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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::repeat`. | |
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_REPEAT_HPP | |
11 | #define BOOST_HANA_REPEAT_HPP | |
12 | ||
13 | #include <boost/hana/fwd/repeat.hpp> | |
14 | ||
15 | #include <boost/hana/concept/integral_constant.hpp> | |
16 | #include <boost/hana/config.hpp> | |
17 | #include <boost/hana/core/dispatch.hpp> | |
18 | ||
19 | #include <cstddef> | |
20 | #include <utility> | |
21 | ||
22 | ||
23 | BOOST_HANA_NAMESPACE_BEGIN | |
24 | template <typename I, bool condition> | |
25 | struct repeat_impl<I, when<condition>> : default_ { | |
26 | template <typename F, std::size_t ...i> | |
27 | static constexpr void repeat_helper(F&& f, std::index_sequence<i...>) { | |
28 | using Swallow = std::size_t[]; | |
29 | (void)Swallow{0, ((void)f(), i)...}; | |
30 | } | |
31 | ||
32 | template <typename N, typename F> | |
33 | static constexpr auto apply(N const&, F&& f) { | |
34 | static_assert(N::value >= 0, "hana::repeat(n, f) requires 'n' to be non-negative"); | |
35 | constexpr std::size_t n = N::value; | |
36 | repeat_helper(static_cast<F&&>(f), std::make_index_sequence<n>{}); | |
37 | } | |
38 | }; | |
39 | ||
40 | //! @cond | |
41 | template <typename N, typename F> | |
42 | constexpr void repeat_t::operator()(N const& n, F&& f) const { | |
43 | using I = typename hana::tag_of<N>::type; | |
44 | using Repeat = BOOST_HANA_DISPATCH_IF(repeat_impl<I>, | |
45 | hana::IntegralConstant<I>::value | |
46 | ); | |
47 | ||
48 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
49 | static_assert(hana::IntegralConstant<I>::value, | |
50 | "hana::repeat(n, f) requires 'n' to be an IntegralConstant"); | |
51 | #endif | |
52 | ||
53 | return Repeat::apply(n, static_cast<F&&>(f)); | |
54 | } | |
55 | //! @endcond | |
56 | BOOST_HANA_NAMESPACE_END | |
57 | ||
58 | #endif // !BOOST_HANA_REPEAT_HPP |