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+//  (C) Copyright 2009-2011 Frederic Bron, Robert Stewart, Steven Watanabe & Roman Perepelitsa.
+//
+//  Use, modification and distribution are subject to 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).
+//
+//  See http://www.boost.org/libs/type_traits for most recent version including documentation.
+
+#include <boost/config.hpp>
+#include <boost/type_traits/detail/yes_no_type.hpp>
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/type_traits/is_const.hpp>
+#include <boost/type_traits/is_fundamental.hpp>
+#include <boost/type_traits/is_pointer.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/is_void.hpp>
+#include <boost/type_traits/remove_cv.hpp>
+#include <boost/type_traits/remove_pointer.hpp>
+#include <boost/type_traits/remove_reference.hpp>
+
+// avoid warnings
+#if defined(__GNUC__)
+#   pragma GCC system_header
+#elif defined(BOOST_MSVC)
+#   pragma warning ( push )
+#   pragma warning ( disable : 4244 4913)
+#   if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000)
+#       pragma warning ( disable : 6334)
+#   endif
+#endif
+
+namespace boost {
+namespace detail {
+
+// This namespace ensures that argument-dependent name lookup does not mess things up.
+namespace BOOST_JOIN(BOOST_TT_TRAIT_NAME,_impl) {
+
+// 1. a function to have an instance of type T without requiring T to be default
+// constructible
+template <typename T> T &make();
+
+
+// 2. we provide our operator definition for types that do not have one already
+
+// a type returned from operator BOOST_TT_TRAIT_OP when no such operator is
+// found in the type's own namespace (our own operator is used) so that we have
+// a means to know that our operator was used
+struct no_operator { };
+
+// this class allows implicit conversions and makes the following operator
+// definition less-preferred than any other such operators that might be found
+// via argument-dependent name lookup
+struct any { template <class T> any(T const&); };
+
+// when operator BOOST_TT_TRAIT_OP is not available, this one is used
+no_operator operator BOOST_TT_TRAIT_OP (const any&, int);
+
+
+// 3. checks if the operator returns void or not
+// conditions: Lhs!=void
+
+// we first redefine "operator," so that we have no compilation error if
+// operator BOOST_TT_TRAIT_OP returns void and we can use the return type of
+// (lhs BOOST_TT_TRAIT_OP, returns_void_t()) to deduce if
+// operator BOOST_TT_TRAIT_OP returns void or not:
+// - operator BOOST_TT_TRAIT_OP returns void   -> (lhs BOOST_TT_TRAIT_OP, returns_void_t()) returns returns_void_t
+// - operator BOOST_TT_TRAIT_OP returns !=void -> (lhs BOOST_TT_TRAIT_OP, returns_void_t()) returns int
+struct returns_void_t { };
+template <typename T> int operator,(const T&, returns_void_t);
+template <typename T> int operator,(const volatile T&, returns_void_t);
+
+// this intermediate trait has member value of type bool:
+// - value==true -> operator BOOST_TT_TRAIT_OP returns void
+// - value==false -> operator BOOST_TT_TRAIT_OP does not return void
+template < typename Lhs >
+struct operator_returns_void {
+   // overloads of function returns_void make the difference
+   // yes_type and no_type have different size by construction
+   static ::boost::type_traits::yes_type returns_void(returns_void_t);
+   static ::boost::type_traits::no_type returns_void(int);
+   BOOST_STATIC_CONSTANT(bool, value = (sizeof(::boost::type_traits::yes_type)==sizeof(returns_void((make<Lhs>() BOOST_TT_TRAIT_OP,returns_void_t())))));
+};
+
+
+// 4. checks if the return type is Ret or Ret==dont_care
+// conditions: Lhs!=void
+
+struct dont_care { };
+
+template < typename Lhs, typename Ret, bool Returns_void >
+struct operator_returns_Ret;
+
+template < typename Lhs >
+struct operator_returns_Ret < Lhs, dont_care, true > {
+   BOOST_STATIC_CONSTANT(bool, value = true);
+};
+
+template < typename Lhs >
