x3/directive/omit.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2014 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 #if !defined(BOOST_SPIRIT_X3_OMIT_MARCH_24_2007_0802AM)
0008 #define BOOST_SPIRIT_X3_OMIT_MARCH_24_2007_0802AM
0009
0010 #include <boost/spirit/home/x3/support/unused.hpp>
0011 #include <boost/spirit/home/x3/core/parser.hpp>
0012
0013 namespace boost { namespace spirit { namespace x3
0014 {
0015     ///////////////////////////////////////////////////////////////////////////
0016     // omit_directive forces the attribute of subject parser
0017     // to be unused_type
0018     ///////////////////////////////////////////////////////////////////////////
0019     template <typename Subject>
0020     struct omit_directive : unary_parser<Subject, omit_directive<Subject>>
0021     {
0022         typedef unary_parser<Subject, omit_directive<Subject> > base_type;
0023         typedef unused_type attribute_type;
0024         static bool const has_attribute = false;
0025
0026         typedef Subject subject_type;
0027         constexpr omit_directive(Subject const& subject)
0028           : base_type(subject) {}
0029
0030         template <typename Iterator, typename Context, typename RContext>
0031         bool parse(Iterator& first, Iterator const& last
0032           , Context const& context, RContext& rcontext, unused_type) const
0033         {
0034             return this->subject.parse(first, last, context, rcontext, unused);
0035         }
0036     };
0037
0038     struct omit_gen
0039     {
0040         template <typename Subject>
0041         constexpr omit_directive<typename extension::as_parser<Subject>::value_type>
0042         operator[](Subject const& subject) const
0043         {
0044             return { as_parser(subject) };
0045         }
0046     };
0047
0048     constexpr auto omit = omit_gen{};
0049 }}}
0050
0051 #endif