1
2#ifndef BOOST_MPL_VOID_HPP_INCLUDED
3#define BOOST_MPL_VOID_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/void_fwd.hpp>
18#include <boost/mpl/bool.hpp>
19#include <boost/mpl/aux_/na_spec.hpp>
20#include <boost/mpl/aux_/config/msvc.hpp>
21#include <boost/mpl/aux_/config/workaround.hpp>
22
23BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_OPEN
24
25// [JDG Feb-4-2003] made void_ a complete type to allow it to be
26// instantiated so that it can be passed in as an object that can be
27// used to select an overloaded function. Possible use includes signaling
28// a zero arity functor evaluation call.
29struct void_ { typedef void_ type; };
30
31BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_CLOSE
32
33namespace boost { namespace mpl {
34
35template< typename T >
36struct is_void_
37 : false_
38{
39#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
40 using false_::value;
41#endif
42};
43
44template<>
45struct is_void_<void_>
46 : true_
47{
48#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
49 using true_::value;
50#endif
51};
52
53template< typename T >
54struct is_not_void_
55 : true_
56{
57#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
58 using true_::value;
59#endif
60};
61
62template<>
63struct is_not_void_<void_>
64 : false_
65{
66#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
67 using false_::value;
68#endif
69};
70
71BOOST_MPL_AUX_NA_SPEC(1, is_void_)
72BOOST_MPL_AUX_NA_SPEC(1, is_not_void_)
73
74}}
75
76#endif // BOOST_MPL_VOID_HPP_INCLUDED
77