]>
Commit | Line | Data |
---|---|---|
7c673cae FG |
1 | // Copyright David Abrahams 2003. Use, modification and distribution is |
2 | // subject to the Boost Software License, Version 1.0. (See accompanying | |
3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
4 | #ifndef BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_ | |
5 | # define BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_ | |
6 | ||
7 | # include <boost/static_assert.hpp> | |
8 | # include <boost/type_traits/is_convertible.hpp> | |
9 | # include <boost/type_traits/is_same.hpp> | |
10 | ||
11 | # include <boost/mpl/placeholders.hpp> | |
12 | # include <boost/mpl/aux_/lambda_support.hpp> | |
13 | ||
14 | namespace boost { | |
15 | namespace iterators { | |
16 | namespace detail { | |
17 | ||
18 | template <bool GreaterEqual, bool LessEqual> | |
19 | struct minimum_category_impl; | |
20 | ||
21 | template <class T1, class T2> | |
22 | struct error_not_related_by_convertibility; | |
23 | ||
24 | template <> | |
25 | struct minimum_category_impl<true,false> | |
26 | { | |
27 | template <class T1, class T2> struct apply | |
28 | { | |
29 | typedef T2 type; | |
30 | }; | |
31 | }; | |
32 | ||
33 | template <> | |
34 | struct minimum_category_impl<false,true> | |
35 | { | |
36 | template <class T1, class T2> struct apply | |
37 | { | |
38 | typedef T1 type; | |
39 | }; | |
40 | }; | |
41 | ||
42 | template <> | |
43 | struct minimum_category_impl<true,true> | |
44 | { | |
45 | template <class T1, class T2> struct apply | |
46 | { | |
47 | BOOST_STATIC_ASSERT((is_same<T1,T2>::value)); | |
48 | typedef T1 type; | |
49 | }; | |
50 | }; | |
51 | ||
52 | template <> | |
53 | struct minimum_category_impl<false,false> | |
54 | { | |
55 | template <class T1, class T2> struct apply | |
56 | : error_not_related_by_convertibility<T1,T2> | |
57 | { | |
58 | }; | |
59 | }; | |
60 | ||
61 | } // namespace detail | |
62 | ||
63 | // | |
64 | // Returns the minimum category type or fails to compile | |
65 | // if T1 and T2 are unrelated. | |
66 | // | |
67 | template <class T1 = mpl::_1, class T2 = mpl::_2> | |
68 | struct minimum_category | |
69 | { | |
70 | typedef boost::iterators::detail::minimum_category_impl< | |
71 | ::boost::is_convertible<T1,T2>::value | |
72 | , ::boost::is_convertible<T2,T1>::value | |
73 | > outer; | |
74 | ||
75 | typedef typename outer::template apply<T1,T2> inner; | |
76 | typedef typename inner::type type; | |
77 | ||
78 | BOOST_MPL_AUX_LAMBDA_SUPPORT(2,minimum_category,(T1,T2)) | |
79 | }; | |
80 | ||
81 | template <> | |
82 | struct minimum_category<mpl::_1,mpl::_2> | |
83 | { | |
84 | template <class T1, class T2> | |
85 | struct apply : minimum_category<T1,T2> | |
86 | {}; | |
87 | ||
88 | BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2,minimum_category,(mpl::_1,mpl::_2)) | |
89 | }; | |
90 | ||
91 | } // namespace iterators | |
92 | ||
93 | } // namespace boost | |
94 | ||
95 | #endif // BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_ |