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259 lines
8.7 KiB
259 lines
8.7 KiB
/*============================================================================= |
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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 perfomance 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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