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_VALUE_OF_IMPL_20060124_2147)
9#define FUSION_VALUE_OF_IMPL_20060124_2147
10
11#include <boost/fusion/support/config.hpp>
12#include <boost/fusion/container/vector/convert.hpp>
13#include <boost/fusion/algorithm/transformation/transform.hpp>
14#include <boost/fusion/iterator/value_of.hpp>
15#include <boost/mpl/placeholders.hpp>
16#include <boost/fusion/support/unused.hpp>
17#include <boost/mpl/eval_if.hpp>
18#include <boost/mpl/identity.hpp>
19#include <boost/type_traits/is_same.hpp>
20#include <boost/config.hpp>
21
22namespace boost { namespace fusion
23{
24 struct zip_view_iterator_tag;
25
26 namespace detail
27 {
28 struct poly_value_of
29 {
30 template<typename T>
31 struct result;
32
33 template<typename It>
34 struct result<poly_value_of(It)>
35 : mpl::eval_if<is_same<It, unused_type>,
36 mpl::identity<unused_type>,
37 result_of::value_of<It> >
38 {};
39
40 // never called, but needed for decltype-based result_of (C++0x)
41#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
42 template<typename It>
43 BOOST_FUSION_GPU_ENABLED
44 typename result<poly_value_of(It)>::type
45 operator()(It&&) const;
46#endif
47 };
48 }
49
50 namespace extension
51 {
52 template<typename Tag>
53 struct value_of_impl;
54
55 template<>
56 struct value_of_impl<zip_view_iterator_tag>
57 {
58 template<typename Iterator>
59 struct apply
60 {
61 typedef typename result_of::transform<
62 typename Iterator::iterators,
63 detail::poly_value_of>::type values;
64
65 typedef typename result_of::as_vector<values>::type type;
66 };
67 };
68 }
69}}
70
71#endif
72