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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::count`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
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_COUNT_HPP | |
11 | #define BOOST_HANA_COUNT_HPP | |
12 | ||
13 | #include <boost/hana/fwd/count.hpp> | |
14 | ||
15 | #include <boost/hana/concept/foldable.hpp> | |
16 | #include <boost/hana/config.hpp> | |
17 | #include <boost/hana/core/dispatch.hpp> | |
18 | #include <boost/hana/count_if.hpp> | |
19 | #include <boost/hana/equal.hpp> | |
20 | ||
21 | ||
22 | BOOST_HANA_NAMESPACE_BEGIN | |
23 | //! @cond | |
24 | template <typename Xs, typename Value> | |
25 | constexpr auto count_t::operator()(Xs&& xs, Value&& value) const { | |
26 | using S = typename hana::tag_of<Xs>::type; | |
27 | using Count = BOOST_HANA_DISPATCH_IF(count_impl<S>, | |
28 | hana::Foldable<S>::value | |
29 | ); | |
30 | ||
31 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
32 | static_assert(hana::Foldable<S>::value, | |
33 | "hana::count(xs, value) requires 'xs' to be Foldable"); | |
34 | #endif | |
35 | ||
36 | return Count::apply(static_cast<Xs&&>(xs), static_cast<Value&&>(value)); | |
37 | } | |
38 | //! @endcond | |
39 | ||
40 | template <typename T, bool condition> | |
41 | struct count_impl<T, when<condition>> : default_ { | |
42 | template <typename Xs, typename Value> | |
43 | static constexpr auto apply(Xs&& xs, Value&& value) { | |
44 | return hana::count_if(static_cast<Xs&&>(xs), | |
45 | hana::equal.to(static_cast<Value&&>(value))); | |
46 | } | |
47 | }; | |
48 | BOOST_HANA_NAMESPACE_END | |
49 | ||
50 | #endif // !BOOST_HANA_COUNT_HPP |