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/*!
@file
Defines `boost::hana::take_while`.
@copyright Louis Dionne 2013-2016
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_HANA_TAKE_WHILE_HPP
#define BOOST_HANA_TAKE_WHILE_HPP
#include <boost/hana/fwd/take_while.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/detail/first_unsatisfied_index.hpp>
#include <boost/hana/take_front.hpp>
#include <boost/hana/unpack.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename Xs, typename Pred>
constexpr auto take_while_t::operator()(Xs&& xs, Pred&& pred) const {
using S = typename hana::tag_of<Xs>::type;
using TakeWhile = BOOST_HANA_DISPATCH_IF(take_while_impl<S>,
hana::Sequence<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Sequence<S>::value,
"hana::take_while(xs, pred) requires 'xs' to be a Sequence");
#endif
return TakeWhile::apply(static_cast<Xs&&>(xs),
static_cast<Pred&&>(pred));
}
//! @endcond
template <typename S, bool condition>
struct take_while_impl<S, when<condition>> : default_ {
template <typename Xs, typename Pred>
static constexpr auto apply(Xs&& xs, Pred&&) {
using FirstUnsatisfied = decltype(
hana::unpack(static_cast<Xs&&>(xs),
detail::first_unsatisfied_index<Pred&&>{})
);
return hana::take_front(static_cast<Xs&&>(xs), FirstUnsatisfied{});
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_TAKE_WHILE_HPP
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