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- /*!
- @file
- Defines `boost::hana::lift`.
- @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_LIFT_HPP
- #define BOOST_HANA_LIFT_HPP
- #include <boost/hana/fwd/lift.hpp>
- #include <boost/hana/concept/applicative.hpp>
- #include <boost/hana/concept/sequence.hpp>
- #include <boost/hana/config.hpp>
- #include <boost/hana/core/dispatch.hpp>
- #include <boost/hana/core/make.hpp>
- BOOST_HANA_NAMESPACE_BEGIN
- //! @cond
- template <typename A>
- template <typename X>
- constexpr auto lift_t<A>::operator()(X&& x) const {
- #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
- static_assert(hana::Applicative<A>::value,
- "hana::lift<A> requires 'A' to be an Applicative");
- #endif
- using Lift = BOOST_HANA_DISPATCH_IF(lift_impl<A>,
- hana::Applicative<A>::value
- );
- return Lift::apply(static_cast<X&&>(x));
- }
- //! @endcond
- template <typename A, bool condition>
- struct lift_impl<A, when<condition>> : default_ {
- template <typename ...Args>
- static constexpr auto apply(Args&& ...args) = delete;
- };
- template <typename S>
- struct lift_impl<S, when<Sequence<S>::value>> {
- template <typename X>
- static constexpr decltype(auto) apply(X&& x)
- { return hana::make<S>(static_cast<X&&>(x)); }
- };
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_LIFT_HPP
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