1 /*!
2 @file
3 Defines `boost::hana::is_subset`.
4 
5 @copyright Louis Dionne 2013-2017
6 Distributed under the Boost Software License, Version 1.0.
7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
8  */
9 
10 #ifndef BOOST_HANA_IS_SUBSET_HPP
11 #define BOOST_HANA_IS_SUBSET_HPP
12 
13 #include <boost/hana/fwd/is_subset.hpp>
14 
15 #include <boost/hana/all_of.hpp>
16 #include <boost/hana/concept/searchable.hpp>
17 #include <boost/hana/config.hpp>
18 #include <boost/hana/contains.hpp>
19 #include <boost/hana/core/common.hpp>
20 #include <boost/hana/core/to.hpp>
21 #include <boost/hana/core/dispatch.hpp>
22 #include <boost/hana/detail/has_common_embedding.hpp>
23 #include <boost/hana/functional/partial.hpp>
24 
25 
26 BOOST_HANA_NAMESPACE_BEGIN
27     //! @cond
28     template <typename Xs, typename Ys>
operator ()(Xs && xs,Ys && ys) const29     constexpr auto is_subset_t::operator()(Xs&& xs, Ys&& ys) const {
30         using S1 = typename hana::tag_of<Xs>::type;
31         using S2 = typename hana::tag_of<Ys>::type;
32         using IsSubset = BOOST_HANA_DISPATCH_IF(
33             decltype(is_subset_impl<S1, S2>{}),
34             hana::Searchable<S1>::value &&
35             hana::Searchable<S2>::value &&
36             !is_default<is_subset_impl<S1, S2>>::value
37         );
38 
39     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
40         static_assert(hana::Searchable<S1>::value,
41         "hana::is_subset(xs, ys) requires 'xs' to be Searchable");
42 
43         static_assert(hana::Searchable<S2>::value,
44         "hana::is_subset(xs, ys) requires 'ys' to be Searchable");
45 
46         static_assert(!is_default<is_subset_impl<S1, S2>>::value,
47         "hana::is_subset(xs, ys) requires 'xs' and 'ys' to be embeddable "
48         "in a common Searchable");
49     #endif
50 
51         return IsSubset::apply(static_cast<Xs&&>(xs), static_cast<Ys&&>(ys));
52     }
53     //! @endcond
54 
55     template <typename S1, typename S2, bool condition>
56     struct is_subset_impl<S1, S2, when<condition>> : default_ {
57         template <typename ...Args>
58         static constexpr auto apply(Args&& ...) = delete;
59     };
60 
61     template <typename S, bool condition>
62     struct is_subset_impl<S, S, when<condition>> {
63         template <typename Xs, typename Ys>
applyis_subset_impl64         static constexpr decltype(auto) apply(Xs&& xs, Ys&& ys) {
65             return hana::all_of(static_cast<Xs&&>(xs),
66                     hana::partial(hana::contains, static_cast<Ys&&>(ys)));
67         }
68     };
69 
70     // Cross-type overload
71     template <typename S1, typename S2>
72     struct is_subset_impl<S1, S2, when<
73         detail::has_nontrivial_common_embedding<Searchable, S1, S2>::value
74     >> {
75         using C = typename common<S1, S2>::type;
76         template <typename Xs, typename Ys>
applyis_subset_impl77         static constexpr decltype(auto) apply(Xs&& xs, Ys&& ys) {
78             return hana::is_subset(hana::to<C>(static_cast<Xs&&>(xs)),
79                                    hana::to<C>(static_cast<Ys&&>(ys)));
80         }
81     };
82 BOOST_HANA_NAMESPACE_END
83 
84 #endif // !BOOST_HANA_IS_SUBSET_HPP
85