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+
+#ifndef BOOST_CONTRACT_DETAIL_OPTIONAL_HPP_
+#define BOOST_CONTRACT_DETAIL_OPTIONAL_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/optional.hpp>
+#include <boost/type_traits/remove_reference.hpp>
+#include <boost/type_traits/integral_constant.hpp>
+
+namespace boost { namespace contract { namespace detail {
+
+template<typename T>
+struct is_optional : boost::false_type {};
+template<typename T>
+struct is_optional<boost::optional<T> > : boost::true_type {};
+
+template<typename T>
+struct optional_value_type { typedef T type; };
+template<typename T>
+struct optional_value_type<boost::optional<T> > { typedef T type; };
+
+template<typename T>
+struct remove_value_reference_if_optional { typedef T type; };
+template<typename T>
+struct remove_value_reference_if_optional<boost::optional<T> >
+ { typedef typename boost::remove_reference<T>::type type; };
+
+template<typename T>
+T& optional_get(T& x) { return x; }
+template<typename T>
+T& optional_get(boost::optional<T>& x) { return x.get(); }
+template<typename T>
+T& optional_get(boost::optional<T&>& x) { return x.get(); }
+
+} } } // namespace
+
+#endif // #include guard
+