support/traits/attribute_of_binary.hpp

0001 /*=============================================================================
0002     Copyright (c) 2020 Nikita Kniazev
0003
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 =============================================================================*/
0007 #ifndef BOOST_SPIRIT_X3_SUPPORT_TRAITS_ATTRIBUTE_OF_BINARY
0008 #define BOOST_SPIRIT_X3_SUPPORT_TRAITS_ATTRIBUTE_OF_BINARY
0009
0010 #include <boost/spirit/home/x3/support/traits/attribute_of.hpp>
0011 #include <boost/spirit/home/x3/support/unused.hpp>
0012 #include <boost/type_traits/type_identity.hpp>
0013
0014 namespace boost { namespace spirit { namespace x3 { namespace detail
0015 {
0016     template <typename... T>
0017     struct type_sequence
0018     {
0019         using type = type_sequence;
0020
0021         static const int size = sizeof...(T);
0022
0023         template <typename... U>
0024         using append = type_sequence<T..., U...>;
0025
0026         template <typename... U>
0027         using prepend = type_sequence<U..., T...>;
0028
0029         template <typename U>
0030         using extend = typename U::template prepend<T...>;
0031
0032         template <template <typename...> class U>
0033         using transfer_to = U<T...>;
0034     };
0035
0036     template <typename Attribute>
0037     struct types_of_binary_init : type_sequence<Attribute> {};
0038     template <>
0039     struct types_of_binary_init<unused_type> : type_sequence<> {};
0040     template <>
0041     struct types_of_binary_init<unused_type const> : type_sequence<> {};
0042
0043     template <template <typename, typename> class B, typename P, typename C>
0044     struct get_types_of_binary
0045       : types_of_binary_init<typename traits::attribute_of<P, C>::type> {};
0046     template <template <typename, typename> class B, typename L, typename R, typename C>
0047     struct get_types_of_binary<B, B<L, R>, C>
0048       : get_types_of_binary<B, L, C>::template extend<get_types_of_binary<B, R, C>> {};
0049
0050     template <template <typename...> class A, typename T, int = T::size>
0051     struct type_sequence_to_attribute { using type = typename T::template transfer_to<A>; };
0052     template <template <typename...> class A, typename T>
0053     struct type_sequence_to_attribute<A, T, 1> : T::template transfer_to<type_identity> {};
0054     template <template <typename...> class A, typename T>
0055     struct type_sequence_to_attribute<A, T, 0> { using type = unused_type; };
0056
0057     template <template <typename...> class A, template <typename, typename> class B,
0058         typename L, typename R, typename C>
0059     using attribute_of_binary = type_sequence_to_attribute<A,
0060                                     typename get_types_of_binary<B, B<L, R>, C>::type>;
0061 }}}}
0062 #endif