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- /*!
- @file
- Defines `boost::hana::find`.
- @copyright Louis Dionne 2013-2017
- 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>
- BOOST_HANA_NAMESPACE_BEGIN
- //! @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});
- }
- };
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_FIND_HPP
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