62 lines
1.9 KiB
C++
62 lines
1.9 KiB
C++
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/*!
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@file
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Defines `boost::hana::negate`.
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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_NEGATE_HPP
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#define BOOST_HANA_NEGATE_HPP
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#include <boost/hana/fwd/negate.hpp>
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#include <boost/hana/concept/group.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/fwd/minus.hpp>
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#include <boost/hana/zero.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) negate_t::operator()(X&& x) const {
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using G = typename hana::tag_of<X>::type;
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using Negate = BOOST_HANA_DISPATCH_IF(negate_impl<G>,
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hana::Group<G>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Group<G>::value,
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"hana::negate(x) requires 'x' to be in a Group");
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#endif
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return Negate::apply(static_cast<X&&>(x));
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}
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//! @endcond
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template <typename T, bool condition>
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struct negate_impl<T, when<condition>> : default_ {
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template <typename X>
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static constexpr decltype(auto) apply(X&& x)
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{ return hana::minus(hana::zero<T>(), static_cast<X&&>(x)); }
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};
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//////////////////////////////////////////////////////////////////////////
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// Model for arithmetic data types
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//////////////////////////////////////////////////////////////////////////
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template <typename T>
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struct negate_impl<T, when<std::is_arithmetic<T>::value &&
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!std::is_same<bool, T>::value>> {
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template <typename X>
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static constexpr decltype(auto) apply(X&& x)
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{ return -static_cast<X&&>(x); }
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_NEGATE_HPP
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