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 #ifndef BOOST_SPIRIT_QI_DIRECTIVE_HOLD_HPP
8 #define BOOST_SPIRIT_QI_DIRECTIVE_HOLD_HPP
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/skip_over.hpp>
16 #include <boost/spirit/home/qi/parser.hpp>
17 #include <boost/spirit/home/support/attributes.hpp>
18 #include <boost/spirit/home/support/info.hpp>
19 #include <boost/spirit/home/support/common_terminals.hpp>
20 #include <boost/spirit/home/support/unused.hpp>
21 #include <boost/spirit/home/support/has_semantic_action.hpp>
22 #include <boost/spirit/home/support/handles_container.hpp>
23 
24 namespace boost { namespace spirit
25 {
26     ///////////////////////////////////////////////////////////////////////////
27     // Enablers
28     ///////////////////////////////////////////////////////////////////////////
29     template <>
30     struct use_directive<qi::domain, tag::hold> // enables hold
31       : mpl::true_ {};
32 }}
33 
34 namespace boost { namespace spirit { namespace qi
35 {
36 #ifndef BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
37     using spirit::hold;
38 #endif
39     using spirit::hold_type;
40 
41     template <typename Subject>
42     struct hold_directive : unary_parser<hold_directive<Subject> >
43     {
44         typedef Subject subject_type;
hold_directiveboost::spirit::qi::hold_directive45         hold_directive(Subject const& subject_)
46           : subject(subject_) {}
47 
48         template <typename Context, typename Iterator>
49         struct attribute
50         {
51             typedef typename
52                 traits::attribute_of<subject_type, Context, Iterator>::type
53             type;
54         };
55 
56         template <typename Iterator, typename Context
57           , typename Skipper, typename Attribute>
parseboost::spirit::qi::hold_directive58         bool parse(Iterator& first, Iterator const& last
59           , Context& context, Skipper const& skipper, Attribute& attr_) const
60         {
61             Attribute copy(attr_);
62             if (subject.parse(first, last, context, skipper, copy))
63             {
64                 traits::swap_impl(copy, attr_);
65                 return true;
66             }
67             return false;
68         }
69 
70         template <typename Context>
whatboost::spirit::qi::hold_directive71         info what(Context& context) const
72         {
73             return info("hold", subject.what(context));
74 
75         }
76 
77         Subject subject;
78     };
79 
80     ///////////////////////////////////////////////////////////////////////////
81     // Parser generators: make_xxx function (objects)
82     ///////////////////////////////////////////////////////////////////////////
83     template <typename Subject, typename Modifiers>
84     struct make_directive<tag::hold, Subject, Modifiers>
85     {
86         typedef hold_directive<Subject> result_type;
operator ()boost::spirit::qi::make_directive87         result_type operator()(unused_type, Subject const& subject, unused_type) const
88         {
89             return result_type(subject);
90         }
91     };
92 }}}
93 
94 namespace boost { namespace spirit { namespace traits
95 {
96     ///////////////////////////////////////////////////////////////////////////
97     template <typename Subject>
98     struct has_semantic_action<qi::hold_directive<Subject> >
99       : unary_has_semantic_action<Subject> {};
100 
101     ///////////////////////////////////////////////////////////////////////////
102     template <typename Subject, typename Attribute, typename Context
103         , typename Iterator>
104     struct handles_container<qi::hold_directive<Subject>, Attribute
105         , Context, Iterator>
106       : unary_handles_container<Subject, Attribute, Context, Iterator> {};
107 }}}
108 
109 #endif
110