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_PRIOR_IMPL_20060124_2006)
9 #define FUSION_PRIOR_IMPL_20060124_2006
10 
11 #include <boost/fusion/support/config.hpp>
12 #include <boost/fusion/view/zip_view/zip_view_iterator_fwd.hpp>
13 #include <boost/fusion/iterator/prior.hpp>
14 #include <boost/fusion/algorithm/transformation/transform.hpp>
15 #include <boost/fusion/support/unused.hpp>
16 #include <boost/mpl/eval_if.hpp>
17 #include <boost/mpl/identity.hpp>
18 #include <boost/type_traits/is_same.hpp>
19 #include <boost/type_traits/remove_reference.hpp>
20 #include <boost/type_traits/remove_const.hpp>
21 
22 namespace boost { namespace fusion {
23 
24     struct zip_view_iterator_tag;
25 
26     namespace detail
27     {
28         struct poly_prior
29         {
30             template<typename Sig>
31             struct result;
32 
33             template<typename It>
34             struct result<poly_prior(It)>
35             {
36                 typedef typename remove_const<
37                     typename remove_reference<It>::type>::type it;
38                 typedef typename mpl::eval_if<is_same<it, unused_type>,
39                     mpl::identity<unused_type>,
40                     result_of::prior<it> >::type type;
41             };
42 
43             template<typename It>
44             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
45             typename result<poly_prior(It)>::type
operator ()boost::fusion::detail::poly_prior46             operator()(const It& it) const
47             {
48                 return fusion::prior(it);
49             }
50 
51             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
operator ()boost::fusion::detail::poly_prior52             unused_type operator()(unused_type const&) const
53             {
54                 return unused_type();
55             }
56         };
57     }
58 
59     namespace extension
60     {
61         template<typename Tag>
62         struct prior_impl;
63 
64         template<>
65         struct prior_impl<zip_view_iterator_tag>
66         {
67             template<typename Iterator>
68             struct apply
69             {
70                 typedef zip_view_iterator<
71                     typename result_of::transform<typename Iterator::iterators, detail::poly_prior>::type,
72                     typename Iterator::category> type;
73 
74                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
75                 static type
callboost::fusion::extension::prior_impl::apply76                 call(Iterator const& it)
77 
78                 {
79                     return type(
80                         fusion::transform(it.iterators_, detail::poly_prior()));
81                 }
82             };
83         };
84     }
85 }}
86 
87 #endif
88