1 //-----------------------------------------------------------------------------
2 // boost variant/detail/enable_recursive_fwd.hpp header file
3 // See http://www.boost.org for updates, documentation, and revision history.
4 //-----------------------------------------------------------------------------
5 //
6 // Copyright (c) 2003
7 // Eric Friedman
8 //
9 // Distributed under the Boost Software License, Version 1.0. (See
10 // accompanying file LICENSE_1_0.txt or copy at
11 // http://www.boost.org/LICENSE_1_0.txt)
12 
13 #ifndef BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
14 #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
15 
16 #include <boost/mpl/aux_/config/ctps.hpp>
17 
18 #include <boost/mpl/bool_fwd.hpp>
19 
20 #   include <boost/mpl/bool.hpp>
21 
22 namespace boost {
23 namespace detail { namespace variant {
24 
25 ///////////////////////////////////////////////////////////////////////////////
26 // (detail) tag recursive_flag
27 //
28 // Signifies that the variant should perform recursive substituion.
29 //
30 
31 
32 template <typename T>
33 struct recursive_flag
34 {
35     typedef T type;
36 };
37 
38 
39 ///////////////////////////////////////////////////////////////////////////////
40 // (detail) metafunction is_recursive_flag
41 //
42 // Signifies that the variant should perform recursive substituion.
43 //
44 
45 
46 template <typename T>
47 struct is_recursive_flag
48     : mpl::false_
49 {
50 };
51 
52 template <typename T>
53 struct is_recursive_flag< recursive_flag<T> >
54     : mpl::true_
55 {
56 };
57 
58 
59 ///////////////////////////////////////////////////////////////////////////////
60 // (detail) metafunction enable_recursive
61 //
62 // Attempts recursive_variant_ tag substitution, wrapping with
63 // boost::recursive_wrapper if substituion occurs w/ non-indirect result
64 // (i.e., not a reference or pointer) *and* NoWrapper is false_.
65 //
66 template <
67       typename T
68     , typename RecursiveVariant
69     , typename NoWrapper = mpl::false_
70     >
71 struct enable_recursive;
72 
73 ///////////////////////////////////////////////////////////////////////////////
74 // (detail) metafunction class quoted_enable_recursive
75 //
76 // Same behavior as enable_recursive metafunction (see above).
77 //
78 template <
79       typename RecursiveVariant
80     , typename NoWrapper = mpl::false_
81     >
82 struct quoted_enable_recursive;
83 
84 }} // namespace detail::variant
85 } // namespace boost
86 
87 #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_FWD_HPP
88