1
2#ifndef BOOST_MPL_AUX_NA_HPP_INCLUDED
3#define BOOST_MPL_AUX_NA_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_/na_fwd.hpp>
19#include <boost/mpl/aux_/config/msvc.hpp>
20#include <boost/mpl/aux_/config/ctps.hpp>
21
22namespace boost { namespace mpl {
23
24template< typename T >
25struct is_na
26 : false_
27{
28#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
29 using false_::value;
30#endif
31};
32
33template<>
34struct is_na<na>
35 : true_
36{
37#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
38 using true_::value;
39#endif
40};
41
42template< typename T >
43struct is_not_na
44 : true_
45{
46#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
47 using true_::value;
48#endif
49};
50
51template<>
52struct is_not_na<na>
53 : false_
54{
55#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
56 using false_::value;
57#endif
58};
59
60#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
61template< typename T, typename U > struct if_na
62{
63 typedef T type;
64};
65
66template< typename U > struct if_na<na,U>
67{
68 typedef U type;
69};
70#else
71template< typename T > struct if_na_impl
72{
73 template< typename U > struct apply
74 {
75 typedef T type;
76 };
77};
78
79template<> struct if_na_impl<na>
80{
81 template< typename U > struct apply
82 {
83 typedef U type;
84 };
85};
86
87template< typename T, typename U > struct if_na
88 : if_na_impl<T>::template apply<U>
89{
90};
91#endif
92
93}}
94
95#endif // BOOST_MPL_AUX_NA_HPP_INCLUDED
96

source code of boost/boost/mpl/aux_/na.hpp