sl@0: //
sl@0: // Boost.Pointer Container
sl@0: //
sl@0: //  Copyright Thorsten Ottosen 2003-2005. Use, modification and
sl@0: //  distribution is subject to the Boost Software License, Version
sl@0: //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
sl@0: //  http://www.boost.org/LICENSE_1_0.txt)
sl@0: //
sl@0: // For more information, see http://www.boost.org/libs/ptr_container/
sl@0: //
sl@0: 
sl@0: 
sl@0: #ifndef BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
sl@0: #define BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
sl@0: 
sl@0: #if defined(_MSC_VER) && (_MSC_VER >= 1200)
sl@0: # pragma once
sl@0: #endif
sl@0: 
sl@0: #include <boost/type_traits/detail/yes_no_type.hpp>
sl@0: #include <boost/mpl/eval_if.hpp>
sl@0: #include <boost/mpl/identity.hpp>
sl@0: #include <boost/config.hpp>
sl@0: 
sl@0: namespace boost
sl@0: {
sl@0:     
sl@0:     template< class T >
sl@0:     struct nullable
sl@0:     {
sl@0:         typedef T type;
sl@0:     };   
sl@0: 
sl@0:     namespace ptr_container_detail
sl@0:     {
sl@0:         template< class T >
sl@0:         type_traits::yes_type is_nullable( const nullable<T>* );
sl@0: 
sl@0:         type_traits::no_type is_nullable( ... );        
sl@0:     }
sl@0: 
sl@0:     template< class T >
sl@0:     struct is_nullable
sl@0:     {
sl@0:     private:
sl@0:             BOOST_STATIC_CONSTANT( T*, var );
sl@0:     public:
sl@0:             BOOST_STATIC_CONSTANT(bool, value = sizeof( ptr_container_detail::is_nullable( var ) ) 
sl@0:                                                 == sizeof( type_traits::yes_type ) );
sl@0:     };
sl@0:     
sl@0:     template< class T >
sl@0:     struct remove_nullable
sl@0:     {
sl@0:         typedef BOOST_DEDUCED_TYPENAME mpl::eval_if< is_nullable<T>,
sl@0:                                                       T,
sl@0:                                             mpl::identity<T> >::type
sl@0:             type;
sl@0:     };
sl@0: 
sl@0: }
sl@0: 
sl@0: #endif