williamr@2: //
williamr@2: // Boost.Pointer Container
williamr@2: //
williamr@2: //  Copyright Thorsten Ottosen 2003-2005. Use, modification and
williamr@2: //  distribution is subject to the Boost Software License, Version
williamr@2: //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
williamr@2: //  http://www.boost.org/LICENSE_1_0.txt)
williamr@2: //
williamr@2: // For more information, see http://www.boost.org/libs/ptr_container/
williamr@2: //
williamr@2: 
williamr@2: 
williamr@2: #ifndef BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
williamr@2: #define BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
williamr@2: 
williamr@2: #if defined(_MSC_VER) && (_MSC_VER >= 1200)
williamr@2: # pragma once
williamr@2: #endif
williamr@2: 
williamr@2: #include <boost/type_traits/detail/yes_no_type.hpp>
williamr@2: #include <boost/mpl/eval_if.hpp>
williamr@2: #include <boost/mpl/identity.hpp>
williamr@2: #include <boost/config.hpp>
williamr@2: 
williamr@2: namespace boost
williamr@2: {
williamr@2:     
williamr@2:     template< class T >
williamr@2:     struct nullable
williamr@2:     {
williamr@2:         typedef T type;
williamr@2:     };   
williamr@2: 
williamr@2:     namespace ptr_container_detail
williamr@2:     {
williamr@2:         template< class T >
williamr@2:         type_traits::yes_type is_nullable( const nullable<T>* );
williamr@2: 
williamr@2:         type_traits::no_type is_nullable( ... );        
williamr@2:     }
williamr@2: 
williamr@2:     template< class T >
williamr@2:     struct is_nullable
williamr@2:     {
williamr@2:     private:
williamr@2:             BOOST_STATIC_CONSTANT( T*, var );
williamr@2:     public:
williamr@2:             BOOST_STATIC_CONSTANT(bool, value = sizeof( ptr_container_detail::is_nullable( var ) ) 
williamr@2:                                                 == sizeof( type_traits::yes_type ) );
williamr@2:     };
williamr@2:     
williamr@2:     template< class T >
williamr@2:     struct remove_nullable
williamr@2:     {
williamr@2:         typedef BOOST_DEDUCED_TYPENAME mpl::eval_if< is_nullable<T>,
williamr@2:                                                       T,
williamr@2:                                             mpl::identity<T> >::type
williamr@2:             type;
williamr@2:     };
williamr@2: 
williamr@2: }
williamr@2: 
williamr@2: #endif