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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::for_each`. | |
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_FOR_EACH_HPP | |
11 | #define BOOST_HANA_FOR_EACH_HPP | |
12 | ||
13 | #include <boost/hana/fwd/for_each.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/unpack.hpp> | |
19 | ||
20 | ||
21 | BOOST_HANA_NAMESPACE_BEGIN | |
22 | //! @cond | |
23 | template <typename Xs, typename F> | |
24 | constexpr void for_each_t::operator()(Xs&& xs, F&& f) const { | |
25 | using S = typename hana::tag_of<Xs>::type; | |
26 | using ForEach = BOOST_HANA_DISPATCH_IF(for_each_impl<S>, | |
27 | hana::Foldable<S>::value | |
28 | ); | |
29 | ||
30 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
31 | static_assert(hana::Foldable<S>::value, | |
32 | "hana::for_each(xs, f) requires 'xs' to be Foldable"); | |
33 | #endif | |
34 | ||
35 | return ForEach::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f)); | |
36 | } | |
37 | //! @endcond | |
38 | ||
39 | namespace detail { | |
40 | template <typename F> | |
41 | struct on_each { | |
42 | F f; | |
43 | template <typename ...Xs> | |
44 | constexpr void operator()(Xs&& ...xs) const { | |
45 | using Swallow = int[]; | |
46 | (void)Swallow{0, ((void)(*f)(static_cast<Xs&&>(xs)), 0)...}; | |
47 | } | |
48 | }; | |
49 | } | |
50 | ||
51 | template <typename T, bool condition> | |
52 | struct for_each_impl<T, when<condition>> : default_ { | |
53 | template <typename Xs, typename F> | |
54 | static constexpr void apply(Xs&& xs, F&& f) { | |
55 | // We use a pointer instead of a reference to avoid a Clang ICE. | |
56 | hana::unpack(static_cast<Xs&&>(xs), | |
57 | detail::on_each<decltype(&f)>{&f}); | |
58 | } | |
59 | }; | |
60 | BOOST_HANA_NAMESPACE_END | |
61 | ||
62 | #endif // !BOOST_HANA_FOR_EACH_HPP |