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/*!
@file
Defines `boost::hana::none`.
@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_NONE_HPP
#define BOOST_HANA_NONE_HPP
#include <boost/hana/fwd/none.hpp>
#include <boost/hana/concept/searchable.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/functional/id.hpp>
#include <boost/hana/none_of.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename Xs>
constexpr auto none_t::operator()(Xs&& xs) const {
using S = typename hana::tag_of<Xs>::type;
using None = BOOST_HANA_DISPATCH_IF(none_impl<S>,
hana::Searchable<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Searchable<S>::value,
"hana::none(xs) requires 'xs' to be a Searchable");
#endif
return None::apply(static_cast<Xs&&>(xs));
}
//! @endcond
template <typename S, bool condition>
struct none_impl<S, when<condition>> : default_ {
template <typename Xs>
static constexpr auto apply(Xs&& xs)
{ return hana::none_of(static_cast<Xs&&>(xs), hana::id); }
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_NONE_HPP
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