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
22namespace 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
75 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