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1 //-----------------------------------------------------------------------------
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2 // boost variant/detail/enable_recursive_fwd.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_DETAIL_ENABLE_RECURSIVE_FWD_HPP
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14 #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
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15
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16 #include "boost/mpl/aux_/config/ctps.hpp"
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17
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18 #include "boost/mpl/bool_fwd.hpp"
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19
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20 # include "boost/mpl/bool.hpp"
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21
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22 namespace boost {
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23 namespace detail { namespace variant {
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24
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25 ///////////////////////////////////////////////////////////////////////////////
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26 // (detail) tag recursive_flag
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27 //
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28 // Signifies that the variant should perform recursive substituion.
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29 //
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30
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31
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32 template <typename T>
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33 struct recursive_flag
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34 {
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35 typedef T type;
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36 };
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37
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38
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39 ///////////////////////////////////////////////////////////////////////////////
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40 // (detail) metafunction is_recursive_flag
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41 //
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42 // Signifies that the variant should perform recursive substituion.
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43 //
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44
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45
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46 template <typename T>
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47 struct is_recursive_flag
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48 : mpl::false_
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49 {
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50 };
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51
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52 template <typename T>
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53 struct is_recursive_flag< recursive_flag<T> >
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54 : mpl::true_
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55 {
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56 };
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57
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58
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59 ///////////////////////////////////////////////////////////////////////////////
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60 // (detail) metafunction enable_recursive
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61 //
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62 // Attempts recursive_variant_ tag substitution, wrapping with
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63 // boost::recursive_wrapper if substituion occurs w/ non-indirect result
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64 // (i.e., not a reference or pointer) *and* NoWrapper is false_.
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65 //
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66 template <
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67 typename T
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68 , typename RecursiveVariant
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69 , typename NoWrapper = mpl::false_
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70 >
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71 struct enable_recursive;
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72
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73 ///////////////////////////////////////////////////////////////////////////////
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74 // (detail) metafunction class quoted_enable_recursive
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75 //
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76 // Same behavior as enable_recursive metafunction (see above).
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77 //
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78 template <
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79 typename RecursiveVariant
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80 , typename NoWrapper = mpl::false_
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81 >
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82 struct quoted_enable_recursive;
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83
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84 }} // namespace detail::variant
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85 } // namespace boost
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86
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87 #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
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