1 /*=============================================================================
2     Copyright (c) 2001-2011 Joel de Guzman
3     Copyright (c) 2006 Dan Marsden
4 
5     Distributed under the Boost Software License, Version 1.0. (See accompanying
6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 ==============================================================================*/
8 #if !defined(FUSION_DISTANCE_IMPL_20060124_2033)
9 #define FUSION_DISTANCE_IMPL_20060124_2033
10 
11 #include <boost/fusion/support/config.hpp>
12 #include <boost/mpl/eval_if.hpp>
13 #include <boost/mpl/placeholders.hpp>
14 #include <boost/mpl/assert.hpp>
15 #include <boost/fusion/iterator/distance.hpp>
16 #include <boost/fusion/support/category_of.hpp>
17 #include <boost/fusion/algorithm/query/find_if.hpp>
18 #include <boost/fusion/sequence/intrinsic/end.hpp>
19 #include <boost/fusion/sequence/intrinsic/value_at.hpp>
20 #include <boost/type_traits/is_same.hpp>
21 
22 namespace boost { namespace fusion {
23 
24     struct zip_view_iterator_tag;
25 
26     struct random_access_iterator_tag;
27 
28     namespace detail
29     {
30         template<typename FoundIt, typename SearchIt>
31         struct best_distance
32         {
33             typedef typename result_of::find_if<
34                 typename SearchIt::iterators, is_same<traits::category_of<mpl::_>, random_access_iterator_tag> > finder;
35 
36             BOOST_MPL_ASSERT_NOT((is_same<typename finder::type, result_of::end<typename SearchIt::iterators> >));
37 
38             typedef typename result_of::distance<FoundIt, typename finder::type>::type type;
39         };
40 
41         template<typename It1, typename It2>
42         struct default_distance
43             : result_of::distance<
44             typename result_of::value_at_c<typename It1::iterators, 0>::type,
45             typename result_of::value_at_c<typename It2::iterators, 0>::type>
46         {};
47 
48         template<typename It1, typename It2>
49         struct zip_view_iterator_distance
50         {
51             typedef typename result_of::find_if<
52                 typename It1::iterators, is_same<traits::category_of<mpl::_>, random_access_iterator_tag> > finder;
53 
54             typedef typename mpl::eval_if<
55                 is_same<typename finder::type, typename result_of::end<typename It1::iterators>::type>,
56                 detail::default_distance<It1, It2> ,
57                 detail::best_distance<typename finder::type, It2> >::type type;
58         };
59     }
60 
61     namespace extension
62     {
63         template<typename Tag>
64         struct distance_impl;
65 
66         template<>
67         struct distance_impl<zip_view_iterator_tag>
68         {
69             template<typename It1, typename It2>
70             struct apply
71                 : detail::zip_view_iterator_distance<It1, It2>::type
72             {
73                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
74                 static typename detail::zip_view_iterator_distance<It1, It2>::type
callboost::fusion::extension::distance_impl::apply75                 call(It1 const& /*it1*/, It2 const& /*it2*/)
76                 {
77                     return typename detail::zip_view_iterator_distance<It1, It2>::type();
78                 }
79             };
80         };
81     }
82 }}
83 
84 #endif
85