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