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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 |