ceph/src/boost/libs/spirit/include/boost/spirit/home/qi/operator/difference.hpp

   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 #if !defined(SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM)
   8 #define SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM
   9
  10 #if defined(_MSC_VER)
  11 #pragma once
  12 #endif
  13
  14 #include <boost/spirit/home/qi/domain.hpp>
  15 #include <boost/spirit/home/qi/meta_compiler.hpp>
  16 #include <boost/spirit/home/qi/parser.hpp>
  17 #include <boost/spirit/home/qi/detail/attributes.hpp>
  18 #include <boost/spirit/home/support/info.hpp>
  19 #include <boost/spirit/home/support/has_semantic_action.hpp>
  20 #include <boost/spirit/home/support/handles_container.hpp>
  21 #include <boost/fusion/include/at.hpp>
  22
  23 namespace boost { namespace spirit
  24 {
  25     ///////////////////////////////////////////////////////////////////////////
  26     // Enablers
  27     ///////////////////////////////////////////////////////////////////////////
  28     template <>
  29     struct use_operator<qi::domain, proto::tag::minus> // enables -
  30       : mpl::true_ {};
  31 }}
  32
  33 namespace boost { namespace spirit { namespace qi
  34 {
  35     template <typename Left, typename Right>
  36     struct difference : binary_parser<difference<Left, Right> >
  37     {
  38         typedef Left left_type;
  39         typedef Right right_type;
  40
  41         template <typename Context, typename Iterator>
  42         struct attribute
  43         {
  44             typedef typename
  45                 traits::attribute_of<left_type, Context, Iterator>::type
  46             type;
  47         };
  48
  49         difference(Left const& left_, Right const& right_)
  50           : left(left_), right(right_) {}
  51
  52         template <typename Iterator, typename Context
  53           , typename Skipper, typename Attribute>
  54         bool parse(Iterator& first, Iterator const& last
  55           , Context& context, Skipper const& skipper
  56           , Attribute& attr_) const
  57         {
  58             // Unlike classic Spirit, with this version of difference, the rule
  59             // lit("policeman") - "police" will always fail to match.
  60
  61             // Spirit2 does not count the matching chars while parsing and
  62             // there is no reliable and fast way to check if the LHS matches
  63             // more than the RHS.
  64
  65             // Try RHS first
  66             Iterator start = first;
  67             if (right.parse(first, last, context, skipper, unused))
  68             {
  69                 // RHS succeeds, we fail.
  70                 first = start;
  71                 return false;
  72             }
  73             // RHS fails, now try LHS
  74             return left.parse(first, last, context, skipper, attr_);
  75         }
  76
  77         template <typename Context>
  78         info what(Context& context) const
  79         {
  80             return info("difference",
  81                 std::make_pair(left.what(context), right.what(context)));
  82         }
  83
  84         Left left;
  85         Right right;
  86     };
  87
  88     ///////////////////////////////////////////////////////////////////////////
  89     // Parser generators: make_xxx function (objects)
  90     ///////////////////////////////////////////////////////////////////////////
  91     template <typename Elements, typename Modifiers>
  92     struct make_composite<proto::tag::minus, Elements, Modifiers>
  93       : make_binary_composite<Elements, difference>
  94     {};
  95 }}}
  96
  97 namespace boost { namespace spirit { namespace traits
  98 {
  99     ///////////////////////////////////////////////////////////////////////////
 100     template <typename Left, typename Right>
 101     struct has_semantic_action<qi::difference<Left, Right> >
 102       : binary_has_semantic_action<Left, Right> {};
 103
 104     ///////////////////////////////////////////////////////////////////////////
 105     template <typename Left, typename Right, typename Attribute
 106       , typename Context, typename Iterator>
 107     struct handles_container<qi::difference<Left, Right>, Attribute, Context
 108       , Iterator>
 109       : binary_handles_container<Left, Right, Attribute, Context, Iterator> {};
 110 }}}
 111
 112 #endif