parameter/aux_/tag.hpp

0001 // Copyright David Abrahams 2005.
0002 // Copyright Cromwell D. Enage 2017.
0003 // Distributed under the Boost Software License, Version 1.0.
0004 // (See accompanying file LICENSE_1_0.txt or copy at
0005 // http://www.boost.org/LICENSE_1_0.txt)
0006
0007 #ifndef BOOST_PARAMETER_AUX_TAG_DWA2005610_HPP
0008 #define BOOST_PARAMETER_AUX_TAG_DWA2005610_HPP
0009
0010 #include <boost/parameter/aux_/unwrap_cv_reference.hpp>
0011 #include <boost/parameter/aux_/tagged_argument.hpp>
0012 #include <boost/parameter/config.hpp>
0013
0014 #if defined(BOOST_PARAMETER_CAN_USE_MP11) && \
0015     !BOOST_WORKAROUND(BOOST_MSVC, >= 1910)
0016 // MSVC-14.1+ assigns rvalue references to tagged_argument instances
0017 // instead of tagged_argument_rref instances with this code.
0018 #include <boost/mp11/integral.hpp>
0019 #include <boost/mp11/utility.hpp>
0020 #include <type_traits>
0021
0022 namespace boost { namespace parameter { namespace aux {
0023
0024     template <typename Keyword, typename Arg>
0025     struct tag_if_lvalue_reference
0026     {
0027         using type = ::boost::parameter::aux::tagged_argument_list_of_1<
0028             ::boost::parameter::aux::tagged_argument<
0029                 Keyword
0030               , typename ::boost::parameter::aux
0031                 ::unwrap_cv_reference<Arg>::type
0032             >
0033         >;
0034     };
0035
0036     template <typename Keyword, typename Arg>
0037     struct tag_if_scalar
0038     {
0039         using type = ::boost::parameter::aux::tagged_argument_list_of_1<
0040             ::boost::parameter::aux
0041             ::tagged_argument<Keyword,typename ::std::add_const<Arg>::type>
0042         >;
0043     };
0044
0045     template <typename Keyword, typename Arg>
0046     using tag_if_otherwise = ::boost::mp11::mp_if<
0047         ::std::is_scalar<typename ::std::remove_const<Arg>::type>
0048       , ::boost::parameter::aux::tag_if_scalar<Keyword,Arg>
0049       , ::boost::mp11::mp_identity<
0050             ::boost::parameter::aux::tagged_argument_list_of_1<
0051                 ::boost::parameter::aux::tagged_argument_rref<Keyword,Arg>
0052             >
0053         >
0054     >;
0055
0056     template <typename Keyword, typename Arg>
0057     using tag = ::boost::mp11::mp_if<
0058         ::boost::mp11::mp_if<
0059             ::std::is_lvalue_reference<Arg>
0060           , ::boost::mp11::mp_true
0061           , ::boost::parameter::aux::is_cv_reference_wrapper<Arg>
0062         >
0063       , ::boost::parameter::aux::tag_if_lvalue_reference<Keyword,Arg>
0064       , ::boost::parameter::aux::tag_if_otherwise<Keyword,Arg>
0065     >;
0066 }}} // namespace boost::parameter::aux_
0067
0068 #elif defined(BOOST_PARAMETER_HAS_PERFECT_FORWARDING)
0069 #include <boost/mpl/bool.hpp>
0070 #include <boost/mpl/if.hpp>
0071 #include <boost/mpl/eval_if.hpp>
0072 #include <boost/mpl/identity.hpp>
0073 #include <boost/type_traits/add_const.hpp>
0074 #include <boost/type_traits/is_scalar.hpp>
0075 #include <boost/type_traits/is_lvalue_reference.hpp>
0076 #include <boost/type_traits/remove_const.hpp>
0077
0078 namespace boost { namespace parameter { namespace aux {
0079
0080     template <typename Keyword, typename ActualArg>
0081     struct tag
0082     {
0083         typedef typename ::boost::parameter::aux
0084         ::unwrap_cv_reference<ActualArg>::type Arg;
0085         typedef typename ::boost::add_const<Arg>::type ConstArg;
0086         typedef typename ::boost::remove_const<Arg>::type MutArg;
0087         typedef typename ::boost::mpl::eval_if<
0088             typename ::boost::mpl::if_<
0089                 ::boost::is_lvalue_reference<ActualArg>
0090               , ::boost::mpl::true_
0091               , ::boost::parameter::aux::is_cv_reference_wrapper<ActualArg>
0092             >::type
0093           , ::boost::mpl::identity<
0094 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0095                 ::boost::parameter::aux::tagged_argument_list_of_1<
0096 #endif
0097                     ::boost::parameter::aux::tagged_argument<Keyword,Arg>
0098 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0099                 >
0100 #endif
0101             >
0102           , ::boost::mpl::if_<
0103                 ::boost::is_scalar<MutArg>
0104 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0105               , ::boost::parameter::aux::tagged_argument_list_of_1<
0106                     ::boost::parameter::aux::tagged_argument<Keyword,ConstArg>
0107                 >
0108               , ::boost::parameter::aux::tagged_argument_list_of_1<
0109                     ::boost::parameter::aux::tagged_argument_rref<Keyword,Arg>
0110                 >
0111 #else
0112               , ::boost::parameter::aux::tagged_argument<Keyword,ConstArg>
0113               , ::boost::parameter::aux::tagged_argument_rref<Keyword,Arg>
0114 #endif
0115             >
0116         >::type type;
0117     };
0118 }}} // namespace boost::parameter::aux_
0119
0120 #else   // !defined(BOOST_PARAMETER_HAS_PERFECT_FORWARDING)
0121
0122 namespace boost { namespace parameter { namespace aux {
0123
0124     template <
0125         typename Keyword
0126       , typename Arg
0127 #if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564))
0128       , typename = typename ::boost::parameter::aux
0129         ::is_cv_reference_wrapper<Arg>::type
0130 #endif
0131     >
0132     struct tag
0133     {
0134         typedef ::boost::parameter::aux::tagged_argument<
0135             Keyword
0136           , typename ::boost::parameter::aux::unwrap_cv_reference<Arg>::type
0137         > type;
0138     };
0139 }}} // namespace boost::parameter::aux_
0140
0141 #if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564))
0142 #include <boost/mpl/bool.hpp>
0143 #include <boost/type_traits/remove_reference.hpp>
0144
0145 namespace boost { namespace parameter { namespace aux {
0146
0147     template <typename Keyword, typename Arg>
0148     struct tag<Keyword,Arg,::boost::mpl::false_>
0149     {
0150         typedef ::boost::parameter::aux::tagged_argument<
0151             Keyword
0152           , typename ::boost::remove_reference<Arg>::type
0153         > type;
0154     };
0155 }}} // namespace boost::parameter::aux_
0156
0157 #endif  // Borland workarounds needed.
0158 #endif  // MP11 or perfect forwarding support
0159 #endif  // include guard
0160