1 /* Copyright 2003-2013 Joaquin M Lopez Munoz.
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  * See http://www.boost.org/libs/multi_index for library home page.
7  */
8 
9 #ifndef BOOST_MULTI_INDEX_DETAIL_ORD_INDEX_ARGS_HPP
10 #define BOOST_MULTI_INDEX_DETAIL_ORD_INDEX_ARGS_HPP
11 
12 #if defined(_MSC_VER)
13 #pragma once
14 #endif
15 
16 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
17 #include <boost/mpl/aux_/na.hpp>
18 #include <boost/mpl/eval_if.hpp>
19 #include <boost/mpl/identity.hpp>
20 #include <boost/mpl/if.hpp>
21 #include <boost/multi_index/tag.hpp>
22 #include <boost/static_assert.hpp>
23 #include <boost/type_traits/is_same.hpp>
24 #include <functional>
25 
26 namespace boost{
27 
28 namespace multi_index{
29 
30 namespace detail{
31 
32 /* Oredered index specifiers can be instantiated in two forms:
33  *
34  *   (ordered_unique|ordered_non_unique)<
35  *     KeyFromValue,Compare=std::less<KeyFromValue::result_type> >
36  *   (ordered_unique|ordered_non_unique)<
37  *     TagList,KeyFromValue,Compare=std::less<KeyFromValue::result_type> >
38  *
39  * index_args implements the machinery to accept this argument-dependent
40  * polymorphism.
41  */
42 
43 template<typename KeyFromValue>
44 struct index_args_default_compare
45 {
46   typedef std::less<typename KeyFromValue::result_type> type;
47 };
48 
49 template<typename Arg1,typename Arg2,typename Arg3>
50 struct ordered_index_args
51 {
52   typedef is_tag<Arg1> full_form;
53 
54   typedef typename mpl::if_<
55     full_form,
56     Arg1,
57     tag< > >::type                                   tag_list_type;
58   typedef typename mpl::if_<
59     full_form,
60     Arg2,
61     Arg1>::type                                      key_from_value_type;
62   typedef typename mpl::if_<
63     full_form,
64     Arg3,
65     Arg2>::type                                      supplied_compare_type;
66   typedef typename mpl::eval_if<
67     mpl::is_na<supplied_compare_type>,
68     index_args_default_compare<key_from_value_type>,
69     mpl::identity<supplied_compare_type>
70   >::type                                            compare_type;
71 
72   BOOST_STATIC_ASSERT(is_tag<tag_list_type>::value);
73   BOOST_STATIC_ASSERT(!mpl::is_na<key_from_value_type>::value);
74   BOOST_STATIC_ASSERT(!mpl::is_na<compare_type>::value);
75 };
76 
77 } /* namespace multi_index::detail */
78 
79 } /* namespace multi_index */
80 
81 } /* namespace boost */
82 
83 #endif
84