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1 | #ifndef BOOST_METAPARSE_V1_IMPL_NTH_OF_C_IMPL_HPP |
2 | #define BOOST_METAPARSE_V1_IMPL_NTH_OF_C_IMPL_HPP | |
3 | ||
4 | // Copyright Abel Sinkovics (abel@sinkovics.hu) 2013. | |
5 | // Distributed under the Boost Software License, Version 1.0. | |
6 | // (See accompanying file LICENSE_1_0.txt or copy at | |
7 | // http://www.boost.org/LICENSE_1_0.txt) | |
8 | ||
9 | #include <boost/metaparse/v1/impl/skip_seq.hpp> | |
10 | ||
11 | #include <boost/mpl/front.hpp> | |
12 | #include <boost/mpl/pop_front.hpp> | |
13 | #include <boost/mpl/fold.hpp> | |
14 | ||
15 | namespace boost | |
16 | { | |
17 | namespace metaparse | |
18 | { | |
19 | namespace v1 | |
20 | { | |
21 | namespace impl | |
22 | { | |
23 | template <int N, class Seq> | |
24 | struct nth_of_c_impl | |
25 | { | |
26 | private: | |
27 | template <class NextResult> | |
28 | struct apply_unchecked : | |
29 | nth_of_c_impl< | |
30 | N - 1, | |
31 | typename boost::mpl::pop_front<Seq>::type | |
32 | >::template apply< | |
33 | typename get_remaining<NextResult>::type, | |
34 | typename get_position<NextResult>::type | |
35 | > | |
36 | {}; | |
37 | public: | |
38 | typedef nth_of_c_impl type; | |
39 | ||
40 | template <class S, class Pos> | |
41 | struct apply : | |
42 | boost::mpl::eval_if< | |
43 | typename is_error< | |
44 | typename boost::mpl::front<Seq>::type::template apply<S, Pos> | |
45 | >::type, | |
46 | typename boost::mpl::front<Seq>::type::template apply<S, Pos>, | |
47 | apply_unchecked< | |
48 | typename boost::mpl::front<Seq>::type::template apply<S, Pos> | |
49 | > | |
50 | > | |
51 | {}; | |
52 | }; | |
53 | ||
54 | template <class Seq> | |
55 | struct nth_of_c_impl<0, Seq> | |
56 | { | |
57 | typedef nth_of_c_impl type; | |
58 | ||
59 | template <class S, class Pos> | |
60 | struct apply : | |
61 | boost::mpl::fold< | |
62 | typename boost::mpl::pop_front<Seq>::type, | |
63 | typename boost::mpl::front<Seq>::type::template apply< | |
64 | S, | |
65 | Pos | |
66 | >::type, | |
67 | skip_seq | |
68 | > | |
69 | {}; | |
70 | }; | |
71 | } | |
72 | } | |
73 | } | |
74 | } | |
75 | ||
76 | #endif | |
77 |