63e88f80
 Hu Chunming
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/*!
@file
Defines `boost::hana::find`.
Copyright Louis Dionne 2013-2022
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_FIND_HPP
#define BOOST_HANA_FIND_HPP
#include <boost/hana/fwd/find.hpp>
#include <boost/hana/concept/searchable.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/find_if.hpp>
namespace boost { namespace hana {
//! @cond
template <typename Xs, typename Key>
constexpr auto find_t::operator()(Xs&& xs, Key const& key) const {
using S = typename hana::tag_of<Xs>::type;
using Find = BOOST_HANA_DISPATCH_IF(find_impl<S>,
hana::Searchable<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Searchable<S>::value,
"hana::find(xs, key) requires 'xs' to be Searchable");
#endif
return Find::apply(static_cast<Xs&&>(xs), key);
}
//! @endcond
namespace detail {
template <typename T>
struct equal_to {
T const& t;
template <typename U>
constexpr auto operator()(U const& u) const {
return hana::equal(t, u);
}
};
}
template <typename S, bool condition>
struct find_impl<S, when<condition>> : default_ {
template <typename Xs, typename Key>
static constexpr auto apply(Xs&& xs, Key const& key) {
return hana::find_if(static_cast<Xs&&>(xs),
detail::equal_to<Key>{key});
}
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_FIND_HPP
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