

#ifndef BOOST_MPL_AUX_NA_HPP_INCLUDED

#define BOOST_MPL_AUX_NA_HPP_INCLUDED



// Copyright Aleksey Gurtovoy 2001-2004

//

// 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)

//

// See http://www.boost.org/libs/mpl for documentation.



// $Source$

// $Date: 2004-11-27 20:39:23 -0500 (Sat, 27 Nov 2004) $

// $Revision: 26324 $



#include <boost/mpl/bool.hpp>

#include <boost/mpl/aux_/na_fwd.hpp>

#include <boost/mpl/aux_/config/msvc.hpp>

#include <boost/mpl/aux_/config/ctps.hpp>



namespace boost { namespace mpl {



template< typename T >

struct is_na

    : false_

{

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

    using false_::value;

#endif

};



template<>

struct is_na<na>

    : true_

{

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

    using true_::value;

#endif

};



template< typename T >

struct is_not_na

    : true_

{

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

    using true_::value;

#endif

};



template<>

struct is_not_na<na>

    : false_

{

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

    using false_::value;

#endif

};



#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

template< typename T, typename U > struct if_na

{

    typedef T type;

};



template< typename U > struct if_na<na,U>

{

    typedef U type;

};

#else

template< typename T > struct if_na_impl

{

    template< typename U > struct apply

    {

        typedef T type;

    };

};



template<> struct if_na_impl<na>

{

    template< typename U > struct apply

    {

        typedef U type;

    };

};



template< typename T, typename U > struct if_na

    : if_na_impl<T>::template apply<U>

{

};

#endif



}}



#endif // BOOST_MPL_AUX_NA_HPP_INCLUDED

