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

// boost variant/detail/enable_recursive.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_HPP

#define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_HPP

#include "boost/variant/detail/enable_recursive_fwd.hpp"

#include "boost/variant/variant_fwd.hpp"

#if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)

#   include "boost/mpl/apply.hpp"

#   include "boost/mpl/eval_if.hpp"

#   include "boost/mpl/lambda.hpp"

#endif

#include "boost/variant/detail/substitute.hpp"

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

#include "boost/mpl/bool_fwd.hpp"

#include "boost/mpl/if.hpp"

#include "boost/mpl/or.hpp"

#include "boost/type_traits/is_pointer.hpp"

#include "boost/type_traits/is_reference.hpp"

#include "boost/type_traits/is_same.hpp"

#include "boost/variant/recursive_wrapper.hpp"

namespace boost {

namespace detail { namespace variant {

#if !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)

#   define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(T,Dest,Source) \

    substitute< T , Dest , Source > \

    /**/

#else // defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)

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

// (detail) class template rebind1

//

// Limited workaround in case 'substitute' metafunction unavailable.

//

template <typename T, typename U1>

struct rebind1

{

private:

    typedef typename mpl::lambda<

          mpl::identity<T>

        >::type le_;

public:

    typedef typename mpl::eval_if<

          is_same< le_, mpl::identity<T> >

        , le_ // identity<T>

        , mpl::apply1<le_, U1>

        >::type type;

};

#   define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(T,Dest,Source) \

    rebind1< T , Dest > \

    /**/

#endif // !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)

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

// (detail) metafunction enable_recursive

//

// See boost/variant/detail/enable_recursive_fwd.hpp for more information.

//

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

template <typename T, typename RecursiveVariant, typename NoWrapper>

struct enable_recursive

    : BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(

          T, RecursiveVariant, ::boost::recursive_variant_

        )

{

};

template <typename T, typename RecursiveVariant>

struct enable_recursive< T,RecursiveVariant,mpl::false_ >

{

private: // helpers, for metafunction result (below)

    typedef typename BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(

          T, RecursiveVariant, ::boost::recursive_variant_

        )::type t_;

public: // metafunction result

    // [Wrap with recursive_wrapper only if rebind really changed something:]

    typedef typename mpl::if_<

          mpl::or_<

              is_same< t_,T >

            , is_reference<t_>

            , is_pointer<t_>

            >

        , t_

        , boost::recursive_wrapper<t_>

        >::type type;

};

#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

template <typename T, typename RecursiveVariant, typename NoWrapper>

struct enable_recursive

{

private: // helpers, for metafunction result (below)

    typedef typename BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(

          T, RecursiveVariant, ::boost::recursive_variant_

        )::type t_;

public: // metafunction result

    // [Wrap with recursive_wrapper only if rebind really changed something:]

    typedef typename mpl::if_<

          mpl::or_<

              NoWrapper

            , is_same< t_,T >

            , is_reference<t_>

            , is_pointer<t_>

            >

        , t_

        , boost::recursive_wrapper<t_>

        >::type type;

};

#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround

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

// (detail) metafunction class quoted_enable_recursive

//

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

//

template <typename RecursiveVariant, typename NoWrapper>

struct quoted_enable_recursive

{

    template <typename T>

    struct apply

        : enable_recursive<T, RecursiveVariant, NoWrapper>

    {

    };

};

}} // namespace detail::variant

} // namespace boost

#endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_HPP