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_ACTION_JANUARY_07_2007_1128AM)
8 #define SPIRIT_ACTION_JANUARY_07_2007_1128AM
9 
10 #if defined(_MSC_VER)
11 #pragma once
12 #endif
13 
14 #include <boost/spirit/home/qi/meta_compiler.hpp>
15 #include <boost/spirit/home/qi/parser.hpp>
16 #include <boost/spirit/home/qi/detail/attributes.hpp>
17 #include <boost/spirit/home/support/argument.hpp>
18 #include <boost/spirit/home/support/context.hpp>
19 #include <boost/spirit/home/support/unused.hpp>
20 #include <boost/spirit/home/support/info.hpp>
21 #include <boost/spirit/home/support/action_dispatch.hpp>
22 #include <boost/spirit/home/support/handles_container.hpp>
23 
24 #include <boost/mpl/bool.hpp>
25 #include <boost/mpl/if.hpp>
26 #include <boost/type_traits/remove_const.hpp>
27 #include <boost/type_traits/is_same.hpp>
28 
29 namespace boost { namespace spirit { namespace qi
30 {
31     BOOST_PP_REPEAT(SPIRIT_ARGUMENTS_LIMIT, SPIRIT_USING_ARGUMENT, _)
32 
33     template <typename Subject, typename Action>
34     struct action : unary_parser<action<Subject, Action> >
35     {
36         typedef Subject subject_type;
37         typedef Action action_type;
38 
39         template <typename Context, typename Iterator>
40         struct attribute
41           : traits::attribute_of<Subject, Context, Iterator>
42         {};
43 
actionboost::spirit::qi::action44         action(Subject const& subject_, Action f_)
45           : subject(subject_), f(f_) {}
46 
47 #ifndef BOOST_SPIRIT_ACTIONS_ALLOW_ATTR_COMPAT
48         template <typename Iterator, typename Context
49           , typename Skipper, typename Attribute>
parseboost::spirit::qi::action50         bool parse(Iterator& first, Iterator const& last
51           , Context& context, Skipper const& skipper
52           , Attribute& attr_) const
53         {
54             typedef typename attribute<Context, Iterator>::type attr_type;
55             typedef traits::make_attribute<attr_type, Attribute> make_attribute;
56 
57             // create an attribute if one is not supplied
58             typedef traits::transform_attribute<
59                 typename make_attribute::type, attr_type, domain> transform;
60 
61             typename make_attribute::type made_attr = make_attribute::call(attr_);
62             typename transform::type attr = transform::pre(made_attr);
63 
64             Iterator save = first;
65             if (subject.parse(first, last, context, skipper, attr))
66             {
67                 // call the function, passing the attribute, the context.
68                 // The client can return false to fail parsing.
69                 if (traits::action_dispatch<Subject>()(f, attr, context))
70                 {
71                     // Do up-stream transformation, this integrates the results
72                     // back into the original attribute value, if appropriate.
73                     traits::post_transform(attr_, attr);
74                     return true;
75                 }
76 
77                 // reset iterators if semantic action failed the match
78                 // retrospectively
79                 first = save;
80             }
81             return false;
82         }
83 #else
84         template <typename Iterator, typename Context
85           , typename Skipper, typename Attribute>
parseboost::spirit::qi::action86         bool parse(Iterator& first, Iterator const& last
87           , Context& context, Skipper const& skipper
88           , Attribute& attr) const
89         {
90             Iterator save = first;
91             if (subject.parse(first, last, context, skipper, attr)) // Use the attribute as-is
92             {
93                 // call the function, passing the attribute, the context.
94                 // The client can return false to fail parsing.
95                 if (traits::action_dispatch<Subject>()(f, attr, context))
96                     return true;
97 
98                 // reset iterators if semantic action failed the match
99                 // retrospectively
100                 first = save;
101             }
102             return false;
103         }
104 
105         template <typename Iterator, typename Context
106           , typename Skipper>
parseboost::spirit::qi::action107         bool parse(Iterator& first, Iterator const& last
108           , Context& context, Skipper const& skipper
109           , unused_type) const
110         {
111             typedef typename attribute<Context, Iterator>::type attr_type;
112             typedef traits::make_attribute<attr_type, unused_type> make_attribute;
113 
114             // synthesize the attribute since one is not supplied
115             typedef traits::transform_attribute<
116                 typename make_attribute::type, attr_type, domain> transform;
117 
118             typename make_attribute::type made_attr = make_attribute::call(unused_type());
119             typename transform::type attr = transform::pre(made_attr);
120 
121             Iterator save = first;
122             if (subject.parse(first, last, context, skipper, attr))
123             {
124                 // call the function, passing the attribute, the context.
125                 // The client can return false to fail parsing.
126                 if (traits::action_dispatch<Subject>()(f, attr, context))
127                     return true;
128 
129                 // reset iterators if semantic action failed the match
130                 // retrospectively
131                 first = save;
132             }
133             return false;
134         }
135 #endif
136 
137         template <typename Context>
whatboost::spirit::qi::action138         info what(Context& context) const
139         {
140             // the action is transparent (does not add any info)
141             return subject.what(context);
142         }
143 
144         Subject subject;
145         Action f;
146 
147     private:
148         // silence MSVC warning C4512: assignment operator could not be generated
149         action& operator= (action const&);
150     };
151 }}}
152 
153 namespace boost { namespace spirit
154 {
155     // Qi action meta-compiler
156     template <>
157     struct make_component<qi::domain, tag::action>
158     {
159         template <typename Sig>
160         struct result;
161 
162         template <typename This, typename Elements, typename Modifiers>
163         struct result<This(Elements, Modifiers)>
164         {
165             typedef typename
166                 remove_const<typename Elements::car_type>::type
167             subject_type;
168 
169             typedef typename
170                 remove_const<typename Elements::cdr_type::car_type>::type
171             action_type;
172 
173             typedef qi::action<subject_type, action_type> type;
174         };
175 
176         template <typename Elements>
177         typename result<make_component(Elements, unused_type)>::type
operator ()boost::spirit::make_component178         operator()(Elements const& elements, unused_type) const
179         {
180             typename result<make_component(Elements, unused_type)>::type
181                 result(elements.car, elements.cdr.car);
182             return result;
183         }
184     };
185 }}
186 
187 namespace boost { namespace spirit { namespace traits
188 {
189     ///////////////////////////////////////////////////////////////////////////
190     template <typename Subject, typename Action>
191     struct has_semantic_action<qi::action<Subject, Action> >
192       : mpl::true_ {};
193 
194     ///////////////////////////////////////////////////////////////////////////
195     template <typename Subject, typename Action, typename Attribute
196         , typename Context, typename Iterator>
197     struct handles_container<qi::action<Subject, Action>, Attribute
198         , Context, Iterator>
199       : unary_handles_container<Subject, Attribute, Context, Iterator> {};
200 }}}
201 
202 #endif
203