260 lines
8.7 KiB
C++
260 lines
8.7 KiB
C++
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/*=============================================================================
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Copyright (c) 2003 Hartmut Kaiser
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http://spirit.sourceforge.net/
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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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#ifndef BOOST_SPIRIT_SWITCH_HPP
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#define BOOST_SPIRIT_SWITCH_HPP
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///////////////////////////////////////////////////////////////////////////////
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//
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// The default_p parser generator template uses the following magic number
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// as the corresponding case label value inside the generated switch()
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// statements. If this number conflicts with your code, please pick a
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// different one.
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//
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///////////////////////////////////////////////////////////////////////////////
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#if !defined(BOOST_SPIRIT_DEFAULTCASE_MAGIC)
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#define BOOST_SPIRIT_DEFAULTCASE_MAGIC 0x15F97A7
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#endif
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///////////////////////////////////////////////////////////////////////////////
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//
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// Spirit predefined maximum number of possible case_p/default_p case branch
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// parsers.
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//
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///////////////////////////////////////////////////////////////////////////////
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#if !defined(BOOST_SPIRIT_SWITCH_CASE_LIMIT)
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#define BOOST_SPIRIT_SWITCH_CASE_LIMIT 3
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#endif // !defined(BOOST_SPIRIT_SWITCH_CASE_LIMIT)
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///////////////////////////////////////////////////////////////////////////////
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#include <boost/static_assert.hpp>
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///////////////////////////////////////////////////////////////////////////////
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//
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// Ensure BOOST_SPIRIT_SELECT_LIMIT > 0
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//
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///////////////////////////////////////////////////////////////////////////////
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BOOST_STATIC_ASSERT(BOOST_SPIRIT_SWITCH_CASE_LIMIT > 0);
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#include <boost/spirit/home/classic/namespace.hpp>
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#include <boost/spirit/home/classic/core/config.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/spirit/home/classic/core/parser.hpp>
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#include <boost/spirit/home/classic/core/composite/epsilon.hpp>
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#include <boost/spirit/home/classic/dynamic/impl/switch.ipp>
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///////////////////////////////////////////////////////////////////////////////
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namespace boost { namespace spirit {
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BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
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///////////////////////////////////////////////////////////////////////////////
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//
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// The switch_parser allows to build switch like parsing constructs, which
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// will have much better performance as comparable straight solutions.
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//
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// Input stream driven syntax:
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//
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// switch_p
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// [
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// case_p<'a'>
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// (...parser to use, if the next character is 'a'...),
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// case_p<'b'>
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// (...parser to use, if the next character is 'b'...),
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// default_p
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// (...parser to use, if nothing was matched before...)
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// ]
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//
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// General syntax:
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//
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// switch_p(...lazy expression returning the switch condition value...)
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// [
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// case_p<1>
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// (...parser to use, if the switch condition value is 1...),
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// case_p<2>
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// (...parser to use, if the switch condition value is 2...),
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// default_p
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// (...parser to use, if nothing was matched before...)
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// ]
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//
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// The maximum number of possible case_p branches is defined by the p constant
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// BOOST_SPIRIT_SWITCH_CASE_LIMIT (this value defaults to 3 if not otherwise
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// defined).
