x3/core/skip_over.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_SKIP_APRIL_16_2006_0625PM)
0008 #define BOOST_SPIRIT_X3_SKIP_APRIL_16_2006_0625PM
0009
0010 #include <boost/spirit/home/x3/support/unused.hpp>
0011 #include <boost/spirit/home/x3/support/context.hpp>
0012 #include <boost/spirit/home/x3/support/traits/attribute_category.hpp>
0013 #include <boost/mpl/bool.hpp>
0014 #include <boost/mpl/not.hpp>
0015 #include <boost/type_traits/remove_cv.hpp>
0016 #include <boost/type_traits/remove_reference.hpp>
0017 #include <boost/utility/declval.hpp>
0018
0019 namespace boost { namespace spirit { namespace x3
0020 {
0021     ///////////////////////////////////////////////////////////////////////////
0022     // Move the /first/ iterator to the first non-matching position
0023     // given a skip-parser. The function is a no-op if unused_type or
0024     // unused_skipper is passed as the skip-parser.
0025     ///////////////////////////////////////////////////////////////////////////
0026     template <typename Skipper>
0027     struct unused_skipper : unused_type
0028     {
0029         unused_skipper(Skipper const& skipper)
0030           : skipper(skipper) {}
0031         Skipper const& skipper;
0032     };
0033
0034     namespace detail
0035     {
0036         template <typename Skipper>
0037         struct is_unused_skipper
0038           : mpl::false_ {};
0039
0040         template <typename Skipper>
0041         struct is_unused_skipper<unused_skipper<Skipper>>
0042           : mpl::true_ {};
0043
0044         template <>
0045         struct is_unused_skipper<unused_type>
0046           : mpl::true_ {};
0047
0048         template <typename Skipper>
0049         inline Skipper const&
0050         get_unused_skipper(Skipper const& skipper)
0051         {
0052             return skipper;
0053         }
0054         template <typename Skipper>
0055         inline Skipper const&
0056         get_unused_skipper(unused_skipper<Skipper> const& unused_skipper)
0057         {
0058             return unused_skipper.skipper;
0059         }
0060
0061         template <typename Iterator, typename Skipper>
0062         inline void skip_over(
0063             Iterator& first, Iterator const& last, Skipper const& skipper)
0064         {
0065             while (skipper.parse(first, last, unused, unused, unused))
0066                 /***/;
0067         }
0068
0069         template <typename Iterator>
0070         inline void skip_over(Iterator&, Iterator const&, unused_type)
0071         {
0072         }
0073
0074         template <typename Iterator, typename Skipper>
0075         inline void skip_over(
0076             Iterator&, Iterator const&, unused_skipper<Skipper> const&)
0077         {
0078         }
0079     }
0080
0081     // this tag is used to find the skipper from the context
0082     struct skipper_tag;
0083
0084     template <typename Context>
0085     struct has_skipper
0086       : mpl::not_<detail::is_unused_skipper<
0087             typename remove_cv<typename remove_reference<
0088                 decltype(x3::get<skipper_tag>(boost::declval<Context>()))
0089             >::type>::type
0090         >> {};
0091
0092     template <typename Iterator, typename Context>
0093     inline void skip_over(
0094         Iterator& first, Iterator const& last, Context const& context)
0095     {
0096         detail::skip_over(first, last, x3::get<skipper_tag>(context));
0097     }
0098 }}}
0099
0100 #endif