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diff --git a/boost/multiprecision/traits/explicit_conversion.hpp b/boost/multiprecision/traits/explicit_conversion.hpp
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+++ b/boost/multiprecision/traits/explicit_conversion.hpp
@@ -0,0 +1,80 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Vicente J. Botet Escriba 2009-2011
+//  Copyright 2012 John Maddock. Distributed under the Boost
+//  Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_MP_EXPLICIT_CONVERTIBLE_HPP
+#define BOOST_MP_EXPLICIT_CONVERTIBLE_HPP
+
+#include <boost/type_traits/is_convertible.hpp>
+#include <boost/utility/declval.hpp>
+
+
+namespace boost{ namespace multiprecision{ namespace detail{
+
+template <int N>
+struct dummy_size{};
+
+template<typename S, typename T>
+struct has_generic_interconversion
+{
+   typedef typename mpl::if_c<
+      is_number<S>::value && is_number<T>::value,
+      typename mpl::if_c<
+         number_category<S>::value == number_kind_integer,
+         typename mpl::if_c<
+            number_category<T>::value == number_kind_integer 
+            || number_category<T>::value == number_kind_floating_point
+            || number_category<T>::value == number_kind_rational
+            || number_category<T>::value == number_kind_fixed_point,
+            mpl::true_, 
+            mpl::false_
+         >::type,
+         typename mpl::if_c<
+            number_category<S>::value == number_kind_rational,
+            typename mpl::if_c<
+               number_category<T>::value == number_kind_rational
+               || number_category<T>::value == number_kind_rational,
+               mpl::true_,
+               mpl::false_
+            >::type,
+            typename mpl::if_c<
+               number_category<T>::value == number_kind_floating_point,
+               mpl::true_,
+               mpl::false_
+            >::type
+         >::type
+      >::type,
+      mpl::false_
+   >::type type;
+};
+
+template<typename S, typename T>
+struct is_explicitly_convertible_imp
+{
+#ifndef BOOST_NO_SFINAE_EXPR
+   template<typename S1, typename T1>
+   static type_traits::yes_type selector(dummy_size<sizeof(static_cast<T1>(declval<S1>()))>*);
+
+   template<typename S1, typename T1>
+   static type_traits::no_type selector(...);
+
+   static const bool value = sizeof(selector<S,T>(0)) == sizeof(type_traits::yes_type);
+
+   typedef boost::integral_constant<bool,value> type;
+#else
+   typedef typename has_generic_interconversion<S, T>::type gen_type;
+   typedef mpl::bool_<boost::is_convertible<S, T>::value || gen_type::value> type;
+#endif
+};
+
+template<typename From, typename To>
+struct is_explicitly_convertible : public is_explicitly_convertible_imp<From, To>::type
+{
+};
+
+}}} // namespaces
+
+#endif
+