| /*============================================================================= |
| Copyright (c) 2001-2010 Joel de Guzman |
| |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| =============================================================================*/ |
| #if !defined(SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM) |
| #define SPIRIT_DIFFERENCE_FEBRUARY_11_2007_1250PM |
| |
| #if defined(_MSC_VER) |
| #pragma once |
| #endif |
| |
| #include <boost/spirit/home/qi/domain.hpp> |
| #include <boost/spirit/home/qi/meta_compiler.hpp> |
| #include <boost/spirit/home/qi/parser.hpp> |
| #include <boost/spirit/home/qi/detail/attributes.hpp> |
| #include <boost/spirit/home/support/info.hpp> |
| #include <boost/fusion/include/at.hpp> |
| |
| namespace boost { namespace spirit |
| { |
| /////////////////////////////////////////////////////////////////////////// |
| // Enablers |
| /////////////////////////////////////////////////////////////////////////// |
| template <> |
| struct use_operator<qi::domain, proto::tag::minus> // enables - |
| : mpl::true_ {}; |
| }} |
| |
| namespace boost { namespace spirit { namespace qi |
| { |
| template <typename Left, typename Right> |
| struct difference : binary_parser<difference<Left, Right> > |
| { |
| typedef Left left_type; |
| typedef Right right_type; |
| |
| template <typename Context, typename Iterator> |
| struct attribute |
| { |
| typedef typename |
| traits::attribute_of<left_type, Context, Iterator>::type |
| type; |
| }; |
| |
| difference(Left const& left, Right const& right) |
| : left(left), right(right) {} |
| |
| template <typename Iterator, typename Context |
| , typename Skipper, typename Attribute> |
| bool parse(Iterator& first, Iterator const& last |
| , Context& context, Skipper const& skipper |
| , Attribute& attr) const |
| { |
| // Unlike classic Spirit, with this version of difference, the rule |
| // lit("policeman") - "police" will always fail to match. |
| |
| // Spirit2 does not count the matching chars while parsing and |
| // there is no reliable and fast way to check if the LHS matches |
| // more than the RHS. |
| |
| // Try RHS first |
| Iterator start = first; |
| if (right.parse(first, last, context, skipper, unused)) |
| { |
| // RHS succeeds, we fail. |
| first = start; |
| return false; |
| } |
| // RHS fails, now try LHS |
| return left.parse(first, last, context, skipper, attr); |
| } |
| |
| template <typename Context> |
| info what(Context& context) const |
| { |
| return info("difference", |
| std::make_pair(left.what(context), right.what(context))); |
| } |
| |
| Left left; |
| Right right; |
| }; |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Parser generators: make_xxx function (objects) |
| /////////////////////////////////////////////////////////////////////////// |
| template <typename Elements, typename Modifiers> |
| struct make_composite<proto::tag::minus, Elements, Modifiers> |
| : make_binary_composite<Elements, difference> |
| {}; |
| }}} |
| |
| namespace boost { namespace spirit { namespace traits |
| { |
| template <typename Left, typename Right> |
| struct has_semantic_action<qi::difference<Left, Right> > |
| : binary_has_semantic_action<Left, Right> {}; |
| }}} |
| |
| #endif |