1 /*=============================================================================
2 Copyright (c) 2001-2011 Joel de Guzman
3 Copyright (c) 2006 Dan Marsden
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
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>
22 namespace boost { namespace fusion {
24 struct zip_view_iterator_tag;
30 template<typename Sig>
34 struct result<poly_prior(It)>
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;
44 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
45 typename result<poly_prior(It)>::type
46 operator()(const It& it) const
48 return fusion::prior(it);
51 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
52 unused_type operator()(unused_type const&) const
61 template<typename Tag>
65 struct prior_impl<zip_view_iterator_tag>
67 template<typename Iterator>
70 typedef zip_view_iterator<
71 typename result_of::transform<typename Iterator::iterators, detail::poly_prior>::type,
72 typename Iterator::category> type;
74 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
76 call(Iterator const& it)
80 fusion::transform(it.iterators_, detail::poly_prior()));