76 lines
2.2 KiB
C++
76 lines
2.2 KiB
C++
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/*!
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@file
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Defines `boost::hana::not_`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_NOT_HPP
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#define BOOST_HANA_NOT_HPP
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#include <boost/hana/fwd/not.hpp>
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#include <boost/hana/concept/constant.hpp>
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#include <boost/hana/concept/logical.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/to.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/detail/canonical_constant.hpp>
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#include <type_traits>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename X>
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constexpr decltype(auto) not_t::operator()(X&& x) const {
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using Bool = typename hana::tag_of<X>::type;
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using Not = BOOST_HANA_DISPATCH_IF(hana::not_impl<Bool>,
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hana::Logical<Bool>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Logical<Bool>::value,
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"hana::not_(cond) requires 'cond' to be a Logical");
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#endif
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return Not::apply(static_cast<X&&>(x));
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}
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//! @endcond
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template <typename L, bool condition>
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struct not_impl<L, when<condition>> : hana::default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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template <typename L>
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struct not_impl<L, hana::when<std::is_arithmetic<L>::value>> {
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template <typename Cond>
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static constexpr Cond apply(Cond const& cond)
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{ return static_cast<Cond>(cond ? false : true); }
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};
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namespace detail {
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template <typename C, typename X>
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struct constant_from_not {
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static constexpr auto value = hana::not_(hana::value<X>());
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using hana_tag = detail::CanonicalConstant<typename C::value_type>;
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};
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}
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template <typename C>
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struct not_impl<C, hana::when<
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hana::Constant<C>::value &&
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hana::Logical<typename C::value_type>::value
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>> {
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template <typename Cond>
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static constexpr auto apply(Cond const&)
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{ return hana::to<C>(detail::constant_from_not<C, Cond>{}); }
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_NOT_HPP
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