3 Defines `boost::hana::is_subset`.
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)
10 #ifndef BOOST_HANA_IS_SUBSET_HPP
11 #define BOOST_HANA_IS_SUBSET_HPP
13 #include <boost/hana/fwd/is_subset.hpp>
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>
26 namespace boost { namespace hana {
28 template <typename Xs, typename Ys>
29 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
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");
43 static_assert(hana::Searchable<S2>::value,
44 "hana::is_subset(xs, ys) requires 'ys' to be Searchable");
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");
51 return IsSubset::apply(static_cast<Xs&&>(xs), static_cast<Ys&&>(ys));
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;
61 template <typename S, bool condition>
62 struct is_subset_impl<S, S, when<condition>> {
63 template <typename Xs, typename Ys>
64 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)));
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
75 using C = typename common<S1, S2>::type;
76 template <typename Xs, typename Ys>
77 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)));
82 }} // end namespace boost::hana
84 #endif // !BOOST_HANA_IS_SUBSET_HPP