1/*!
2@file
3Defines `boost::hana::take_while`.
4
5Copyright Louis Dionne 2013-2022
6Distributed 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
23namespace boost { namespace hana {
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}} // end namespace boost::hana
54
55#endif // !BOOST_HANA_TAKE_WHILE_HPP
56

source code of boost/libs/hana/include/boost/hana/take_while.hpp