1 | |
2 | #ifndef BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED |
3 | #define BOOST_MPL_IS_PLACEHOLDER_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/arg_fwd.hpp> |
18 | #include <boost/mpl/bool.hpp> |
19 | #include <boost/mpl/aux_/yes_no.hpp> |
20 | #include <boost/mpl/aux_/type_wrapper.hpp> |
21 | #include <boost/mpl/aux_/nttp_decl.hpp> |
22 | #include <boost/mpl/aux_/config/ctps.hpp> |
23 | #include <boost/mpl/aux_/config/static_constant.hpp> |
24 | |
25 | namespace boost { namespace mpl { |
26 | |
27 | #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
28 | |
29 | template< typename T > |
30 | struct is_placeholder |
31 | : bool_<false> |
32 | { |
33 | }; |
34 | |
35 | template< BOOST_MPL_AUX_NTTP_DECL(int, N) > |
36 | struct is_placeholder< arg<N> > |
37 | : bool_<true> |
38 | { |
39 | }; |
40 | |
41 | #else |
42 | |
43 | namespace aux { |
44 | |
45 | aux::no_tag is_placeholder_helper(...); |
46 | |
47 | template< BOOST_MPL_AUX_NTTP_DECL(int, N) > |
48 | aux::yes_tag is_placeholder_helper(aux::type_wrapper< arg<N> >*); |
49 | |
50 | } // namespace aux |
51 | |
52 | template< typename T > |
53 | struct is_placeholder |
54 | { |
55 | static aux::type_wrapper<T>* get(); |
56 | BOOST_STATIC_CONSTANT(bool, value = |
57 | sizeof(aux::is_placeholder_helper(get())) == sizeof(aux::yes_tag) |
58 | ); |
59 | |
60 | typedef bool_<value> type; |
61 | }; |
62 | |
63 | #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
64 | |
65 | }} |
66 | |
67 | #endif // BOOST_MPL_IS_PLACEHOLDER_HPP_INCLUDED |
68 | |