser
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30 | {
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31 | static ListT t();
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32 | static char test(nil_t);
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33 | static int test(...);
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34 |
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35 | // Set value to
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36 | // 0: ListT is empty
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37 | // 1: ListT's first item has same ID
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38 | // 2: ListT's first item has a different ID
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39 |
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40 | enum
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41 | {
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42 | id = ListT::first_t::id,
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43 | is_same_id = N == id,
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44 | is_nil_t = sizeof(char) == sizeof(test(t())),
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45 | value = is_nil_t ? 0 : (is_same_id ? 1 : 2)
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46 | };
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47 | };
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48 |
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49 | template <int N>
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50 | struct subrule_chooser;
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51 |
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52 | template <>
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53 | struct subrule_chooser<0>
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54 | {
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55 | // First case. ListT is empty
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56 |
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57 | template <int N, typename ListT>
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58 | struct result
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59 | { typedef nil_t type; };
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60 | };
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61 |
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62 | template <>
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63 | struct subrule_chooser<1>
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64 | {
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65 | // Second case. ListT is non-empty and the list's
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66 | // first item has the ID we are looking for.
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67 |
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68 | template <int N, typename ListT>
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69 | struct result
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70 | { typedef typename ListT::first_t::def_t type; };
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71 | };
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72 |
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73 | template <>
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74 | struct subrule_chooser<2>
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75 | {
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76 | // Third case. ListT is non-empty but the list's
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77 | // first item does not have the ID we are looking for.
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78 |
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79 | template <int N, typename ListT>
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80 | struct result
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81 | { typedef typename get_subrule<N, ListT::rest_t>::type type; };
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82 | };
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83 |
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84 | template <int N, typename ListT>
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85 | struct get_subrule
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86 | {
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87 | enum { n = get_subrule_chooser<N, ListT>::value };
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88 | typedef typename subrule_chooser<n>::template
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89 | result<N, ListT>::type type;
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90 | };
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91 |
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92 | #else
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93 |
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94 | template <int N, typename ListT>
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95 | struct get_subrule
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96 | {
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97 | // First case. ListT is non-empty but the list's
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98 | // first item does not have the ID we are looking for.
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99 |
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100 | typedef typename get_subrule<N, typename ListT::rest_t>::type type;
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101 | };
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102 |
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103 | template <int ID, typename DefT, typename ContextT, typename RestT>
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104 | struct get_subrule<
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105 | ID,
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106 | subrule_list<
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107 | subrule_parser<ID, DefT, ContextT>,
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108 | RestT> >
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109 | {
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110 | // Second case. ListT is non-empty and the list's
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111 | // first item has the ID we are looking for.
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112 |
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113 | typedef DefT type;
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114 | };
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115 |
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116 | template <int ID>
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117 | struct get_subrule<ID, nil_t>
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118 | {
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119 | // Third case. ListT is empty
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120 | typedef nil_t type;
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121 | };
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122 |
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123 | #endif
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124 |
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125 | template <typename T1, typename T2>
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126 | struct get_result_t {
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127 |
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128 | // If the result type dictated by the context is nil_t (no closures
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129 | // present), then the whole subrule_parser return type is equal to
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130 | // the return type of the right hand side of this subrule_parser,
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131 | // otherwise it is equal to the dictated return value.
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132 |
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133 | typedef typename mpl::if_<
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134 | boost::is_same<T1, nil_t>, T2, T1
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135 | >::type type;
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136 | };
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137 |
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138 | template <int ID, typename ScannerT, typename ContextResultT>
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139 | struct get_subrule_result
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140 | {
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141 | typedef typename
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142 | impl::get_subrule<ID, typename ScannerT::list_t>::type
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143 | parser_t;
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144 |
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145 | typedef typename parser_result<parser_t, ScannerT>::type
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146 | def_result_t;
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147 |
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148 | typedef typename match_result<ScannerT, ContextResultT>::type
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149 | context_result_t;
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150 |
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151 | typedef typename get_result_t<context_result_t, def_result_t>::type
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152 | type;
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153 | };
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154 |
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155 | template <typename DefT, typename ScannerT, typename ContextResultT>
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156 | struct get_subrule_parser_result
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157 | {
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158 | typedef typename parser_result<DefT, ScannerT>::type
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159 | def_result_t;
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160 |
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161 | typedef typename match_result<ScannerT, ContextResultT>::type
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162 | context_result_t;
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163 |
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164 | typedef typename get_result_t<context_result_t, def_result_t>::type
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165 | type;
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166 | };
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167 |
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168 | template <typename SubruleT, int ID>
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169 | struct same_subrule_id
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170 | {
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171 | BOOST_STATIC_CONSTANT(bool, value = (SubruleT::id == ID));
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172 | };
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173 |
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174 | template <typename RT, typename ScannerT, int ID>
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175 | struct parse_subrule
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176 | {
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177 | template <typename ListT>
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178 | static void
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179 | do_parse(RT& r, ScannerT const& scan, ListT const& list, mpl::true_)
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180 | {
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181 | r = list.first.rhs.parse(scan);
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182 | }
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183 |
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184 | template <typename ListT>
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185 | static void
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186 | do_parse(RT& r, ScannerT const& scan, ListT const& list, mpl::false_)
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187 | {
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188 | typedef typename ListT::rest_t::first_t subrule_t;
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189 | mpl::bool_<same_subrule_id<subrule_t, ID>::value> same_id;
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190 | do_parse(r, scan, list.rest, same_id);
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191 | }
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192 |
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193 | static void
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194 | do_(RT& r, ScannerT const& scan)
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195 | {
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196 | typedef typename ScannerT::list_t::first_t subrule_t;
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197 | mpl::bool_<same_subrule_id<subrule_t, ID>::value> same_id;
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198 | do_parse(r, scan, scan.list, same_id);
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199 | }
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200 | };
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201 |
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202 | }}} // namespace boost::spirit::impl
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203 |
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204 | #endif
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205 |
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