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_BEGIN_IMPL_20060123_2147)
9 #define FUSION_BEGIN_IMPL_20060123_2147
10 
11 #include <boost/fusion/support/config.hpp>
12 #include <boost/fusion/sequence/intrinsic/begin.hpp>
13 #include <boost/fusion/view/zip_view/zip_view_iterator_fwd.hpp>
14 #include <boost/fusion/algorithm/transformation/transform.hpp>
15 #include <boost/type_traits/remove_reference.hpp>
16 #include <boost/type_traits/is_reference.hpp>
17 #include <boost/type_traits/is_same.hpp>
18 #include <boost/mpl/assert.hpp>
19 #include <boost/mpl/eval_if.hpp>
20 #include <boost/mpl/identity.hpp>
21 #include <boost/fusion/support/unused.hpp>
22 
23 namespace boost { namespace fusion {
24 
25     struct zip_view_tag;
26 
27     namespace detail
28     {
29         struct poly_begin
30         {
31             template<typename T>
32             struct result;
33 
34             template<typename SeqRef>
35             struct result<poly_begin(SeqRef)>
36                 : mpl::eval_if<is_same<SeqRef, unused_type const&>,
37                                mpl::identity<unused_type>,
38                                result_of::begin<typename remove_reference<SeqRef>::type> >
39             {
40                 BOOST_MPL_ASSERT((is_reference<SeqRef>));
41             };
42 
43             template<typename Seq>
44             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
45             typename result<poly_begin(Seq&)>::type
operator ()boost::fusion::detail::poly_begin46             operator()(Seq& seq) const
47             {
48                 return fusion::begin(seq);
49             }
50 
51             template<typename Seq>
52             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
53             typename result<poly_begin(Seq const&)>::type
operator ()boost::fusion::detail::poly_begin54             operator()(Seq const& seq) const
55             {
56                 return fusion::begin(seq);
57             }
58 
59             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
operator ()boost::fusion::detail::poly_begin60             unused_type operator()(unused_type const&) const
61             {
62                 return unused_type();
63             }
64         };
65     }
66 
67     namespace extension
68     {
69         template<typename Tag>
70         struct begin_impl;
71 
72         template<>
73         struct begin_impl<zip_view_tag>
74         {
75             template<typename Sequence>
76             struct apply
77             {
78                 typedef zip_view_iterator<
79                     typename result_of::transform<typename Sequence::sequences, detail::poly_begin>::type,
80                     typename Sequence::category> type;
81 
82                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
83                 static type
callboost::fusion::extension::begin_impl::apply84                 call(Sequence& sequence)
85                 {
86                     return type(
87                         fusion::transform(sequence.sequences_, detail::poly_begin()));
88                 }
89             };
90 
91 
92 
93         };
94     }
95 }}
96 
97 #endif
98