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