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
23namespace 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
46 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
54 operator()(Seq const& seq) const
55 {
56 return fusion::begin(seq);
57 }
58
59 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
60 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
84 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