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1 | //----------------------------------------------------------------------------- |
| 2 | // boost variant/recursive_wrapper_fwd.hpp header file | |
| 3 | // See http://www.boost.org for updates, documentation, and revision history. | |
| 4 | //----------------------------------------------------------------------------- | |
| 5 | // | |
| 6 | // Copyright (c) 2002 Eric Friedman, Itay Maman | |
| 7 | // Copyright (c) 2016 Antony Polukhin | |
| 8 | // | |
| 9 | // Portions Copyright (C) 2002 David Abrahams | |
| 10 | // | |
| 11 | // Distributed under the Boost Software License, Version 1.0. (See | |
| 12 | // accompanying file LICENSE_1_0.txt or copy at | |
| 13 | // http://www.boost.org/LICENSE_1_0.txt) | |
| 14 | ||
| 15 | #ifndef BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP | |
| 16 | #define BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP | |
| 17 | ||
| 18 | #include <boost/mpl/bool.hpp> | |
| 19 | #include <boost/mpl/aux_/config/ctps.hpp> | |
| 20 | #include <boost/mpl/aux_/lambda_support.hpp> | |
| 21 | #include <boost/type_traits/integral_constant.hpp> | |
| 22 | #include <boost/type_traits/is_constructible.hpp> | |
| 23 | ||
| 24 | namespace boost { | |
| 25 | ||
| 26 | ////////////////////////////////////////////////////////////////////////// | |
| 27 | // class template recursive_wrapper | |
| 28 | // | |
| 29 | // Enables recursive types in templates by breaking cyclic dependencies. | |
| 30 | // | |
| 31 | // For example: | |
| 32 | // | |
| 33 | // class my; | |
| 34 | // | |
| 35 | // typedef variant< int, recursive_wrapper<my> > var; | |
| 36 | // | |
| 37 | // class my { | |
| 38 | // var var_; | |
| 39 | // ... | |
| 40 | // }; | |
| 41 | // | |
| 42 | template <typename T> class recursive_wrapper; | |
| 43 | ||
| 44 | ||
| 45 | /////////////////////////////////////////////////////////////////////////////// | |
| 46 | // metafunction is_constructible partial specializations. | |
| 47 | // | |
| 48 | // recursive_wrapper<T> is constructible only from T and recursive_wrapper<T>. | |
| 49 | // | |
| 50 | template <class T> struct is_constructible<recursive_wrapper<T>, T> : boost::true_type{}; | |
| 51 | template <class T> struct is_constructible<recursive_wrapper<T>, const T> : boost::true_type{}; | |
| 52 | template <class T> struct is_constructible<recursive_wrapper<T>, T&> : boost::true_type{}; | |
| 53 | template <class T> struct is_constructible<recursive_wrapper<T>, const T&> : boost::true_type{}; | |
| 54 | template <class T> struct is_constructible<recursive_wrapper<T>, recursive_wrapper<T> > : boost::true_type{}; | |
| 55 | template <class T> struct is_constructible<recursive_wrapper<T>, const recursive_wrapper<T> > : boost::true_type{}; | |
| 56 | template <class T> struct is_constructible<recursive_wrapper<T>, recursive_wrapper<T>& > : boost::true_type{}; | |
| 57 | template <class T> struct is_constructible<recursive_wrapper<T>, const recursive_wrapper<T>& > : boost::true_type{}; | |
| 58 | ||
| 59 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, U > : boost::false_type{}; | |
| 60 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, const U > : boost::false_type{}; | |
| 61 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, U& > : boost::false_type{}; | |
| 62 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, const U& > : boost::false_type{}; | |
| 63 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, recursive_wrapper<U> > : boost::false_type{}; | |
| 64 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, const recursive_wrapper<U> > : boost::false_type{}; | |
| 65 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, recursive_wrapper<U>& > : boost::false_type{}; | |
| 66 | template <class T, class U> struct is_constructible<recursive_wrapper<T>, const recursive_wrapper<U>& > : boost::false_type{}; | |
| 67 | ||
| 68 | ||
| 69 | /////////////////////////////////////////////////////////////////////////////// | |
| 70 | // metafunction is_recursive_wrapper (modeled on code by David Abrahams) | |
| 71 | // | |
| 72 | // True if specified type matches recursive_wrapper<T>. | |
| 73 | // | |
| 74 | ||
| 75 | namespace detail { | |
| 76 | ||
| 77 | ||
| 78 | template <typename T> | |
| 79 | struct is_recursive_wrapper_impl | |
| 80 | : mpl::false_ | |
| 81 | { | |
| 82 | }; | |
| 83 | ||
| 84 | template <typename T> | |
| 85 | struct is_recursive_wrapper_impl< recursive_wrapper<T> > | |
| 86 | : mpl::true_ | |
| 87 | { | |
| 88 | }; | |
| 89 | ||
| 90 | ||
| 91 | } // namespace detail | |
| 92 | ||
| 93 | template< typename T > struct is_recursive_wrapper | |
| 94 | : public ::boost::integral_constant<bool,(::boost::detail::is_recursive_wrapper_impl<T>::value)> | |
| 95 | { | |
| 96 | public: | |
| 97 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_recursive_wrapper,(T)) | |
| 98 | }; | |
| 99 | ||
| 100 | /////////////////////////////////////////////////////////////////////////////// | |
| 101 | // metafunction unwrap_recursive | |
| 102 | // | |
| 103 | // If specified type T matches recursive_wrapper<U>, then U; else T. | |
| 104 | // | |
| 105 | ||
| 106 | ||
| 107 | template <typename T> | |
| 108 | struct unwrap_recursive | |
| 109 | { | |
| 110 | typedef T type; | |
| 111 | ||
| 112 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T)) | |
| 113 | }; | |
| 114 | ||
| 115 | template <typename T> | |
| 116 | struct unwrap_recursive< recursive_wrapper<T> > | |
| 117 | { | |
| 118 | typedef T type; | |
| 119 | ||
| 120 | BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,unwrap_recursive,(T)) | |
| 121 | }; | |
| 122 | ||
| 123 | ||
| 124 | } // namespace boost | |
| 125 | ||
| 126 | #endif // BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP |