Chris@16: /*=============================================================================
Chris@16:     Copyright (c) 2001-2011 Joel de Guzman
Chris@16: 
Chris@16:     Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16:     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: =============================================================================*/
Chris@16: #if !defined(SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM)
Chris@16: #define SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/spirit/home/qi/domain.hpp>
Chris@16: #include <boost/spirit/home/qi/meta_compiler.hpp>
Chris@16: #include <boost/spirit/home/qi/parser.hpp>
Chris@16: #include <boost/spirit/home/qi/detail/attributes.hpp>
Chris@16: #include <boost/spirit/home/support/info.hpp>
Chris@16: #include <boost/spirit/home/support/has_semantic_action.hpp>
Chris@16: #include <boost/spirit/home/support/handles_container.hpp>
Chris@16: #include <boost/fusion/include/at.hpp>
Chris@16: 
Chris@16: namespace boost { namespace spirit
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     // Enablers
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <>
Chris@16:     struct use_operator<qi::domain, proto::tag::minus> // enables -
Chris@16:       : mpl::true_ {};
Chris@16: }}
Chris@16: 
Chris@16: namespace boost { namespace spirit { namespace qi
Chris@16: {
Chris@16:     template <typename Left, typename Right>
Chris@16:     struct difference : binary_parser<difference<Left, Right> >
Chris@16:     {
Chris@16:         typedef Left left_type;
Chris@16:         typedef Right right_type;
Chris@16: 
Chris@16:         template <typename Context, typename Iterator>
Chris@16:         struct attribute
Chris@16:         {
Chris@16:             typedef typename
Chris@16:                 traits::attribute_of<left_type, Context, Iterator>::type
Chris@16:             type;
Chris@16:         };
Chris@16: 
Chris@16:         difference(Left const& left_, Right const& right_)
Chris@16:           : left(left_), right(right_) {}
Chris@16: 
Chris@16:         template <typename Iterator, typename Context
Chris@16:           , typename Skipper, typename Attribute>
Chris@16:         bool parse(Iterator& first, Iterator const& last
Chris@16:           , Context& context, Skipper const& skipper
Chris@16:           , Attribute& attr_) const
Chris@16:         {
Chris@16:             // Unlike classic Spirit, with this version of difference, the rule
Chris@16:             // lit("policeman") - "police" will always fail to match.
Chris@16: 
Chris@16:             // Spirit2 does not count the matching chars while parsing and
Chris@16:             // there is no reliable and fast way to check if the LHS matches
Chris@16:             // more than the RHS.
Chris@16: 
Chris@16:             // Try RHS first
Chris@16:             Iterator start = first;
Chris@16:             if (right.parse(first, last, context, skipper, unused))
Chris@16:             {
Chris@16:                 // RHS succeeds, we fail.
Chris@16:                 first = start;
Chris@16:                 return false;
Chris@16:             }
Chris@16:             // RHS fails, now try LHS
Chris@16:             return left.parse(first, last, context, skipper, attr_);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Context>
Chris@16:         info what(Context& context) const
Chris@16:         {
Chris@16:             return info("difference",
Chris@16:                 std::make_pair(left.what(context), right.what(context)));
Chris@16:         }
Chris@16: 
Chris@16:         Left left;
Chris@16:         Right right;
Chris@16:     };
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     // Parser generators: make_xxx function (objects)
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Elements, typename Modifiers>
Chris@16:     struct make_composite<proto::tag::minus, Elements, Modifiers>
Chris@16:       : make_binary_composite<Elements, difference>
Chris@16:     {};
Chris@16: }}}
Chris@16: 
Chris@16: namespace boost { namespace spirit { namespace traits
Chris@16: {
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Left, typename Right>
Chris@16:     struct has_semantic_action<qi::difference<Left, Right> >
Chris@16:       : binary_has_semantic_action<Left, Right> {};
Chris@16: 
Chris@16:     ///////////////////////////////////////////////////////////////////////////
Chris@16:     template <typename Left, typename Right, typename Attribute
Chris@16:       , typename Context, typename Iterator>
Chris@16:     struct handles_container<qi::difference<Left, Right>, Attribute, Context
Chris@16:       , Iterator>
Chris@16:       : binary_handles_container<Left, Right, Attribute, Context, Iterator> {};
Chris@16: }}}
Chris@16: 
Chris@16: #endif