boost/parameter/binding.hpp

0001 // Copyright David Abrahams 2005.
0002 // Distributed under the Boost Software License, Version 1.0.
0003 // (See accompanying file LICENSE_1_0.txt or copy at
0004 // http://www.boost.org/LICENSE_1_0.txt)
0005
0006 #ifndef BOOST_PARAMETER_BINDING_DWA200558_HPP
0007 #define BOOST_PARAMETER_BINDING_DWA200558_HPP
0008
0009 #include <boost/parameter/aux_/void.hpp>
0010 #include <boost/parameter/config.hpp>
0011
0012 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0013 #include <boost/mp11/integral.hpp>
0014 #include <boost/mp11/list.hpp>
0015 #include <boost/mp11/utility.hpp>
0016 #include <type_traits>
0017 #else
0018 #include <boost/mpl/bool.hpp>
0019 #include <boost/mpl/if.hpp>
0020 #include <boost/mpl/eval_if.hpp>
0021 #include <boost/mpl/identity.hpp>
0022 #include <boost/mpl/apply_wrap.hpp>
0023 #include <boost/mpl/assert.hpp>
0024 #include <boost/type_traits/is_same.hpp>
0025 #endif
0026
0027 namespace boost { namespace parameter {
0028
0029     // A metafunction that, given an argument pack, returns the reference type
0030     // of the parameter identified by the given keyword.  If no such parameter
0031     // has been specified, returns Default
0032
0033     template <typename Parameters, typename Keyword, typename Default>
0034     struct binding0
0035     {
0036 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0037         using type = ::boost::mp11::mp_apply_q<
0038             typename Parameters::binding
0039           , ::boost::mp11::mp_list<Keyword,Default,::boost::mp11::mp_true>
0040         >;
0041
0042         static_assert(
0043             ::boost::mp11::mp_if<
0044                 ::std::is_same<Default,::boost::parameter::void_>
0045               , ::boost::mp11::mp_if<
0046                     ::std::is_same<type,::boost::parameter::void_>
0047                   , ::boost::mp11::mp_false
0048                   , ::boost::mp11::mp_true
0049                 >
0050               , ::boost::mp11::mp_true
0051             >::value
0052           , "required parameters must not result in void_ type"
0053         );
0054 #else   // !defined(BOOST_PARAMETER_CAN_USE_MP11)
0055         typedef typename ::boost::mpl::apply_wrap3<
0056             typename Parameters::binding
0057           , Keyword
0058           , Default
0059           , ::boost::mpl::true_
0060         >::type type;
0061
0062         BOOST_MPL_ASSERT((
0063             typename ::boost::mpl::eval_if<
0064                 ::boost::is_same<Default,::boost::parameter::void_>
0065               , ::boost::mpl::if_<
0066                     ::boost::is_same<type,::boost::parameter::void_>
0067                   , ::boost::mpl::false_
0068                   , ::boost::mpl::true_
0069                 >
0070               , ::boost::mpl::true_
0071             >::type
0072         ));
0073 #endif  // BOOST_PARAMETER_CAN_USE_MP11
0074     };
0075
0076 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0077     template <typename Placeholder, typename Keyword, typename Default>
0078     struct binding1
0079     {
0080         using type = ::boost::mp11::mp_apply_q<
0081             Placeholder
0082           , ::boost::mp11::mp_list<Keyword,Default,::boost::mp11::mp_true>
0083         >;
0084
0085         static_assert(
0086             ::boost::mp11::mp_if<
0087                 ::std::is_same<Default,::boost::parameter::void_>
0088               , ::boost::mp11::mp_if<
0089                     ::std::is_same<type,::boost::parameter::void_>
0090                   , ::boost::mp11::mp_false
0091                   , ::boost::mp11::mp_true
0092                 >
0093               , ::boost::mp11::mp_true
0094             >::value
0095           , "required parameters must not result in void_ type"
0096         );
0097     };
0098 #endif  // BOOST_PARAMETER_CAN_USE_MP11
0099 }} // namespace boost::parameter
0100
0101 #include <boost/parameter/aux_/is_placeholder.hpp>
0102
0103 namespace boost { namespace parameter {
0104
0105     template <
0106         typename Parameters
0107       , typename Keyword
0108       , typename Default = ::boost::parameter::void_
0109     >
0110     struct binding
0111 #if !defined(BOOST_PARAMETER_CAN_USE_MP11)
0112       : ::boost::mpl::eval_if<
0113             ::boost::parameter::aux::is_mpl_placeholder<Parameters>
0114           , ::boost::mpl::identity<int>
0115           , ::boost::parameter::binding0<Parameters,Keyword,Default>
0116         >
0117 #endif
0118     {
0119 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0120         using type = typename ::boost::mp11::mp_if<
0121             ::boost::parameter::aux::is_mpl_placeholder<Parameters>
0122           , ::boost::mp11::mp_identity<int>
0123           , ::boost::mp11::mp_if<
0124                 ::boost::parameter::aux::is_mp11_placeholder<Parameters>
0125               , ::boost::parameter::binding1<Parameters,Keyword,Default>
0126               , ::boost::parameter::binding0<Parameters,Keyword,Default>
0127             >
0128         >::type;
0129 #endif
0130     };
0131 }} // namespace boost::parameter
0132
0133 #include <boost/parameter/aux_/result_of0.hpp>
0134
0135 namespace boost { namespace parameter {
0136
0137     // A metafunction that, given an argument pack, returns the reference type
0138     // of the parameter identified by the given keyword.  If no such parameter
0139     // has been specified, returns the type returned by invoking DefaultFn
0140     template <typename Parameters, typename Keyword, typename DefaultFn>
0141     struct lazy_binding
0142     {
0143 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0144         using type = ::boost::mp11::mp_apply_q<
0145             typename Parameters::binding
0146           , ::boost::mp11::mp_list<
0147                 Keyword
0148               , typename ::boost::parameter::aux::result_of0<DefaultFn>::type
0149               , ::boost::mp11::mp_true
0150             >
0151         >;
0152 #else
0153         typedef typename ::boost::mpl::apply_wrap3<
0154             typename Parameters::binding
0155           , Keyword
0156           , typename ::boost::parameter::aux::result_of0<DefaultFn>::type
0157           , ::boost::mpl::true_
0158         >::type type;
0159 #endif  // BOOST_PARAMETER_CAN_USE_MP11
0160     };
0161 }} // namespace boost::parameter
0162
0163 #endif  // include guard
0164