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1 | // Copyright (c) 2001-2011 Joel de Guzman |
2 | // Copyright (c) 2001-2011 Hartmut Kaiser | |
3 | // | |
4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
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7 | #ifndef BOOST_SPIRIT_KARMA_OPERATOR_OPTIONAL_HPP |
8 | #define BOOST_SPIRIT_KARMA_OPERATOR_OPTIONAL_HPP | |
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9 | |
10 | #if defined(_MSC_VER) | |
11 | #pragma once | |
12 | #endif | |
13 | ||
14 | #include <boost/spirit/home/karma/domain.hpp> | |
15 | #include <boost/spirit/home/karma/generator.hpp> | |
16 | #include <boost/spirit/home/karma/meta_compiler.hpp> | |
17 | #include <boost/spirit/home/support/info.hpp> | |
18 | #include <boost/spirit/home/support/unused.hpp> | |
19 | #include <boost/spirit/home/karma/detail/attributes.hpp> | |
20 | #include <boost/spirit/home/support/container.hpp> | |
21 | #include <boost/spirit/home/support/has_semantic_action.hpp> | |
22 | #include <boost/spirit/home/support/handles_container.hpp> | |
23 | #include <boost/mpl/assert.hpp> | |
24 | #include <boost/optional.hpp> | |
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25 | #include <boost/proto/operators.hpp> |
26 | #include <boost/proto/tags.hpp> | |
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27 | #include <boost/type_traits/is_convertible.hpp> |
28 | ||
29 | namespace boost { namespace spirit | |
30 | { | |
31 | /////////////////////////////////////////////////////////////////////////// | |
32 | // Enablers | |
33 | /////////////////////////////////////////////////////////////////////////// | |
34 | template <> | |
35 | struct use_operator<karma::domain, proto::tag::negate> // enables -g | |
36 | : mpl::true_ {}; | |
37 | ||
38 | }} | |
39 | ||
40 | /////////////////////////////////////////////////////////////////////////////// | |
41 | namespace boost { namespace spirit { namespace karma | |
42 | { | |
43 | /////////////////////////////////////////////////////////////////////////// | |
44 | template <typename Subject> | |
45 | struct optional : unary_generator<optional<Subject> > | |
46 | { | |
47 | typedef Subject subject_type; | |
48 | typedef typename subject_type::properties properties; | |
49 | ||
50 | // Build a boost::optional from the subject's attribute. Note | |
51 | // that boost::optional may return unused_type if the | |
52 | // subject's attribute is an unused_type. | |
53 | template <typename Context, typename Iterator = unused_type> | |
54 | struct attribute | |
55 | : traits::build_optional< | |
56 | typename traits::attribute_of<Subject, Context, Iterator>::type | |
57 | > | |
58 | {}; | |
59 | ||
60 | optional(Subject const& subject) | |
61 | : subject(subject) {} | |
62 | ||
63 | template < | |
64 | typename OutputIterator, typename Context, typename Delimiter | |
65 | , typename Attribute> | |
66 | bool generate(OutputIterator& sink, Context& ctx | |
67 | , Delimiter const& d, Attribute const& attr) const | |
68 | { | |
69 | if (traits::has_optional_value(attr)) | |
70 | subject.generate(sink, ctx, d, traits::optional_value(attr)); | |
71 | return sink_is_good(sink); | |
72 | } | |
73 | ||
74 | template <typename Context> | |
75 | info what(Context& context) const | |
76 | { | |
77 | return info("optional", subject.what(context)); | |
78 | } | |
79 | ||
80 | Subject subject; | |
81 | }; | |
82 | ||
83 | /////////////////////////////////////////////////////////////////////////// | |
84 | // Generator generators: make_xxx function (objects) | |
85 | /////////////////////////////////////////////////////////////////////////// | |
86 | template <typename Elements, typename Modifiers> | |
87 | struct make_composite<proto::tag::negate, Elements, Modifiers> | |
88 | : make_unary_composite<Elements, optional> {}; | |
89 | ||
90 | }}} | |
91 | ||
92 | namespace boost { namespace spirit { namespace traits | |
93 | { | |
94 | /////////////////////////////////////////////////////////////////////////// | |
95 | template <typename Subject> | |
96 | struct has_semantic_action<karma::optional<Subject> > | |
97 | : unary_has_semantic_action<Subject> {}; | |
98 | ||
99 | /////////////////////////////////////////////////////////////////////////// | |
100 | template <typename Subject, typename Attribute, typename Context | |
101 | , typename Iterator> | |
102 | struct handles_container<karma::optional<Subject>, Attribute, Context | |
103 | , Iterator> | |
104 | : mpl::true_ {}; | |
105 | }}} | |
106 | ||
107 | #endif |