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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::take_while`. | |
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_TAKE_WHILE_HPP | |
11 | #define BOOST_HANA_TAKE_WHILE_HPP | |
12 | ||
13 | #include <boost/hana/fwd/take_while.hpp> | |
14 | ||
15 | #include <boost/hana/concept/sequence.hpp> | |
16 | #include <boost/hana/config.hpp> | |
17 | #include <boost/hana/core/dispatch.hpp> | |
18 | #include <boost/hana/detail/first_unsatisfied_index.hpp> | |
19 | #include <boost/hana/take_front.hpp> | |
20 | #include <boost/hana/unpack.hpp> | |
21 | ||
22 | ||
23 | BOOST_HANA_NAMESPACE_BEGIN | |
24 | //! @cond | |
25 | template <typename Xs, typename Pred> | |
26 | constexpr auto take_while_t::operator()(Xs&& xs, Pred&& pred) const { | |
27 | using S = typename hana::tag_of<Xs>::type; | |
28 | using TakeWhile = BOOST_HANA_DISPATCH_IF(take_while_impl<S>, | |
29 | hana::Sequence<S>::value | |
30 | ); | |
31 | ||
32 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
33 | static_assert(hana::Sequence<S>::value, | |
34 | "hana::take_while(xs, pred) requires 'xs' to be a Sequence"); | |
35 | #endif | |
36 | ||
37 | return TakeWhile::apply(static_cast<Xs&&>(xs), | |
38 | static_cast<Pred&&>(pred)); | |
39 | } | |
40 | //! @endcond | |
41 | ||
42 | template <typename S, bool condition> | |
43 | struct take_while_impl<S, when<condition>> : default_ { | |
44 | template <typename Xs, typename Pred> | |
45 | static constexpr auto apply(Xs&& xs, Pred&&) { | |
46 | using FirstUnsatisfied = decltype( | |
47 | hana::unpack(static_cast<Xs&&>(xs), | |
48 | detail::first_unsatisfied_index<Pred&&>{}) | |
49 | ); | |
50 | return hana::take_front(static_cast<Xs&&>(xs), FirstUnsatisfied{}); | |
51 | } | |
52 | }; | |
53 | BOOST_HANA_NAMESPACE_END | |
54 | ||
55 | #endif // !BOOST_HANA_TAKE_WHILE_HPP |