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1 /*=============================================================================
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2 Copyright (c) 2001-2011 Joel de Guzman
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3
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4 Distributed under the Boost Software License, Version 1.0. (See accompanying
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5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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6 ==============================================================================*/
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7 #if !defined(FUSION_AT_05042005_0722)
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8 #define FUSION_AT_05042005_0722
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9
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10 #include <boost/mpl/int.hpp>
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11 #include <boost/type_traits/is_const.hpp>
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12 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
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13 #include <boost/fusion/support/tag_of.hpp>
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14 #include <boost/fusion/support/detail/access.hpp>
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15
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16 namespace boost { namespace fusion
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17 {
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18 // Special tags:
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19 struct sequence_facade_tag;
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20 struct boost_tuple_tag; // boost::tuples::tuple tag
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21 struct boost_array_tag; // boost::array tag
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22 struct mpl_sequence_tag; // mpl sequence tag
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23 struct std_pair_tag; // std::pair tag
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24 struct std_tuple_tag; // std::tuple tag
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25
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26 namespace extension
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27 {
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28 template <typename Tag>
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29 struct at_impl
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30 {
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31 template <typename Sequence, typename N>
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32 struct apply;
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33 };
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34
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35 template <>
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36 struct at_impl<sequence_facade_tag>
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37 {
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38 template <typename Sequence, typename N>
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39 struct apply : Sequence::template at<Sequence, N> {};
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40 };
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41
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42 template <>
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43 struct at_impl<boost_tuple_tag>;
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44
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45 template <>
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46 struct at_impl<boost_array_tag>;
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47
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48 template <>
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49 struct at_impl<mpl_sequence_tag>;
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50
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51 template <>
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52 struct at_impl<std_pair_tag>;
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53
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54 template <>
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55 struct at_impl<std_tuple_tag>;
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56 }
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57
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58 namespace result_of
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59 {
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60 template <typename Sequence, typename N>
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61 struct at
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62 : extension::at_impl<typename detail::tag_of<Sequence>::type>::
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63 template apply<Sequence, N>
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64 {};
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65
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66 template <typename Sequence, int N>
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67 struct at_c
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68 : at<Sequence, mpl::int_<N> >
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69 {};
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70 }
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71
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72
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73 template <typename N, typename Sequence>
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74 inline typename
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75 lazy_disable_if<
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76 is_const<Sequence>
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77 , result_of::at<Sequence, N>
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78 >::type
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79 at(Sequence& seq)
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80 {
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81 return result_of::at<Sequence, N>::call(seq);
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82 }
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83
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84 template <typename N, typename Sequence>
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85 inline typename result_of::at<Sequence const, N>::type
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86 at(Sequence const& seq)
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87 {
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88 return result_of::at<Sequence const, N>::call(seq);
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89 }
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90
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91 template <int N, typename Sequence>
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92 inline typename
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93 lazy_disable_if<
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94 is_const<Sequence>
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95 , result_of::at_c<Sequence, N>
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96 >::type
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97 at_c(Sequence& seq)
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98 {
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99 return fusion::at<mpl::int_<N> >(seq);
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100 }
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101
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102 template <int N, typename Sequence>
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103 inline typename result_of::at_c<Sequence const, N>::type
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104 at_c(Sequence const& seq)
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105 {
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106 return fusion::at<mpl::int_<N> >(seq);
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107 }
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108 }}
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109
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110 #endif
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111
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