1 2 #ifndef BOOST_MPL_EMPTY_BASE_HPP_INCLUDED 3 #define BOOST_MPL_EMPTY_BASE_HPP_INCLUDED 4 5 // Copyright Aleksey Gurtovoy 2001-2004 6 // 7 // Distributed under the Boost Software License, Version 1.0. 8 // (See accompanying file LICENSE_1_0.txt or copy at 9 // http://www.boost.org/LICENSE_1_0.txt) 10 // 11 // See http://www.boost.org/libs/mpl for documentation. 12 13 // $Id$ 14 // $Date$ 15 // $Revision$ 16 17 #include <boost/mpl/bool.hpp> 18 #include <boost/mpl/aux_/config/msvc.hpp> 19 #include <boost/mpl/aux_/config/workaround.hpp> 20 #include <boost/mpl/aux_/lambda_support.hpp> 21 22 #include <boost/type_traits/integral_constant.hpp> 23 #include <boost/type_traits/is_empty.hpp> 24 25 namespace boost { namespace mpl { 26 27 // empty base class, guaranteed to have no members; inheritance from 28 // 'empty_base' through the 'inherit' metafunction is a no-op - see 29 // "mpl/inherit.hpp> header for the details 30 struct empty_base {}; 31 32 template< typename T > 33 struct is_empty_base 34 : false_ 35 { 36 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 37 using false_::value; 38 #endif 39 }; 40 41 template<> 42 struct is_empty_base<empty_base> 43 : true_ 44 { 45 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 46 using true_::value; 47 #endif 48 }; 49 50 }} 51 52 namespace boost { 53 54 template<> struct is_empty< mpl::empty_base > 55 : public ::boost::integral_constant<bool,true> 56 { 57 public: 58 BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,is_empty,(mpl::empty_base)) 59 }; 60 61 } 62 63 #endif // BOOST_MPL_EMPTY_BASE_HPP_INCLUDED 64