boost/hana/is_subset.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::is_subset`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_IS_SUBSET_HPP
0011 #define BOOST_HANA_IS_SUBSET_HPP
0012
0013 #include <boost/hana/fwd/is_subset.hpp>
0014
0015 #include <boost/hana/all_of.hpp>
0016 #include <boost/hana/concept/searchable.hpp>
0017 #include <boost/hana/config.hpp>
0018 #include <boost/hana/contains.hpp>
0019 #include <boost/hana/core/common.hpp>
0020 #include <boost/hana/core/to.hpp>
0021 #include <boost/hana/core/dispatch.hpp>
0022 #include <boost/hana/detail/has_common_embedding.hpp>
0023 #include <boost/hana/functional/partial.hpp>
0024
0025
0026 namespace boost { namespace hana {
0027     //! @cond
0028     template <typename Xs, typename Ys>
0029     constexpr auto is_subset_t::operator()(Xs&& xs, Ys&& ys) const {
0030         using S1 = typename hana::tag_of<Xs>::type;
0031         using S2 = typename hana::tag_of<Ys>::type;
0032         using IsSubset = BOOST_HANA_DISPATCH_IF(
0033             decltype(is_subset_impl<S1, S2>{}),
0034             hana::Searchable<S1>::value &&
0035             hana::Searchable<S2>::value &&
0036             !is_default<is_subset_impl<S1, S2>>::value
0037         );
0038
0039     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0040         static_assert(hana::Searchable<S1>::value,
0041         "hana::is_subset(xs, ys) requires 'xs' to be Searchable");
0042
0043         static_assert(hana::Searchable<S2>::value,
0044         "hana::is_subset(xs, ys) requires 'ys' to be Searchable");
0045
0046         static_assert(!is_default<is_subset_impl<S1, S2>>::value,
0047         "hana::is_subset(xs, ys) requires 'xs' and 'ys' to be embeddable "
0048         "in a common Searchable");
0049     #endif
0050
0051         return IsSubset::apply(static_cast<Xs&&>(xs), static_cast<Ys&&>(ys));
0052     }
0053     //! @endcond
0054
0055     template <typename S1, typename S2, bool condition>
0056     struct is_subset_impl<S1, S2, when<condition>> : default_ {
0057         template <typename ...Args>
0058         static constexpr auto apply(Args&& ...) = delete;
0059     };
0060
0061     template <typename S, bool condition>
0062     struct is_subset_impl<S, S, when<condition>> {
0063         template <typename Xs, typename Ys>
0064         static constexpr decltype(auto) apply(Xs&& xs, Ys&& ys) {
0065             return hana::all_of(static_cast<Xs&&>(xs),
0066                     hana::partial(hana::contains, static_cast<Ys&&>(ys)));
0067         }
0068     };
0069
0070     // Cross-type overload
0071     template <typename S1, typename S2>
0072     struct is_subset_impl<S1, S2, when<
0073         detail::has_nontrivial_common_embedding<Searchable, S1, S2>::value
0074     >> {
0075         using C = typename common<S1, S2>::type;
0076         template <typename Xs, typename Ys>
0077         static constexpr decltype(auto) apply(Xs&& xs, Ys&& ys) {
0078             return hana::is_subset(hana::to<C>(static_cast<Xs&&>(xs)),
0079                                    hana::to<C>(static_cast<Ys&&>(ys)));
0080         }
0081     };
0082 }} // end namespace boost::hana
0083
0084 #endif // !BOOST_HANA_IS_SUBSET_HPP