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1 | /*============================================================================= |
2 | Copyright (c) 2001-2011 Joel de Guzman | |
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 | =============================================================================*/ | |
7 | #if !defined(SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM) | |
8 | #define SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM | |
9 | ||
10 | #if defined(_MSC_VER) | |
11 | #pragma once | |
12 | #endif | |
13 | ||
14 | #include <boost/spirit/home/qi/domain.hpp> | |
15 | #include <boost/spirit/home/qi/meta_compiler.hpp> | |
16 | #include <boost/spirit/home/qi/parser.hpp> | |
17 | #include <boost/spirit/home/qi/detail/attributes.hpp> | |
18 | #include <boost/spirit/home/support/info.hpp> | |
19 | #include <boost/spirit/home/support/has_semantic_action.hpp> | |
20 | #include <boost/spirit/home/support/handles_container.hpp> | |
21 | #include <boost/fusion/include/at.hpp> | |
22 | ||
23 | namespace boost { namespace spirit | |
24 | { | |
25 | /////////////////////////////////////////////////////////////////////////// | |
26 | // Enablers | |
27 | /////////////////////////////////////////////////////////////////////////// | |
28 | template <> | |
29 | struct use_operator<qi::domain, proto::tag::minus> // enables - | |
30 | : mpl::true_ {}; | |
31 | }} | |
32 | ||
33 | namespace boost { namespace spirit { namespace qi | |
34 | { | |
35 | template <typename Left, typename Right> | |
36 | struct difference : binary_parser<difference<Left, Right> > | |
37 | { | |
38 | typedef Left left_type; | |
39 | typedef Right right_type; | |
40 | ||
41 | template <typename Context, typename Iterator> | |
42 | struct attribute | |
43 | { | |
44 | typedef typename | |
45 | traits::attribute_of<left_type, Context, Iterator>::type | |
46 | type; | |
47 | }; | |
48 | ||
49 | difference(Left const& left_, Right const& right_) | |
50 | : left(left_), right(right_) {} | |
51 | ||
52 | template <typename Iterator, typename Context | |
53 | , typename Skipper, typename Attribute> | |
54 | bool parse(Iterator& first, Iterator const& last | |
55 | , Context& context, Skipper const& skipper | |
56 | , Attribute& attr_) const | |
57 | { | |
58 | // Unlike classic Spirit, with this version of difference, the rule | |
59 | // lit("policeman") - "police" will always fail to match. | |
60 | ||
61 | // Spirit2 does not count the matching chars while parsing and | |
62 | // there is no reliable and fast way to check if the LHS matches | |
63 | // more than the RHS. | |
64 | ||
65 | // Try RHS first | |
66 | Iterator start = first; | |
67 | if (right.parse(first, last, context, skipper, unused)) | |
68 | { | |
69 | // RHS succeeds, we fail. | |
70 | first = start; | |
71 | return false; | |
72 | } | |
73 | // RHS fails, now try LHS | |
74 | return left.parse(first, last, context, skipper, attr_); | |
75 | } | |
76 | ||
77 | template <typename Context> | |
78 | info what(Context& context) const | |
79 | { | |
80 | return info("difference", | |
81 | std::make_pair(left.what(context), right.what(context))); | |
82 | } | |
83 | ||
84 | Left left; | |
85 | Right right; | |
86 | }; | |
87 | ||
88 | /////////////////////////////////////////////////////////////////////////// | |
89 | // Parser generators: make_xxx function (objects) | |
90 | /////////////////////////////////////////////////////////////////////////// | |
91 | template <typename Elements, typename Modifiers> | |
92 | struct make_composite<proto::tag::minus, Elements, Modifiers> | |
93 | : make_binary_composite<Elements, difference> | |
94 | {}; | |
95 | }}} | |
96 | ||
97 | namespace boost { namespace spirit { namespace traits | |
98 | { | |
99 | /////////////////////////////////////////////////////////////////////////// | |
100 | template <typename Left, typename Right> | |
101 | struct has_semantic_action<qi::difference<Left, Right> > | |
102 | : binary_has_semantic_action<Left, Right> {}; | |
103 | ||
104 | /////////////////////////////////////////////////////////////////////////// | |
105 | template <typename Left, typename Right, typename Attribute | |
106 | , typename Context, typename Iterator> | |
107 | struct handles_container<qi::difference<Left, Right>, Attribute, Context | |
108 | , Iterator> | |
109 | : binary_handles_container<Left, Right, Attribute, Context, Iterator> {}; | |
110 | }}} | |
111 | ||
112 | #endif |