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diff --git a/boost/hana/plus.hpp b/boost/hana/plus.hpp
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+/*!
+@file
+Defines `boost::hana::plus`.
+
+@copyright Louis Dionne 2013-2016
+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