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1 | /*============================================================================= |
2 | Copyright (c) 2001-2011 Joel de Guzman | |
3 | Copyright (c) 2001-2011 Hartmut Kaiser | |
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(SPIRIT_OPTIONAL_MARCH_23_2007_1117PM) | |
9 | #define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM | |
10 | ||
11 | #if defined(_MSC_VER) | |
12 | #pragma once | |
13 | #endif | |
14 | ||
15 | #include <boost/spirit/home/support/unused.hpp> | |
16 | #include <boost/spirit/home/qi/detail/attributes.hpp> | |
17 | #include <boost/spirit/home/support/has_semantic_action.hpp> | |
18 | #include <boost/spirit/home/support/handles_container.hpp> | |
19 | #include <boost/spirit/home/support/info.hpp> | |
20 | #include <boost/spirit/home/support/container.hpp> | |
21 | #include <boost/spirit/home/qi/parser.hpp> | |
22 | #include <boost/spirit/home/qi/meta_compiler.hpp> | |
23 | #include <boost/spirit/home/qi/detail/assign_to.hpp> | |
24 | #include <boost/optional.hpp> | |
25 | #include <vector> | |
26 | ||
27 | namespace boost { namespace spirit | |
28 | { | |
29 | /////////////////////////////////////////////////////////////////////////// | |
30 | // Enablers | |
31 | /////////////////////////////////////////////////////////////////////////// | |
32 | template <> | |
33 | struct use_operator<qi::domain, proto::tag::negate> // enables -p | |
34 | : mpl::true_ {}; | |
35 | }} | |
36 | ||
37 | namespace boost { namespace spirit { namespace qi | |
38 | { | |
39 | template <typename Subject> | |
40 | struct optional : unary_parser<optional<Subject> > | |
41 | { | |
42 | typedef Subject subject_type; | |
43 | ||
44 | template <typename Context, typename Iterator> | |
45 | struct attribute | |
46 | { | |
47 | // Build a boost::optional from the subject's attribute. Note | |
48 | // that boost::optional may return unused_type if the | |
49 | // subject's attribute is an unused_type. | |
50 | typedef typename | |
51 | traits::build_optional< | |
52 | typename traits:: | |
53 | attribute_of<Subject, Context, Iterator>::type | |
54 | >::type | |
55 | type; | |
56 | }; | |
57 | ||
58 | optional(Subject const& subject_) | |
59 | : subject(subject_) {} | |
60 | ||
61 | template <typename Iterator, typename Context | |
62 | , typename Skipper, typename Attribute> | |
63 | bool parse_impl(Iterator& first, Iterator const& last | |
64 | , Context& context, Skipper const& skipper | |
65 | , Attribute& attr_, mpl::false_) const | |
66 | { | |
67 | // create a local value if Attribute is not unused_type | |
68 | typename spirit::result_of::optional_value<Attribute>::type val = | |
69 | typename spirit::result_of::optional_value<Attribute>::type(); | |
70 | ||
71 | if (subject.parse(first, last, context, skipper, val)) | |
72 | { | |
73 | // assign the parsed value into our attribute | |
74 | spirit::traits::assign_to(val, attr_); | |
75 | } | |
76 | return true; | |
77 | } | |
78 | ||
79 | template <typename Iterator, typename Context | |
80 | , typename Skipper, typename Attribute> | |
81 | bool parse_impl(Iterator& first, Iterator const& last | |
82 | , Context& context, Skipper const& skipper | |
83 | , Attribute& attr_, mpl::true_) const | |
84 | { | |
85 | subject.parse(first, last, context, skipper, attr_); | |
86 | return true; | |
87 | } | |
88 | ||
89 | template <typename Iterator, typename Context | |
90 | , typename Skipper, typename Attribute> | |
91 | bool parse(Iterator& first, Iterator const& last | |
92 | , Context& context, Skipper const& skipper | |
93 | , Attribute& attr_) const | |
94 | { | |
95 | typedef typename spirit::result_of::optional_value<Attribute>::type | |
96 | attribute_type; | |
97 | ||
98 | return parse_impl(first, last, context, skipper, attr_ | |
99 | , traits::is_container<attribute_type>()); | |
100 | } | |
101 | ||
102 | template <typename Context> | |
103 | info what(Context& context) const | |
104 | { | |
105 | return info("optional", subject.what(context)); | |
106 | } | |
107 | ||
108 | Subject subject; | |
109 | }; | |
110 | ||
111 | /////////////////////////////////////////////////////////////////////////// | |
112 | // Parser generators: make_xxx function (objects) | |
113 | /////////////////////////////////////////////////////////////////////////// | |
114 | template <typename Elements, typename Modifiers> | |
115 | struct make_composite<proto::tag::negate, Elements, Modifiers> | |
116 | : make_unary_composite<Elements, optional> | |
117 | {}; | |
118 | }}} | |
119 | ||
120 | namespace boost { namespace spirit { namespace traits | |
121 | { | |
122 | /////////////////////////////////////////////////////////////////////////// | |
123 | template <typename Subject> | |
124 | struct has_semantic_action<qi::optional<Subject> > | |
125 | : unary_has_semantic_action<Subject> {}; | |
126 | ||
127 | /////////////////////////////////////////////////////////////////////////// | |
128 | template <typename Subject, typename Attribute, typename Context | |
129 | , typename Iterator> | |
130 | struct handles_container<qi::optional<Subject>, Attribute | |
131 | , Context, Iterator> | |
132 | : mpl::true_ {}; | |
133 | }}} | |
134 | ||
135 | #endif |