boost/spirit/home/x3/directive/lexeme.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 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(BOOST_SPIRIT_X3_LEXEME_MARCH_24_2007_0802AM)
   8 #define BOOST_SPIRIT_X3_LEXEME_MARCH_24_2007_0802AM
   9
  10 #include <boost/spirit/home/x3/support/context.hpp>
  11 #include <boost/spirit/home/x3/support/unused.hpp>
  12 #include <boost/spirit/home/x3/core/skip_over.hpp>
  13 #include <boost/spirit/home/x3/core/parser.hpp>
  14 #include <boost/type_traits/remove_reference.hpp>
  15 #include <boost/utility/enable_if.hpp>
  16
  17 namespace boost { namespace spirit { namespace x3
  18 {
  19     template <typename Subject>
  20     struct lexeme_directive : unary_parser<Subject, lexeme_directive<Subject>>
  21     {
  22         typedef unary_parser<Subject, lexeme_directive<Subject> > base_type;
  23         static bool const is_pass_through_unary = true;
  24         static bool const handles_container = Subject::handles_container;
  25
  26         lexeme_directive(Subject const& subject)
  27           : base_type(subject) {}
  28
  29         template <typename Iterator, typename Context
  30           , typename RContext, typename Attribute>
  31         typename enable_if<has_skipper<Context>, bool>::type
  32         parse(Iterator& first, Iterator const& last
  33           , Context const& context, RContext& rcontext, Attribute& attr) const
  34         {
  35             x3::skip_over(first, last, context);
  36             auto const& skipper = x3::get<skipper_tag>(context);
  37
  38             typedef unused_skipper<
  39                 typename remove_reference<decltype(skipper)>::type>
  40             unused_skipper_type;
  41             unused_skipper_type unused_skipper(skipper);
  42
  43             return this->subject.parse(
  44                 first, last
  45               , make_context<skipper_tag>(unused_skipper, context)
  46               , rcontext
  47               , attr);
  48         }
  49
  50         template <typename Iterator, typename Context
  51           , typename RContext, typename Attribute>
  52         typename disable_if<has_skipper<Context>, bool>::type
  53         parse(Iterator& first, Iterator const& last
  54           , Context const& context, RContext& rcontext, Attribute& attr) const
  55         {
  56             //  no need to pre-skip if skipper is unused
  57             return this->subject.parse(
  58                 first, last
  59               , context
  60               , rcontext
  61               , attr);
  62         }
  63     };
  64
  65     struct lexeme_gen
  66     {
  67         template <typename Subject>
  68         lexeme_directive<typename extension::as_parser<Subject>::value_type>
  69         operator[](Subject const& subject) const
  70         {
  71             return { as_parser(subject) };
  72         }
  73     };
  74
  75     auto const lexeme = lexeme_gen{};
  76 }}}
  77
  78 #endif