//

// Boost.Pointer Container

//

//  Copyright Thorsten Ottosen 2003-2005. Use, modification and

//  distribution is 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)

//

// For more information, see http://www.boost.org/libs/ptr_container/

//

#ifndef BOOST_INDIRECT_CONTAINER_NULLABLE_HPP

#define BOOST_INDIRECT_CONTAINER_NULLABLE_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)

# pragma once

#endif

#include <boost/type_traits/detail/yes_no_type.hpp>

#include <boost/mpl/eval_if.hpp>

#include <boost/mpl/identity.hpp>

#include <boost/config.hpp>

namespace boost

{

    template< class T >

    struct nullable

    {

        typedef T type;

    };   

    namespace ptr_container_detail

    {

        template< class T >

        type_traits::yes_type is_nullable( const nullable<T>* );

        type_traits::no_type is_nullable( ... );        

    }

    template< class T >

    struct is_nullable

    {

    private:

            BOOST_STATIC_CONSTANT( T*, var );

    public:

            BOOST_STATIC_CONSTANT(bool, value = sizeof( ptr_container_detail::is_nullable( var ) ) 

                                                == sizeof( type_traits::yes_type ) );

    };

    template< class T >

    struct remove_nullable

    {

        typedef BOOST_DEDUCED_TYPENAME mpl::eval_if< is_nullable<T>,

                                                      T,

                                            mpl::identity<T> >::type

            type;

    };

}

#endif