+struct operator_returns_Ret < Lhs, dont_care, false > {
+   BOOST_STATIC_CONSTANT(bool, value = true);
+};
+
+template < typename Lhs >
+struct operator_returns_Ret < Lhs, void, true > {
+   BOOST_STATIC_CONSTANT(bool, value = true);
+};
+
+template < typename Lhs >
+struct operator_returns_Ret < Lhs, void, false > {
+   BOOST_STATIC_CONSTANT(bool, value = false);
+};
+
+template < typename Lhs, typename Ret >
+struct operator_returns_Ret < Lhs, Ret, true > {
+   BOOST_STATIC_CONSTANT(bool, value = false);
+};
+
+// otherwise checks if it is convertible to Ret using the sizeof trick
+// based on overload resolution
+// condition: Ret!=void and Ret!=dont_care and the operator does not return void
+template < typename Lhs, typename Ret >
+struct operator_returns_Ret < Lhs, Ret, false > {
+   static ::boost::type_traits::yes_type is_convertible_to_Ret(Ret); // this version is preferred for types convertible to Ret
+   static ::boost::type_traits::no_type is_convertible_to_Ret(...); // this version is used otherwise
+
+   BOOST_STATIC_CONSTANT(bool, value = (sizeof(is_convertible_to_Ret(make<Lhs>() BOOST_TT_TRAIT_OP))==sizeof(::boost::type_traits::yes_type)));
+};
+
+
+// 5. checks for operator existence
+// condition: Lhs!=void
+
+// checks if our definition of operator BOOST_TT_TRAIT_OP is used or an other
+// existing one;
+// this is done with redefinition of "operator," that returns no_operator or has_operator
+struct has_operator { };
+no_operator operator,(no_operator, has_operator);
+
+template < typename Lhs >
+struct operator_exists {
+   static ::boost::type_traits::yes_type s_check(has_operator); // this version is preferred when operator exists
+   static ::boost::type_traits::no_type s_check(no_operator); // this version is used otherwise
+
+   BOOST_STATIC_CONSTANT(bool, value = (sizeof(s_check(((make<Lhs>() BOOST_TT_TRAIT_OP),make<has_operator>())))==sizeof(::boost::type_traits::yes_type)));
+};
+
+
+// 6. main trait: to avoid any compilation error, this class behaves
+// differently when operator BOOST_TT_TRAIT_OP(Lhs) is forbidden by the
+// standard.
+// Forbidden_if is a bool that is:
+// - true when the operator BOOST_TT_TRAIT_OP(Lhs) is forbidden by the standard
+//   (would yield compilation error if used)
+// - false otherwise
+template < typename Lhs, typename Ret, bool Forbidden_if >
+struct trait_impl1;
+
+template < typename Lhs, typename Ret >
+struct trait_impl1 < Lhs, Ret, true > {
+   BOOST_STATIC_CONSTANT(bool, value = false);
+};
+
+template < typename Lhs, typename Ret >
+struct trait_impl1 < Lhs, Ret, false > {
+   BOOST_STATIC_CONSTANT(bool,
+      value = (operator_exists < Lhs >::value && operator_returns_Ret < Lhs, Ret, operator_returns_void < Lhs >::value >::value));
+};
+
+// specialization needs to be declared for the special void case
+template < typename Ret >
+struct trait_impl1 < void, Ret, false > {
+   BOOST_STATIC_CONSTANT(bool, value = false);
+};
+
+// defines some typedef for convenience
+template < typename Lhs, typename Ret >
+struct trait_impl {
+   typedef typename ::boost::remove_reference<Lhs>::type Lhs_noref;
+   typedef typename ::boost::remove_cv<Lhs_noref>::type Lhs_nocv;
+   typedef typename ::boost::remove_cv< typename ::boost::remove_reference< typename ::boost::remove_pointer<Lhs_noref>::type >::type >::type Lhs_noptr;
+   BOOST_STATIC_CONSTANT(bool, value = (trait_impl1 < Lhs_noref, Ret, BOOST_TT_FORBIDDEN_IF >::value));
+};
+
+} // namespace impl
+} // namespace detail
+
+// this is the accessible definition of the trait to end user
+template <class Lhs, class Ret=::boost::detail::BOOST_JOIN(BOOST_TT_TRAIT_NAME,_impl)::dont_care>
+struct BOOST_TT_TRAIT_NAME : public integral_constant<bool, (::boost::detail::BOOST_JOIN(BOOST_TT_TRAIT_NAME, _impl)::trait_impl< Lhs, Ret >::value)>{};
+
+} // namespace boost
+
+#if defined(BOOST_MSVC)
+#   pragma warning ( pop )
+#endif