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110 lines
3.8 KiB
C++
110 lines
3.8 KiB
C++
/*!
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@file
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Defines `boost::hana::plus`.
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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_PLUS_HPP
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#define BOOST_HANA_PLUS_HPP
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#include <boost/hana/fwd/plus.hpp>
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#include <boost/hana/concept/constant.hpp>
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#include <boost/hana/concept/monoid.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/common.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 <boost/hana/detail/has_common_embedding.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, typename Y>
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constexpr decltype(auto) plus_t::operator()(X&& x, Y&& y) const {
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using T = typename hana::tag_of<X>::type;
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using U = typename hana::tag_of<Y>::type;
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using Plus = BOOST_HANA_DISPATCH_IF(decltype(plus_impl<T, U>{}),
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hana::Monoid<T>::value &&
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hana::Monoid<U>::value &&
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!is_default<plus_impl<T, U>>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Monoid<T>::value,
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"hana::plus(x, y) requires 'x' to be a Monoid");
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static_assert(hana::Monoid<U>::value,
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"hana::plus(x, y) requires 'y' to be a Monoid");
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static_assert(!is_default<plus_impl<T, U>>::value,
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"hana::plus(x, y) requires 'x' and 'y' to be embeddable "
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"in a common Monoid");
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#endif
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return Plus::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
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}
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//! @endcond
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template <typename T, typename U, bool condition>
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struct plus_impl<T, U, when<condition>> : 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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// Cross-type overload
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template <typename T, typename U>
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struct plus_impl<T, U, when<
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detail::has_nontrivial_common_embedding<Monoid, T, U>::value
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>> {
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using C = typename common<T, U>::type;
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template <typename X, typename Y>
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static constexpr decltype(auto) apply(X&& x, Y&& y) {
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return hana::plus(hana::to<C>(static_cast<X&&>(x)),
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hana::to<C>(static_cast<Y&&>(y)));
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}
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};
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//////////////////////////////////////////////////////////////////////////
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// Model for non-boolean arithmetic data types
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//////////////////////////////////////////////////////////////////////////
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template <typename T>
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struct plus_impl<T, T, when<
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std::is_arithmetic<T>::value &&
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!std::is_same<T, bool>::value
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>> {
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template <typename X, typename Y>
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static constexpr decltype(auto) apply(X&& x, Y&& y)
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{ return static_cast<X&&>(x) + static_cast<Y&&>(y); }
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};
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//////////////////////////////////////////////////////////////////////////
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// Model for Constants over a Monoid
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//////////////////////////////////////////////////////////////////////////
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namespace detail {
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template <typename C, typename X, typename Y>
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struct constant_from_plus {
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static constexpr auto value = hana::plus(hana::value<X>(), hana::value<Y>());
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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 plus_impl<C, C, when<
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hana::Constant<C>::value &&
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Monoid<typename C::value_type>::value
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>> {
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template <typename X, typename Y>
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static constexpr decltype(auto) apply(X const&, Y const&)
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{ return hana::to<C>(detail::constant_from_plus<C, X, Y>{}); }
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_PLUS_HPP
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