qi/directive/hold.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
0003
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 =============================================================================*/
0007 #ifndef BOOST_SPIRIT_QI_DIRECTIVE_HOLD_HPP
0008 #define BOOST_SPIRIT_QI_DIRECTIVE_HOLD_HPP
0009
0010 #if defined(_MSC_VER)
0011 #pragma once
0012 #endif
0013
0014 #include <boost/spirit/home/qi/meta_compiler.hpp>
0015 #include <boost/spirit/home/qi/skip_over.hpp>
0016 #include <boost/spirit/home/qi/parser.hpp>
0017 #include <boost/spirit/home/support/attributes.hpp>
0018 #include <boost/spirit/home/support/info.hpp>
0019 #include <boost/spirit/home/support/common_terminals.hpp>
0020 #include <boost/spirit/home/support/unused.hpp>
0021 #include <boost/spirit/home/support/has_semantic_action.hpp>
0022 #include <boost/spirit/home/support/handles_container.hpp>
0023
0024 namespace boost { namespace spirit
0025 {
0026     ///////////////////////////////////////////////////////////////////////////
0027     // Enablers
0028     ///////////////////////////////////////////////////////////////////////////
0029     template <>
0030     struct use_directive<qi::domain, tag::hold> // enables hold
0031       : mpl::true_ {};
0032 }}
0033
0034 namespace boost { namespace spirit { namespace qi
0035 {
0036 #ifndef BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
0037     using spirit::hold;
0038 #endif
0039     using spirit::hold_type;
0040
0041     template <typename Subject>
0042     struct hold_directive : unary_parser<hold_directive<Subject> >
0043     {
0044         typedef Subject subject_type;
0045         hold_directive(Subject const& subject_)
0046           : subject(subject_) {}
0047
0048         template <typename Context, typename Iterator>
0049         struct attribute
0050         {
0051             typedef typename
0052                 traits::attribute_of<subject_type, Context, Iterator>::type
0053             type;
0054         };
0055
0056         template <typename Iterator, typename Context
0057           , typename Skipper, typename Attribute>
0058         bool parse(Iterator& first, Iterator const& last
0059           , Context& context, Skipper const& skipper, Attribute& attr_) const
0060         {
0061             Attribute copy(attr_);
0062             if (subject.parse(first, last, context, skipper, copy))
0063             {
0064                 traits::swap_impl(copy, attr_);
0065                 return true;
0066             }
0067             return false;
0068         }
0069
0070         template <typename Context>
0071         info what(Context& context) const
0072         {
0073             return info("hold", subject.what(context));
0074
0075         }
0076
0077         Subject subject;
0078     };
0079
0080     ///////////////////////////////////////////////////////////////////////////
0081     // Parser generators: make_xxx function (objects)
0082     ///////////////////////////////////////////////////////////////////////////
0083     template <typename Subject, typename Modifiers>
0084     struct make_directive<tag::hold, Subject, Modifiers>
0085     {
0086         typedef hold_directive<Subject> result_type;
0087         result_type operator()(unused_type, Subject const& subject, unused_type) const
0088         {
0089             return result_type(subject);
0090         }
0091     };
0092 }}}
0093
0094 namespace boost { namespace spirit { namespace traits
0095 {
0096     ///////////////////////////////////////////////////////////////////////////
0097     template <typename Subject>
0098     struct has_semantic_action<qi::hold_directive<Subject> >
0099       : unary_has_semantic_action<Subject> {};
0100
0101     ///////////////////////////////////////////////////////////////////////////
0102     template <typename Subject, typename Attribute, typename Context
0103         , typename Iterator>
0104     struct handles_container<qi::hold_directive<Subject>, Attribute
0105         , Context, Iterator>
0106       : unary_handles_container<Subject, Attribute, Context, Iterator> {};
0107 }}}
0108
0109 #endif