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1 | /*============================================================================= |
2 | Copyright (c) 2001-2014 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 | =============================================================================*/ | |
11fdf7f2 TL |
8 | #if !defined(BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM) |
9 | #define BOOST_SPIRIT_X3_OPTIONAL_MARCH_23_2007_1117PM | |
7c673cae FG |
10 | |
11 | #include <boost/spirit/home/x3/core/proxy.hpp> | |
12 | #include <boost/spirit/home/x3/core/detail/parse_into_container.hpp> | |
13 | #include <boost/spirit/home/x3/support/traits/attribute_of.hpp> | |
14 | #include <boost/spirit/home/x3/support/traits/move_to.hpp> | |
15 | #include <boost/spirit/home/x3/support/traits/optional_traits.hpp> | |
16 | #include <boost/spirit/home/x3/support/traits/attribute_category.hpp> | |
17 | ||
18 | namespace boost { namespace spirit { namespace x3 | |
19 | { | |
20 | template <typename Subject> | |
21 | struct optional : proxy<Subject, optional<Subject>> | |
22 | { | |
23 | typedef proxy<Subject, optional<Subject>> base_type; | |
1e59de90 | 24 | static bool const is_pass_through_unary = false; |
7c673cae FG |
25 | static bool const handles_container = true; |
26 | ||
f67539c2 | 27 | constexpr optional(Subject const& subject) |
7c673cae FG |
28 | : base_type(subject) {} |
29 | ||
30 | using base_type::parse_subject; | |
31 | ||
32 | // Attribute is a container | |
33 | template <typename Iterator, typename Context | |
34 | , typename RContext, typename Attribute> | |
35 | bool parse_subject(Iterator& first, Iterator const& last | |
36 | , Context const& context, RContext& rcontext, Attribute& attr | |
37 | , traits::container_attribute) const | |
38 | { | |
39 | detail::parse_into_container( | |
40 | this->subject, first, last, context, rcontext, attr); | |
41 | return true; | |
42 | } | |
43 | ||
44 | // Attribute is an optional | |
45 | template <typename Iterator, typename Context | |
46 | , typename RContext, typename Attribute> | |
47 | bool parse_subject(Iterator& first, Iterator const& last | |
48 | , Context const& context, RContext& rcontext, Attribute& attr | |
49 | , traits::optional_attribute) const | |
50 | { | |
51 | typedef typename | |
52 | x3::traits::optional_value<Attribute>::type | |
53 | value_type; | |
54 | ||
55 | // create a local value | |
92f5a8d4 | 56 | value_type val{}; |
7c673cae FG |
57 | |
58 | if (this->subject.parse(first, last, context, rcontext, val)) | |
59 | { | |
60 | // assign the parsed value into our attribute | |
61 | x3::traits::move_to(val, attr); | |
62 | } | |
63 | return true; | |
64 | } | |
65 | }; | |
66 | ||
67 | template <typename Subject> | |
f67539c2 | 68 | constexpr optional<typename extension::as_parser<Subject>::value_type> |
7c673cae FG |
69 | operator-(Subject const& subject) |
70 | { | |
71 | return { as_parser(subject) }; | |
72 | } | |
73 | }}} | |
74 | ||
75 | namespace boost { namespace spirit { namespace x3 { namespace traits | |
76 | { | |
77 | template <typename Subject, typename Context> | |
78 | struct attribute_of<x3::optional<Subject>, Context> | |
79 | : build_optional< | |
80 | typename attribute_of<Subject, Context>::type> {}; | |
81 | }}}} | |
82 | ||
83 | #endif |