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1 | /*============================================================================= |
2 | Copyright (c) 2002-2003 Joel de Guzman | |
3 | Copyright (c) 2002-2003 Hartmut Kaiser | |
4 | http://spirit.sourceforge.net/ | |
5 | ||
6 | Use, modification and distribution is subject to the Boost Software | |
7 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
8 | http://www.boost.org/LICENSE_1_0.txt) | |
9 | =============================================================================*/ | |
10 | #if !defined(BOOST_SPIRIT_SUBRULE_IPP) | |
11 | #define BOOST_SPIRIT_SUBRULE_IPP | |
12 | ||
13 | #include <boost/mpl/if.hpp> | |
14 | ||
15 | namespace boost { namespace spirit { | |
16 | ||
17 | BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN | |
18 | ||
19 | template <typename FirstT, typename RestT> | |
20 | struct subrule_list; | |
21 | ||
22 | template <int ID, typename DefT, typename ContextT> | |
23 | struct subrule_parser; | |
24 | ||
25 | namespace impl { | |
26 | ||
27 | ||
28 | template <int N, typename ListT> | |
29 | struct get_subrule | |
30 | { | |
31 | // First case. ListT is non-empty but the list's | |
32 | // first item does not have the ID we are looking for. | |
33 | ||
34 | typedef typename get_subrule<N, typename ListT::rest_t>::type type; | |
35 | }; | |
36 | ||
37 | template <int ID, typename DefT, typename ContextT, typename RestT> | |
38 | struct get_subrule< | |
39 | ID, | |
40 | subrule_list< | |
41 | subrule_parser<ID, DefT, ContextT>, | |
42 | RestT> > | |
43 | { | |
44 | // Second case. ListT is non-empty and the list's | |
45 | // first item has the ID we are looking for. | |
46 | ||
47 | typedef DefT type; | |
48 | }; | |
49 | ||
50 | template <int ID> | |
51 | struct get_subrule<ID, nil_t> | |
52 | { | |
53 | // Third case. ListT is empty | |
54 | typedef nil_t type; | |
55 | }; | |
56 | ||
57 | ||
58 | template <typename T1, typename T2> | |
59 | struct get_result_t { | |
60 | ||
61 | // If the result type dictated by the context is nil_t (no closures | |
62 | // present), then the whole subrule_parser return type is equal to | |
63 | // the return type of the right hand side of this subrule_parser, | |
64 | // otherwise it is equal to the dictated return value. | |
65 | ||
66 | typedef typename mpl::if_< | |
67 | boost::is_same<T1, nil_t>, T2, T1 | |
68 | >::type type; | |
69 | }; | |
70 | ||
71 | template <int ID, typename ScannerT, typename ContextResultT> | |
72 | struct get_subrule_result | |
73 | { | |
74 | typedef typename | |
75 | impl::get_subrule<ID, typename ScannerT::list_t>::type | |
76 | parser_t; | |
77 | ||
78 | typedef typename parser_result<parser_t, ScannerT>::type | |
79 | def_result_t; | |
80 | ||
81 | typedef typename match_result<ScannerT, ContextResultT>::type | |
82 | context_result_t; | |
83 | ||
84 | typedef typename get_result_t<context_result_t, def_result_t>::type | |
85 | type; | |
86 | }; | |
87 | ||
88 | template <typename DefT, typename ScannerT, typename ContextResultT> | |
89 | struct get_subrule_parser_result | |
90 | { | |
91 | typedef typename parser_result<DefT, ScannerT>::type | |
92 | def_result_t; | |
93 | ||
94 | typedef typename match_result<ScannerT, ContextResultT>::type | |
95 | context_result_t; | |
96 | ||
97 | typedef typename get_result_t<context_result_t, def_result_t>::type | |
98 | type; | |
99 | }; | |
100 | ||
101 | template <typename SubruleT, int ID> | |
102 | struct same_subrule_id | |
103 | { | |
104 | BOOST_STATIC_CONSTANT(bool, value = (SubruleT::id == ID)); | |
105 | }; | |
106 | ||
107 | template <typename RT, typename ScannerT, int ID> | |
108 | struct parse_subrule | |
109 | { | |
110 | template <typename ListT> | |
111 | static void | |
112 | do_parse(RT& r, ScannerT const& scan, ListT const& list, mpl::true_) | |
113 | { | |
114 | r = list.first.rhs.parse(scan); | |
115 | } | |
116 | ||
117 | template <typename ListT> | |
118 | static void | |
119 | do_parse(RT& r, ScannerT const& scan, ListT const& list, mpl::false_) | |
120 | { | |
121 | typedef typename ListT::rest_t::first_t subrule_t; | |
122 | mpl::bool_<same_subrule_id<subrule_t, ID>::value> same_id; | |
123 | do_parse(r, scan, list.rest, same_id); | |
124 | } | |
125 | ||
126 | static void | |
127 | do_(RT& r, ScannerT const& scan) | |
128 | { | |
129 | typedef typename ScannerT::list_t::first_t subrule_t; | |
130 | mpl::bool_<same_subrule_id<subrule_t, ID>::value> same_id; | |
131 | do_parse(r, scan, scan.list, same_id); | |
132 | } | |
133 | }; | |
134 | ||
135 | } | |
136 | ||
137 | BOOST_SPIRIT_CLASSIC_NAMESPACE_END | |
138 | ||
139 | }} // namespace boost::spirit::impl | |
140 | ||
141 | #endif | |
142 |