1 // Copyright David Abrahams, Daniel Wallin 2003.
2 // Distributed under the Boost Software License, Version 1.0.
3 // (See accompanying file LICENSE_1_0.txt or copy at
4 // http://www.boost.org/LICENSE_1_0.txt)
5 
6 #ifndef BOOST_PARAMETER_AUX_PACK_PREDICATE_HPP
7 #define BOOST_PARAMETER_AUX_PACK_PREDICATE_HPP
8 
9 namespace boost { namespace parameter { namespace aux {
10 
11     // helper for get_predicate<...>, below
12     template <typename T>
13     struct get_predicate_or_default
14     {
15         typedef T type;
16     };
17 
18     // helper for predicate<...>, below
19     template <typename T>
20     struct get_predicate
21       : ::boost::parameter::aux
22         ::get_predicate_or_default<typename T::predicate>
23     {
24     };
25 }}} // namespace boost::parameter::aux
26 
27 #include <boost/parameter/aux_/use_default.hpp>
28 #include <boost/parameter/aux_/always_true_predicate.hpp>
29 
30 namespace boost { namespace parameter { namespace aux {
31 
32     template <>
33     struct get_predicate_or_default< ::boost::parameter::aux::use_default>
34     {
35         typedef ::boost::parameter::aux::always_true_predicate type;
36     };
37 }}} // namespace boost::parameter::aux
38 
39 #include <boost/parameter/required.hpp>
40 #include <boost/parameter/optional.hpp>
41 #include <boost/parameter/config.hpp>
42 
43 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
44 #include <boost/mp11/integral.hpp>
45 #include <boost/mp11/utility.hpp>
46 #else
47 #include <boost/mpl/bool.hpp>
48 #include <boost/mpl/if.hpp>
49 #include <boost/mpl/eval_if.hpp>
50 #include <boost/mpl/identity.hpp>
51 #endif
52 
53 namespace boost { namespace parameter { namespace aux {
54 
55     template <typename T>
56 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
57     using predicate = ::boost::mp11::mp_if<
58         ::boost::mp11::mp_if<
59             ::boost::parameter::aux::is_optional<T>
60           , ::boost::mp11::mp_true
61           , ::boost::parameter::aux::is_required<T>
62         >
63       , ::boost::parameter::aux::get_predicate<T>
64       , ::boost::mp11::mp_identity<
65             ::boost::parameter::aux::always_true_predicate
66         >
67     >;
68 #else
69     struct predicate
70       : ::boost::mpl::eval_if<
71             typename ::boost::mpl::if_<
72                 ::boost::parameter::aux::is_optional<T>
73               , ::boost::mpl::true_
74               , ::boost::parameter::aux::is_required<T>
75             >::type
76           , ::boost::parameter::aux::get_predicate<T>
77           , ::boost::mpl::identity<
78                 ::boost::parameter::aux::always_true_predicate
79             >
80         >
81     {
82     };
83 #endif  // BOOST_PARAMETER_CAN_USE_MP11
84 }}} // namespace boost::parameter::aux
85 
86 #endif  // include guard
87 
88