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
22namespace 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
46 operator()(const It& it) const
47 {
48 return fusion::prior(it);
49 }
50
51 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
52 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
76 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