//-----------------------------------------------------------------------------

 // boost variant/detail/enable_recursive_fwd.hpp header file

 // See http://www.boost.org for updates, documentation, and revision history.

 //-----------------------------------------------------------------------------

 //

 // Copyright (c) 2003

 // Eric Friedman

 //

 // 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_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP

 #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP

 #include "boost/mpl/aux_/config/ctps.hpp"

 #include "boost/mpl/bool_fwd.hpp"

 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

 #   include "boost/mpl/bool.hpp"

 #else

 #   include "boost/type_traits/is_base_and_derived.hpp"

 #endif

 namespace boost {

 namespace detail { namespace variant {

 ///////////////////////////////////////////////////////////////////////////////

 // (detail) tag recursive_flag

 //

 // Signifies that the variant should perform recursive substituion.

 //

 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

 template <typename T>

 struct recursive_flag

 {

     typedef T type;

 };

 #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

 struct recursive_flag_tag

 {

 };

 template <typename T>

 struct recursive_flag

     : recursive_flag_tag

 {

     typedef T type;

 };

 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround

 ///////////////////////////////////////////////////////////////////////////////

 // (detail) metafunction is_recursive_flag

 //

 // Signifies that the variant should perform recursive substituion.

 //

 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

 template <typename T>

 struct is_recursive_flag

     : mpl::false_

 {

 };

 template <typename T>

 struct is_recursive_flag< recursive_flag<T> >

     : mpl::true_

 {

 };

 #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

 template <typename T>

 struct is_recursive_flag

     : is_base_and_derived< recursive_flag_tag,T >

 {

 };

 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround

 ///////////////////////////////////////////////////////////////////////////////

 // (detail) metafunction enable_recursive

 //

 // Attempts recursive_variant_ tag substitution, wrapping with

 // boost::recursive_wrapper if substituion occurs w/ non-indirect result

 // (i.e., not a reference or pointer) *and* NoWrapper is false_.

 //

 template <

       typename T

     , typename RecursiveVariant

     , typename NoWrapper = mpl::false_

     >

 struct enable_recursive;

 ///////////////////////////////////////////////////////////////////////////////

 // (detail) metafunction class quoted_enable_recursive

 //

 // Same behavior as enable_recursive metafunction (see above).

 //

 template <

       typename RecursiveVariant

     , typename NoWrapper = mpl::false_

     >

 struct quoted_enable_recursive;

 }} // namespace detail::variant

 } // namespace boost

 #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP