148 lines
4.9 KiB
Plaintext
148 lines
4.9 KiB
Plaintext
/*=============================================================================
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Copyright (c) 1998-2003 Joel de Guzman
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Copyright (c) 2001 Daniel Nuffer
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Copyright (c) 2002 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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#if !defined(BOOST_SPIRIT_ALTERNATIVE_HPP)
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#define BOOST_SPIRIT_ALTERNATIVE_HPP
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#include <boost/spirit/home/classic/namespace.hpp>
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#include <boost/spirit/home/classic/core/parser.hpp>
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#include <boost/spirit/home/classic/core/primitives/primitives.hpp>
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#include <boost/spirit/home/classic/core/composite/composite.hpp>
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#include <boost/spirit/home/classic/meta/as_parser.hpp>
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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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// alternative class
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//
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// Handles expressions of the form:
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//
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// a | b
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//
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// where a and b are parsers. The expression returns a composite
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// parser that matches a or b. One (not both) of the operands may
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// be a literal char, wchar_t or a primitive string char const*,
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// wchar_t const*.
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//
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// The expression is short circuit evaluated. b is never touched
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// when a is returns a successful match.
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//
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///////////////////////////////////////////////////////////////////////////
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struct alternative_parser_gen;
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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#pragma warning(push)
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#pragma warning(disable:4512) //assignment operator could not be generated
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#endif
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template <typename A, typename B>
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struct alternative
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: public binary<A, B, parser<alternative<A, B> > >
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{
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typedef alternative<A, B> self_t;
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typedef binary_parser_category parser_category_t;
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typedef alternative_parser_gen parser_generator_t;
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typedef binary<A, B, parser<self_t> > base_t;
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alternative(A const& a, B const& b)
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: base_t(a, b) {}
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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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typedef typename parser_result<self_t, ScannerT>::type result_t;
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typedef typename ScannerT::iterator_t iterator_t;
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{ // scope for save
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iterator_t save = scan.first;
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if (result_t hit = this->left().parse(scan))
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return hit;
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scan.first = save;
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}
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return this->right().parse(scan);
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}
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};
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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#pragma warning(pop)
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#endif
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struct alternative_parser_gen
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{
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template <typename A, typename B>
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struct result
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{
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typedef
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alternative<
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typename as_parser<A>::type
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, typename as_parser<B>::type
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>
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type;
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};
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template <typename A, typename B>
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static alternative<
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typename as_parser<A>::type
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, typename as_parser<B>::type
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>
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generate(A const& a, B const& b)
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{
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return alternative<BOOST_DEDUCED_TYPENAME as_parser<A>::type,
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BOOST_DEDUCED_TYPENAME as_parser<B>::type>
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(as_parser<A>::convert(a), as_parser<B>::convert(b));
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}
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};
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template <typename A, typename B>
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alternative<A, B>
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operator|(parser<A> const& a, parser<B> const& b);
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template <typename A>
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alternative<A, chlit<char> >
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operator|(parser<A> const& a, char b);
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template <typename B>
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alternative<chlit<char>, B>
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operator|(char a, parser<B> const& b);
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template <typename A>
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alternative<A, strlit<char const*> >
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operator|(parser<A> const& a, char const* b);
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template <typename B>
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alternative<strlit<char const*>, B>
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operator|(char const* a, parser<B> const& b);
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template <typename A>
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alternative<A, chlit<wchar_t> >
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operator|(parser<A> const& a, wchar_t b);
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template <typename B>
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alternative<chlit<wchar_t>, B>
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operator|(wchar_t a, parser<B> const& b);
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template <typename A>
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alternative<A, strlit<wchar_t const*> >
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operator|(parser<A> const& a, wchar_t const* b);
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template <typename B>
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alternative<strlit<wchar_t const*>, B>
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operator|(wchar_t const* a, parser<B> const& b);
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BOOST_SPIRIT_CLASSIC_NAMESPACE_END
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}} // namespace BOOST_SPIRIT_CLASSIC_NS
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#endif
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#include <boost/spirit/home/classic/core/composite/impl/alternative.ipp>
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