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1 | // Boost.TypeErasure library |
2 | // | |
3 | // Copyright 2011 Steven Watanabe | |
4 | // | |
5 | // Distributed under the Boost Software License Version 1.0. (See | |
6 | // accompanying file LICENSE_1_0.txt or copy at | |
7 | // http://www.boost.org/LICENSE_1_0.txt) | |
8 | // | |
9 | // $Id$ | |
10 | ||
11 | #ifndef BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED | |
12 | #define BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED | |
13 | ||
14 | namespace boost { | |
15 | namespace type_erasure { | |
16 | ||
11fdf7f2 TL |
17 | #ifndef BOOST_TYPE_ERASURE_DOXYGEN |
18 | ||
7c673cae FG |
19 | template<class Concept, class T> |
20 | class any; | |
21 | ||
22 | template<class Concept, class T> | |
23 | class param; | |
24 | ||
11fdf7f2 TL |
25 | #endif |
26 | ||
7c673cae FG |
27 | /** |
28 | * A metafunction returning the (const/reference qualified) placeholder | |
29 | * corresponding to an @ref any. It will also work for all bases | |
30 | * of @ref any, so it can be applied to the @c Base | |
31 | * parameter of @ref concept_interface. | |
32 | */ | |
33 | template<class T> | |
34 | struct placeholder_of | |
35 | { | |
36 | #ifdef BOOST_TYPE_ERASURE_DOXYGEN | |
37 | typedef detail::unspecified type; | |
38 | #else | |
39 | typedef typename ::boost::type_erasure::placeholder_of< | |
40 | typename T::_boost_type_erasure_derived_type | |
41 | >::type type; | |
42 | #endif | |
43 | }; | |
44 | ||
45 | /** INTERNAL ONLY */ | |
46 | template<class Concept, class T> | |
47 | struct placeholder_of< ::boost::type_erasure::any<Concept, T> > | |
48 | { | |
49 | typedef T type; | |
50 | }; | |
51 | ||
52 | /** INTERNAL ONLY */ | |
53 | template<class Concept, class T> | |
54 | struct placeholder_of< ::boost::type_erasure::param<Concept, T> > | |
55 | { | |
56 | typedef T type; | |
57 | }; | |
58 | ||
11fdf7f2 TL |
59 | #ifndef BOOST_NO_CXX11_TEMPLATE_ALIASES |
60 | ||
61 | template<class T> | |
62 | using placeholder_of_t = typename ::boost::type_erasure::placeholder_of<T>::type; | |
63 | ||
64 | #endif | |
65 | ||
7c673cae FG |
66 | } |
67 | } | |
68 | ||
69 | #endif |