92 lines
3.1 KiB
C++
Executable File
92 lines
3.1 KiB
C++
Executable File
/*=============================================================================
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Copyright (c) 2001-2007 Joel de Guzman
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#if !defined(SPIRIT_DIFFERENCE_FEB_11_2007_1250PM)
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#define SPIRIT_DIFFERENCE_FEB_11_2007_1250PM
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#include <boost/spirit/home/qi/domain.hpp>
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#include <boost/spirit/home/support/component.hpp>
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#include <boost/spirit/home/support/attribute_of.hpp>
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#include <vector>
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namespace boost { namespace spirit { namespace qi
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{
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struct difference
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{
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template <typename Component, typename Context, typename Iterator>
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struct attribute
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{
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typedef typename
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result_of::left<Component>::type
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left_type;
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typedef typename
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traits::attribute_of<
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qi::domain, left_type, Context, Iterator>::type
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type;
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};
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template <
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typename Component
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, typename Iterator, typename Context
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, typename Skipper, typename Attribute>
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static bool parse(
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Component const& component
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, Iterator& first, Iterator const& last
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, Context& context, Skipper const& skipper
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, Attribute& attr)
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{
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typedef typename
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result_of::left<Component>::type::director
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ldirector;
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typedef typename
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result_of::right<Component>::type::director
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rdirector;
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// Unlike classic Spirit, with this version of difference, the rule
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// lit("policeman") - "police" will always fail to match.
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// Spirit2 does not count the matching chars while parsing and
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// there is no reliable and fast way to check if the LHS matches
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// more than the RHS.
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// Try RHS first
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Iterator start = first;
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if (rdirector::parse(right(component), first, last, context, skipper, unused))
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{
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// RHS succeeds, we fail.
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first = start;
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return false;
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}
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// RHS fails, now try LHS
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return ldirector::parse(left(component), first, last, context, skipper, attr);
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}
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template <typename Component, typename Context>
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static std::string what(Component const& component, Context const& ctx)
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{
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std::string result = "difference[";
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typedef typename
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result_of::left<Component>::type::director
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ldirector;
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typedef typename
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result_of::right<Component>::type::director
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rdirector;
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result += ldirector::what(left(component), ctx);
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result += ", ";
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result += rdirector::what(right(component), ctx);
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result += "]";
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return result;
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}
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};
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}}}
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#endif
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