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//
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///////////////////////////////////////////////////////////////////////////////
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template <typename CaseT, typename CondT = impl::get_next_token_cond>
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struct switch_parser
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: public unary<CaseT, parser<switch_parser<CaseT, CondT> > >
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{
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typedef switch_parser<CaseT, CondT> self_t;
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typedef unary_parser_category parser_category_t;
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typedef unary<CaseT, parser<self_t> > base_t;
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switch_parser(CaseT const &case_)
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: base_t(case_), cond(CondT())
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{}
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switch_parser(CaseT const &case_, CondT const &cond_)
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: base_t(case_), cond(cond_)
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{}
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template <typename ScannerT>
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struct result
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{
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typedef typename match_result<ScannerT, nil_t>::type type;
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};
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template <typename ScannerT>
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typename parser_result<self_t, ScannerT>::type
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parse(ScannerT const& scan) const
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{
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return this->subject().parse(scan,
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impl::make_cond_functor<CondT>::do_(cond));
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}
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CondT cond;
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};
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///////////////////////////////////////////////////////////////////////////////
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template <typename CondT>
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struct switch_cond_parser
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{
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switch_cond_parser(CondT const &cond_)
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: cond(cond_)
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{}
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template <typename ParserT>
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switch_parser<ParserT, CondT>
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operator[](parser<ParserT> const &p) const
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{
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return switch_parser<ParserT, CondT>(p.derived(), cond);
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}
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CondT const &cond;
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};
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///////////////////////////////////////////////////////////////////////////////
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template <int N, typename ParserT, bool IsDefault>
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struct case_parser
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: public unary<ParserT, parser<case_parser<N, ParserT, IsDefault> > >
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{
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typedef case_parser<N, ParserT, IsDefault> self_t;
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typedef unary_parser_category parser_category_t;
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typedef unary<ParserT, parser<self_t> > base_t;
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typedef typename base_t::subject_t self_subject_t;
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BOOST_STATIC_CONSTANT(int, value = N);
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BOOST_STATIC_CONSTANT(bool, is_default = IsDefault);
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BOOST_STATIC_CONSTANT(bool, is_simple = true);
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BOOST_STATIC_CONSTANT(bool, is_epsilon = (
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is_default && boost::is_same<self_subject_t, epsilon_parser>::value
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));
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case_parser(parser<ParserT> const &p)
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: base_t(p.derived())
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{}
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template <typename ScannerT>
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struct result
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{
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typedef typename match_result<ScannerT, nil_t>::type type;
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};
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template <typename ScannerT, typename CondT>
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typename parser_result<self_t, ScannerT>::type
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parse(ScannerT const& scan, CondT const &cond) const
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{
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typedef impl::default_case<self_t> default_t;
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if (!scan.at_end()) {
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typedef impl::default_delegate_parse<
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value, is_default, default_t::value> default_parse_t;
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typename ScannerT::iterator_t const save(scan.first);
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return default_parse_t::parse(cond(scan), *this,
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*this, scan, save);
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}
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return default_t::is_epsilon ? scan.empty_match() : scan.no_match();
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}
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template <int N1, typename ParserT1, bool IsDefault1>
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impl::compound_case_parser<
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self_t, case_parser<N1, ParserT1, IsDefault1>, IsDefault1
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>
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operator, (case_parser<N1, ParserT1, IsDefault1> const &p) const
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{
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// If the following compile time assertion fires, you've probably used
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// more than one default_p case inside the switch_p parser construct.
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BOOST_STATIC_ASSERT(!is_default || !IsDefault1);
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typedef case_parser<N1, ParserT1, IsDefault1> right_t;
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return impl::compound_case_parser<self_t, right_t, IsDefault1>(*this, p);
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}
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};
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///////////////////////////////////////////////////////////////////////////////
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struct switch_parser_gen {
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// This generates a switch parser, which is driven by the condition value
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// returned by the lazy parameter expression 'cond'. This may be a parser,
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// which result is used or a phoenix actor, which will be dereferenced to
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// obtain the switch condition value.
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template <typename CondT>
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switch_cond_parser<CondT>
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operator()(CondT const &cond) const
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{
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return switch_cond_parser<CondT>(cond);
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}
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// This generates a switch parser, which is driven by the next character/token
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// found in the input stream.
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template <typename CaseT>
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switch_parser<CaseT>
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operator[](parser<CaseT> const &p) const
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{
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return switch_parser<CaseT>(p.derived());
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}
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};
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switch_parser_gen const switch_p = switch_parser_gen();
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///////////////////////////////////////////////////////////////////////////////
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template <int N, typename ParserT>
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inline case_parser<N, ParserT, false>
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case_p(parser<ParserT> const &p)
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{
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return case_parser<N, ParserT, false>(p);
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}
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///////////////////////////////////////////////////////////////////////////////
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struct default_parser_gen
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: public case_parser<BOOST_SPIRIT_DEFAULTCASE_MAGIC, epsilon_parser, true>
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{
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default_parser_gen()
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: case_parser<BOOST_SPIRIT_DEFAULTCASE_MAGIC, epsilon_parser, true>
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(epsilon_p)
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{}
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template <typename ParserT>
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case_parser<BOOST_SPIRIT_DEFAULTCASE_MAGIC, ParserT, true>
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operator()(parser<ParserT> const &p) const
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{
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return case_parser<BOOST_SPIRIT_DEFAULTCASE_MAGIC, ParserT, true>(p);
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}
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};
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default_parser_gen const default_p = default_parser_gen();
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///////////////////////////////////////////////////////////////////////////////
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BOOST_SPIRIT_CLASSIC_NAMESPACE_END
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}} // namespace BOOST_SPIRIT_CLASSIC_NS
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#endif // BOOST_SPIRIT_SWITCH_HPP
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