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

// 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